FOUS11 KWBC 271911
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
311 PM EDT Mon Apr 27 2026

Valid 00Z Tue Apr 28 2026 - 00Z Fri May 01 2026

...Central Rockies...
Days 1 & 3...

Fast moving shortwave with modest amplitude will race E/NE from the
Great Basin to the Central Rockies before reaching the Central
Plains by 00Z/Wednesday (end of D1). Downstream of this impulse,
persistent but weak 700mb WAA will surge moisture into the Central
Rockies, especially north-central Colorado, leading to periods of
light to moderate snowfall the first half of D1 before forcing
ejects to the east. Snow levels during this time will fall beneath
the translating impulse, but remain above 7000 ft, suggesting that
any impacted travel will only be across the higher passes of the CO
Rockies. This is reflected additionally by WPC probabilities that
are above 50% for 6+ inches of snow only across the Park Range and
Medicine Bow Range, with lesser amounts expected elsewhere.

After a break on D2, a more substantial impulse will lift across
the region D3 bringing renewed snowfall once again to the higher
elevations. This second system begins as a closed mid-level low
near Baja Wednesday evening, but then quickly opens and ejects east
into the Desert Southwest by the end of the forecast period /00Z
Friday/. While the direct height falls and PVA from this impulse
will remain SW of the region on D3, increasingly impressive 700mb
warm and moist advection surging northward ahead of this wave will
interact with additional downstream mid-level divergence to push
mid-level ascent over the CO Rockies once again. At the same time,
easterly low-level flow will advect increasing moisture (with
upslope enhancement) into CO from the Gulf/Southern Plains. This
will result in expanding precipitation, especially the latter half
of D3, with snow falling above 8000 ft. This could end up as a
significant high-elevation snow event continuing into D4, but for
D3, current WPC probabilities are high (>70%) for 6+ inches only
in the higher Front Range, including Pike's Peak, and portions of
the Sangre de Cristos.


The probability for significant icing over one-tenth of an inch is
less than 10 percent.


Weiss


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FOUS11 KWBC 280732
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
332 AM EDT Tue Apr 28 2026

Valid 12Z Tue Apr 28 2026 - 12Z Fri May 01 2026

...Central & Southern Rockies...
Days 1-3...

Periods of light-to-moderate snow will linger for a little longer
this morning with an additional 3-6" of snowfall possible in the
Park Range and Flat Tops of the CO Rockies. Snow should taper off
after midday as the shortwave trough responsible for the mountain
snow moves into the Central Plains.

Following a break in the action between Tuesday afternoon and
Wednesday evening, a closed 500mb low (closed at 300mb as well)
west of Baja will head east at the same time that a secondary
impulse over the Great Basin results in 500mb height falls over the
CO Rockies. This "squeeze-play" between the pair of upper-level
troughs and a 500mb ridge over Mexico fosters a robust subtropical
stream, culminating in 200mb winds over the Central Plains that
exceed the 99.5 climatological percentile per ECMWF SATs. In
addition to this textbook jet-streak dynamics setup, high pressure
over the Northern Plains will bleed south down the Front Range and
Sangre De Cristo, forcing favorable easterly upsloping low-level
winds to ensue. This is a classic setup for mountain snow (and
valley/Plains rainfall) in a region that could sorely use any
precipitation of note.

The latest forecast shows snow increasing in intensity along the CO
Front Range throughout the day on Thursday, then along the Sangre
De Cristo Thursday afternoon into Thursday night. There remain some
differences in model guidance regarding the timing and strength of
the approaching 500mb low as it tracks over northern Mexico Friday
morning. Regardless, low-level easterly flow should linger long
enough into Friday to keep mountain snow going through at least the
first half of the day. Most guidance agrees snow tapers off by
Friday evening as the 500mb low races east into the Southern
Plains. WPC probabilities show at least moderate chances (>50%) for
snowfall totals >8" above 9,000ft in the CO Front Range and Sangre
De Cristo, with the Park Range having similar probabilities above
10,000ft. Some of the tallest CO peaks (including Pikes Peak) could
witness localized snowfall amounts surpass 20". Some light snow is
possible over the Palmer Divide and Raton Pass (1-3"), but most
snow is a welcomed sight for drought-stricken CO and NM.


The probability for significant icing over one-tenth of an inch is
less than 10 percent.


Mullinax




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FOUS11 KWBC 281813
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
213 PM EDT Tue Apr 28 2026

Valid 00Z Wed Apr 29 2026 - 00Z Sat May 02 2026

...Central & Southern Rockies...
Days 2-3...

Two distinct mid-level impulses will interact as they move across
the Great Basin and into the Central Rockies to bring heavy snow to
the higher elevations of CO and NM. During the past few model runs
the trends have been for more substantial snow but with a farther
south footprint, with significant accumulations now expected to
miss Wyoming, but affect Colorado and New Mexico Wednesday night
through Friday night.

At the beginning of the period /00Z Wednesday/ these impulses will
be positioned over CA, and west of Baja, respectively. Throughout
D1, the lead impulse over CA will open and become embedded in the
larger trough over the Great Basin, while the stronger impulse
(really a cutoff low) will hang back and move little until opening
on Thursday as it drifts eastward over Baja. As this secondary
evolution occurs, the result will be a longwave positively tilted
trough anchored NE to SW across the Central and Southern Rockies,
with 500mb heights falling below the 10th percentile within the
CFSR database across the Desert Southwest. This evolution will
result in broad height falls and the amplification of an
impressive subtropical jet streak arching from the Four Corners
into the Ohio Valley. Where the LFQ of this jet streak overlaps
with the height falls, broad synoptic lift will occur, likely
focused over CO and NM.

At the same time, since the primary trough axis will lag to the
west during this forecast period, persistent SW flow within the
700-500mb layer will transport moisture northeastward, and while
the core of the IVT will remain south of the Four Corners, there
will be sufficient moisture to result in heavy precipitation.

The heaviest precipitation is likely in the upslope regions of the
east-facing terrain thanks to easterly flow behind a cold front,
but modest fgen and continued mid-level isentropic ascent will also
expand precipitation across much of CO and NM by 00Z-06Z Friday.
Snow levels through the event will remain elevated, generally
around 8000 ft, but may periodically fall to 7000 ft through a
combination of precipitation loading/dynamic cooling, lowering
heights aloft, and CAA behind the cold front. This will allow for
some light accumulations even out onto the Palmer Divide and Raton
Mesa. However, the heaviest snowfall is likely in the higher
elevations along the Front Range, Sangre de Cristos, and as far
west as the San Juans. 2-day WPC probabilities are high for more
than 12 inches of snow are high (>70%) in the higher elevations of
the Front Range, including the Pike's Peak region, and along the
Sangre de Cristos. Lower elevations will have less snow, but I-25
will also likely experience some modest accumulations where it
crosses the Palmer Divide and Raton Mesa as reflected by WPC
probabilities for 4+ inches in these areas that rise to 30-50%.


The probability for significant icing over one-tenth of an inch is
less than 10 percent.


Weiss

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FOUS11 KWBC 290722
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
322 AM EDT Wed Apr 29 2026

Valid 12Z Wed Apr 29 2026 - 12Z Sat May 02 2026

...Central & Southern Rockies...
Days 1-3...

A pair of upper-level disturbances; one over the Great Basin and
another approaching the Central Rockies from the north, will work
together to produce a much-needed period of moderate-to-heavy
mountain snow from the WY Rockies on south through the CO/northern
NM Rockies. As these disturbances work together to gradually cause
500mb height falls, a robust 130kt 250mb jet streak will tap into
subtropical moisture at the same time that high pressure building
in over the Northern Plains forces easterly upslope flow into the
Front Range and Sangre De Cristo. Periods of light high-elevation
mountain snow (generally above 9,000ft) will occur Wednesday night,
but as the strong upsloping easterly winds arrive on Thursday,
snowfall rates will intensify along the Front and Park Ranges. The
Palmer Divide above 7,000ft is also likely to see periods of snow
Thursday afternoon, potentially causing some slick travel
conditions as the sun sets Thursday evening. Snowfall rates between
1-2"/hr are likely along the Front Range and Sangre De Cristo
above 9,000 Thursday afternoon and into Thursday night. Snowfall
rates diminish gradually Friday as easterly upslope flow gradually
lessens, but still manages to keep periods of snow in the forecast
for much of the day. A burst of heavier snowfall is likely along
the San Juans above 10,000ft as the trailing 500mb shortwave trough
pivots through the Four Corners region on Friday. Snow finally
tapers off some time Friday night.

WPC probabilities paint a snowy picture over the Central and
Southern Rockies, which is overall a great thing to see given the
ongoing drought and lack of snowpack. The heavier snowfall totals

12") are most likely to occur above 8,000ft along the Front

Range, the above 9,000ft along the Park Range and the Sangre De
Cristo. Some localized totals >20" are possible in the more remote
peaks pf the CO Rockies, including Pike's Peak. Generally 6-12" of
snowfall are likely along the San Juans above 11,000ft. The WSSI
does show mostly Minor Impacts at elevations between
8,000-10,000ft, with localized Moderate to Major Impacts at the
more remote elevations above 10,000ft. Some Minor Impacts are
depicted along I-25 over the Palmer Divide and Raton Pass, so some
locally hazardous travel conditions are possible Thursday
afternoon and evening.

Farther north, some light-to-moderatwe snowfall is likely in the WY
mountain ranges such as the Wind River, Big Horn, and Absaroka.
Most totals will range between 4-8" above 9,000ft with localized
amounts approaching 10" possible. The bulk of the snowfall there
occurs today, although some light snowfall looks to persist into
the first half of Thursday.


The probability for significant icing over one-tenth of an inch is
less than 10 percent.


Mullinax




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FOUS11 KWBC 291814
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
214 PM EDT Wed Apr 29 2026

Valid 00Z Thu Apr 30 2026 - 00Z Sun May 03 2026

...Central & Southern Rockies...
Days 1-3...

Expansive surface high pressure digging through the middle of the
country will drive a strong cold front southward all the way to the
Mexican border and Gulf Coast. Behind this front, cool air will
flood through the middle of the country, with post-frontal easterly
flow banking into the Central Rockies beginning Wednesday night and
persisting through Thursday to produce upslope flow into the
terrain.

As this occurs, synoptic ascent will begin to intensify over the
Central Rockies as well in response to interacting mid-level
impulses forcing a positively tilted, longwave trough, to drift
east late this week and into the weekend. This will force ascent
through height falls and the diffluent LFQ of a corresponding
subtropical jet streak pushing eastward across the southern tier of
the CONUS. Additionally, since the trough axis lags to the west,
moisture will continually funnel overhead on mid-level SW flow from
the Pacific, manifesting as large areas of precipitation where
forcing overlaps this moisture plume.

This precipitation will fall in the form of snow above generally
8000 ft, but locally snow levels could fall to below 7000 ft at
times, especially during the period of heaviest precipitation or as
the trough axis swings overhead to lower thicknesses. This will
keep the heaviest snowfall accumulations outside of the populated
I-25 corridor of CO/NM, except in the higher elevations of the
Palmer Divide and Raton Mesa where some light snowfall is expected
as reflected by WPC probabilities that are generally 50-70% for 4+
inches in these areas. This will result in hazardous driving across
these portions of I-25 as reflected by 30-50% probabilities of at
least minor impacts from the WSSI-P.

The heaviest accumulations, which are expected (>70% chance) to
exceed 12 inches before snow wanes quickly Friday evening, are
forecast in the higher elevations of the Front Range and Sangre de
Cristo Mountains, as well as the eastern portions of the San Juans.
Locally 2+ feet is possible (10-30% chance) in the highest peaks,
including Pike's Peak and along the Wet Mountains west of Pueblo,
CO.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Weiss

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FOUS11 KWBC 300807
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
407 AM EDT Thu Apr 30 2026

Valid 12Z Thu Apr 30 2026 - 12Z Sun May 03 2026

...Southern Rockies...
Days 1-2...

Surface high pressure over the central Great Plains provides some
return flow and moisture up the southern High Plains to a frontal
boundary over Colorado Rockies through today where mountain snow
persists. Upper low pressure currently off the northern Baja
crosses south of Arizona tonight aiding lift over southern NM with
additional lift for the southern Rockies in northern NM. Snow
levels remain 6000-7000ft in CO today with Day 1 snow probs for >6"
40-80% down central CO ranges from the Front Range through the
Sangre de Cristos. Snow levels in the San Juans and southern Sangre
de Cristos in northern NM drop from around 9000ft to 8000ft tonight
where Day 2 snow probs for >6" are 30-60%.

Snow levels remain 10,000ft or higher in southern NM with just rain
expected there on Friday. Precip shifts east of NM Friday afternoon
as the southern tier low opens into a progressive trough over
Texas.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Jackson



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FOUS11 KWBC 301850
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
250 PM EDT Thu Apr 30 2026

Valid 00Z Fri May 01 2026 - 00Z Mon May 04 2026

...Southern Rockies...
Days 1-2...

Cool high pressure digging across the Central Plains will sharpen
against the terrain of CO and NM providing impressive easterly flow
to drive upslope ascent into the mountains. At the same time, upper
troughing extending SW into the Great Basin will gradually shift
eastward, producing height falls, which will work together with a
strengthening zonally oriented jet streak to create deep layer lift
over the Central and Southern Rockies. This lift will act upon a
modestly moist column thanks to Pacific moisture streaming
eastward, resulting in periods of moderate to heavy snowfall from
the Front Range of CO through the San Juans and then down into the
Sangre de Cristos. The guidance has trended south and a bit
drier/weaker the past few model cycles, so while significant
accumulations are still likely, the heaviest snow will likely be
across the Wet Mountains and Sangre de Cristos where WPC
probabilities for more than 8 inches D1 are as high as 50-70%,
leading to storm total accumulations of 12-18 inches in these
areas. The heaviest snow will be above 8000 ft, but some minor
lowering to 6500-7000 ft will create some hazardous driving over
the elevated portions of I-25, primarily across the Palmer Divide
and Raton Mesa.

The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Weiss


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FOUS11 KWBC 010805
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
405 AM EDT Fri May 1 2026

Valid 12Z Fri May 01 2026 - 12Z Mon May 04 2026

...Southern Rockies...
Day 1...

A southern stream upper low south of Arizona is bringing rain to
southern NM/far west TX from convergence along a stalled front
ahead of the low. In the cold sector to the north, sfc high
pressure wedging into northeast NM is aiding lift on the Sangre de
Cristos where snow levels are around 7500ft. The sfc high
strengthens today as a shortwave trough currently over ID shifts
southeast over the Four Corners this afternoon and promotes
instability over the San Juans with snow levels around 8500ft. Day
1 snow probs for >4" additional after 12Z are 40-70% in the San
Juans and NM portion of the Sangre de Cristos. Mountain precip
diminishes late this evening as the shortwave trough axis shifts to
the Plains. across the Central Plains.


...Sierra Nevada...
Day 3...

A large, but overall weak low shifts onshore near the Bay Area
Sunday bringing some moist upslope flow to the Sierra Nevada.
Minor height falls allow Sierra Nevada snow levels to fall from
about 9500ft to 8500ft during the main round of precip Sunday
afternoon. Low precip rates, the high snow levels, and timing
during peak diurnal limits snow to the highest peaks of the
southern Sierra Nevada where Day 3 probs for >2" are around 20%.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Jackson




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FOUS11 KWBC 011755
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
155 PM EDT Fri May 1 2026

Valid 00Z Sat May 02 2026 - 00Z Tue May 05 2026

...Sierra Nevada...
Day 3...

A large mid-level low but with modest amplitude will swing onshore
central California Sunday night into Monday morning, producing
modest height falls across the area. At the same time, downstream
SW flow will transport increasing moisture into the region, with PW
anomalies progged to exceed the 90th percentile according to the
NAEFS ensemble tables. In general, forcing for ascent will
transient outside of upslope enhancement in the Sierra, with
periodic vorticity impulses leading to expanding precipitation.
Snow levels during this time will fall slowly from around 9000ft
to 8000ft, with locally lower snow levels to 7500ft possible at
times in response to briefly enhanced ascent on steep lapse rates
to pull down some colder air. However, the most significant snow
accumulations, which will still be modest at generally 2-4" (WPC
probabilities for more than 4 inches are just 10-30%) will remain
above 9000ft and above most of the passes.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Weiss


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FOUS11 KWBC 020807
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
407 AM EDT Sat May 2 2026

Valid 12Z Sat May 02 2026 - 12Z Tue May 05 2026

...Sierra Nevada...
Days 2/3...

A large, but modest amplitude mid-level low will swing onshore
central California Sunday night and drift to southern CA through
Monday night. Upslope precip begins Sunday afternoon, but snow
levels will be around 9500ft before dropping to around 8000ft late
Sunday night. Snow levels will then be around 7500ft under the low
on Monday when the precip should be the most consistent. Day 3 snow
probs for >6" are generally 40-70% for the High Sierra.


...Wyoming and Colorado...
Day 3...

Low pressure swings through western Ontario Sunday night with a
potent cold front sweeping down the Northern Plains in its wake.
A digging mid-level trough behind the front provides lift over an
existing frontal boundary ahead of the aforementioned low moving
over CA before the cold front shunts activity a bit farther south
on Tuesday. There is uncertainty in the placement of this frontal
zone with the GFS farther north in central WY and the EC remaining
farther south along the WY/CO border. The front should be fairly
stationary once it is set up, so there could be a decent duration
to precip with snow levels dropping to around 7000ft behind the
cold front. Day 3 snow probs for >6" are 30-60% in the Wind River
and Bighorn ranges as well as around 50% on the Laramie Mtns and
20-40% on the Front Range in northern CO. Decently heavy mountain
snow then persists through Tuesday, so more info is to come on this
system.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Jackson


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FOUS11 KWBC 021853
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
253 PM EDT Sat May 2 2026

Valid 00Z Sun May 03 2026 - 00Z Wed May 06 2026

...Sierra Nevada...
Days 2-3...

Broad upper low near 40N/130W (west of NorCal) this evening will
continue southward overnight then turn eastward and move into
central CA late Sunday night/early Monday. Modest moisture plume
will be focused south/east of the Sierra, but incoming height falls
and upslope will still yield light to modest snow for the High
Sierra starting Sunday afternoon. Snow levels will be high to start

9000ft) but then trend lower to around 7000-8000ft as the upper

low approaches and slowly passes through the region overnight
Monday into Tuesday. By the end of this forecast period, the upper
low is forecast to be nearing the Grand Canyon with lingering snow
over the Sierra and rising snow levels. WPC probabilities for at
least 6 inches of snow are >50% above about 8000-9500ft (north to
south).


...Wyoming and Colorado...
Day 3...

In response to building ridging into NW Canada Monday morning,
troughing will sink into the Northern Plains and the Great Lakes
with an attendant and strong cold front racing southward from
Montana into Wyoming. At the same time, the upper low over CA will
continue to favor SW flow across the Four Corners as the upper jet
arcs into the region. Precipitation will expand across WY and CO
Monday into Tuesday ahead of the cold front with high snow levels
initially >9000-10,000ft. By early Tuesday, cold front will push
southward through WY and eastern CO with snow levels lowering to
6000-7000ft behind the boundary that may slow and hang up along the
Divide, keeping snow levels >8000ft on the west side. Modest to
locally heavier snow could set up over parts of southern WY into
northern CO via easterly/upslope flow (e.g., Laramie and Medicine
Bow Mountains) with additional modest snow over the Bighorns and
Wind River Range. Snow will continue past the end of this forecast
period. Through 00Z Wed, WPC probabilities for at least 6 inches of
snow are >50% above 8000-9500ft in northern WY and above
8500-10,000ft in CO. For at least 2 inches of snow, WPC
probabilities are >50% to as low as 7000-8000ft along the WY/CO
border through the Medicine Bow Mountains.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Fracasso


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FOUS11 KWBC 030833
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
433 AM EDT Sun May 3 2026

Valid 12Z Sun May 03 2026 - 12Z Wed May 06 2026

...Sierra Nevada...
Days 1-2...

Broad, not that deep upper low off CA will drift toward the SF Bay
area through tonight, then drift to SoCal through Tuesday when it
opens to a trough and ejects east. Modest moisture plume will
interact with the Sierra Nevada from the south with precip onset
expected this afternoon. Snow levels initially around 9000ft drop
to around 8000ft late tonight. Day 1 snow probs for >6" are around
20% in the High Sierra. The south movement of the low brings
some prolonged flow to the Sierra Nevada with snow levels down to
around 7500ft. Day 2 snow probs for >6" are 40-60% across the High
Sierra.


...Wyoming and Colorado...
Days 2/3...

Strong ridging north of the CA low will amplify over the northeast
Pacific into the Yukon through tonight and promote troughing to
surge down the Canadian Prairies tonight and the northern Plains
Monday. Meanwhile the SWly jet downstream of the CA low will surge
to the central Plains Monday, aiding left exit dynamics.
Precipitation will expand over southern WY and northern CO Monday
afternoon into Tuesday ahead of the cold front with high snow
levels initially >9000-10,000ft. On Tuesday, the cold front (and
precip focus) will push south through eastern CO with snow levels
lowering to 6000-7000ft behind the boundary that will dam up east
of the Divide, keeping snow levels >8000ft on the west side.
Modest to locally heavier snow should set up over parts of
southern WY through CO via easterly/upslope flow (e.g., Laramie
and Medicine Bow Mountains) with additional modest snow over the
Bighorns and Wind River Range through Tuesday evening before
tapering off as the focus shifts east onto the Plains Wednesday.
Day 2 snow probs for >6" are 20-30% on the Wind River Range and
Bighorns and 30-60% on the south Laramie and CO Front Range. Day 3
snow probs for >6" are nearly identical for the Wind River/Bighorn
with greatly expanded coverage over south WY through central CO
Ranges down to the northern Sangre de Cristos. Probs for >12" are
40-70% along the Front Range in what will be an impactful storm
though should be mainly seen as beneficial/drought relief.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Jackson



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FOUS11 KWBC 031837
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
237 PM EDT Sun May 3 2026

Valid 00Z Mon May 04 2026 - 00Z Thu May 07 2026

...Sierra Nevada...
Days 1-2...

Upper low just offshore NorCal this evening will move inland
through central then southern CA and into AZ late Tuesday as it
weakens into a positively-tilted open wave. A modest plume of
moisture will intersect the Sierra and promote light to locally
modest snow for the higher elevations as snow levels start around
9000ft this afternoon. As the cold core moves inland, snow levels
will drop to around 8000ft. Snow will end by Tuesday evening as
heights begin to rise. WPC probabilities for at least 6 inches of
snow are >50% above about 8500-9500ft.


...Wyoming and Colorado...
Days 1-3...

Building upper ridging north of the CA upper low will amplify over
the northeast Pacific into NW Canada through Monday, promoting
downstream troughing to surge down the Canadian Prairies tonight
and the northern Plains Monday. Upper jet out of the subtropics
will arc across the Four Corners region and provide modest synoptic
lift over the region with light and mainly high elevation snow in
advance of a strong cold front. Snow levels initially

9000-10,000ft will crash behind the cold front on Tuesday as it

races southward. Snow levels will lower over eastern CO to
6000-7000ft behind the boundary that will dam up east of the
Divide, keeping snow levels >8000ft on the west side. Modest to
locally heavier snow should set up over parts of southern WY
through CO via easterly/upslope flow (e.g., Laramie and Medicine
Bow Mountains) with additional modest snow over the Bighorns and
Wind River Range through Tuesday evening before tapering off as the
focus shifts east onto the Plains Wednesday. WPC probabilities for
at least 8 inches of snow are >50% above about: 9000-10,000ft over
the Bighorns and Wind River Range, 7000ft from southern WY into
the CO Rockies, and 10,000-11,000ft in the northern Sangre de
Cristos. The highest amounts of snow -- at least 18 inches -- are
most likely above 10,000ft in CO which could cause moderate impacts
to travel via I-70 west of Denver across the Divide.

The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Fracasso



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FOUS11 KWBC 040859
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
459 AM EDT Mon May 4 2026

Valid 12Z Mon May 04 2026 - 12Z Thu May 07 2026

...Sierra Nevada...
Day 1...

Upper low just over SF Bay will drift southeast to southern CA
through Tuesday before opening and ejecting east over AZ Tuesday
night. A modest plume of moisture will intersect the Sierra and
promote light to locally modest snow for the higher elevations as
snow levels remain around 8500ft. Snow will end Tuesday evening as
heights begin to rise. Day 1 WPC snow probabilities for >6" are

50% above about 8500ft.

...Wyoming and Colorado...
Days 1-3...

Upper ridging continues to build north of the CA upper low and
extends into the Yukon today, promoting downstream troughing to
surge down the northern Plains through this afternoon. WSWly jet
out of the Pacific subtropics will arc across the Four Corners
region today and provide lift over the cold front that enters CO
tonight. Snow levels of 9000 to 10,000ft will crash behind the cold
front on Tuesday as it shifts southward. Snow levels will lower
over eastern CO to 6000-7000ft as the boundary dams up against east
of the Divide, keeping snow levels >8000ft on the west side.
Modest to locally heavier snow should set up over parts of
southern WY through CO via easterly/upslope flow (e.g., Laramie and
Medicine Bow Mountains) as the upper low pushing into central CA
promotes lee-side troughing on the Rockies and some delay to the
cold frontal passage. Precip shifts down the Rockies through Wednesday
night before shifting east onto the Plains.

Day 1 WPC probabilities for >6" of snow are 40-80% over the
highest Snowy Range in WY and Front Range in CO. Day 2 is the
busiest day with renewed snow in both WY and CO including onto the
High Plains/Denver and snow probs >8" 50-90% over the Front Range
and generally 40-80% for the Wind River, Park Range, Pikes Peak,
and higher portions of the Palmer Divide. Meanwhile snow probs for

4" are 20-40% over the CO High Plains. Day 3 snow probs highlight

the southward shift in the frontal pattern with 30-50% for >8" snow
in the Sangre de Cristos.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Jackson


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FOUS11 KWBC 041907
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
307 PM EDT Mon May 4 2026

Valid 00Z Tue May 05 2026 - 00Z Fri May 08 2026

...Wyoming and Colorado...
Days 1-3...

A late season winter storm will produce periods of heavy snow
through mid-week to not only the Central Rockies, but snow levels
will be low enough to deliver accumulating snowfall to the I-25
corridor Tuesday. The meteorological setup consists of a shortwave
trough associated with the polar jet stream over the Northern
Plains diving southward towards a positively tilted closed-low
associated with a robust subtropical jet stream in the Southwest.
200mb winds over southeast NM and much of NM are above the 97.5
climatological percentile per NAEFS, which is playing a big role in
the development of an IVT over southern NM and west TX that is
among the strongest for this time of year in the CFSR database. The
250mb jet streak associated with the polar jet will place its
divergent left-exit region over the southern WY and much of CO at
the same time Canadian high pressure building in from the north
causes enhanced upsloping easterly flow.

With no shortage of 850-300mb moisture, periods of snow will begin
to unfold tonight over the Front and Park Ranges of CO, as well as
the Medicine Bow and Laramie Ranges of WY. As the best upper-level
divergence moves in aloft on Tuesday and low-level winds
strengthen, precipitation rates will increase and snow levels will
crash to the valley floors in WY with snow beginning to accumulate
along the I-25/I-80 corridor in southern WY. By Tuesday afternoon
and evening, any rain will transition to snow from I-25 east of the
Flat Irons on south to the Palmer Divide. Snow will accumulate
more efficiently after sunset, which coincidentally will be when
the Denver/Boulder metro area is likely to witness its heaviest
burst of snow from this event. Snow is also expected to accumulate
along the I-70 corridor east of Denver and perhaps as far east as
far northeast KS. The WPC Snowband Probability Tracker shows
instances of 1-2"/hr snowfall rates over northern CO and far
southern WY, with some >3"/hr rates possible in the Front Range.
Snow will work its way south early Wednesday morning through the
Sangre De Cristo and San Juans as snowfall rates gradually diminish
from the Cheyenne/Fort Collins area. By Wednesday afternoon and
evening, only the Sangre De Cristo, San Juans, and Raton Mesa are
likely to see accumulating snowfall. Snow is likely to conclude in
the higher elevations of northern NM before sunrise on Thursday.

WPC probabilities highlight the stark contrast in these classic
late-season snow events, as well as the impacts of urban heat
islands. 24-hour probabilities for >6" of snow are generally
between 20-40% in the Denver metro, whereas at elevations >6,000ft
are over 50% for snowfall totals >6". Unsurprisingly, the mountain
ranges will be the big "winners" for this event. The CO Front
Range, including Rocky Mountain NP, sport high chances (>70%) for
snowfall amounts >18" for this event. In fact, Moderate-to-high
chances (50-80%) for snowfall totals >12" are present in the
Medicine Bow and Laramie Range of WY, as well as the Park Range and
the peaks of the Sangre De Cristo.

This winter storm will produce much needed snowfall in the drought-
stricken Central Rockies and High Plains. However, unlike last
week's event which had less snowfall and was confined to the higher
elevations, this event is more significant and will impacts both
commerce and infrastructure. The WSSI highlights widespread Minor
Impacts (winter driving conditions; use caution while driving) from
southeast WY to as far east as the CO/KS border along I-70 and as
far south as the Sangre De Cristo. Moderate Impacts are denoted
from the Laramie Range and Medicine Bow on south along the Front
Range, with some Major Impacts (considerable disruptions;
widespread closures and potential infrastructure impacts such as
power outages and tree damage) are present in the higher elevations
of these ranges, including Rocky Mountains NP. The heavy/wet nature
of the snowfall on trees fully in bloom and on power lines could
result in tree damage and power outages.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Mullinax





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FOUS11 KWBC 050849
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
449 AM EDT Tue May 5 2026

Valid 12Z Tue May 05 2026 - 12Z Fri May 08 2026

...Central/Southern Rockies and Adjacent High Plains...
Days 1-2...

Confidence continues to increase for impactful snow through the
Denver Metro in addition to CO Rockies.

A post-frontal low level convergence zone near the WY/CO border
merely drifts south through tonight before picking up some
southward speed Wednesday with the passage of a southern stream
shortwave trough currently over SoCal and a northern stream
reinforcing trough. A tight baroclinic zone through this low-level
boundary shifts south over CO and banks on the lee-side of the
Front Range today. This brings snow down to the I-25 corridor
tonight. Precip intensity increases today as left exit dynamics
strengthen from a SWly jet over NM to the central Plains and
upslope easterly flow becomes more pronounced as high pressure
builds down the Plains in the wake of the cold front.

Snow levels reach 6000ft late this afternoon from the Palmer
Divide and north before dropping below a mile high during the
evening hours. Moderate precip rates occur late tonight through
Wednesday morning from Denver through the Front Range with quick
bursts of wet snow. The focus for the snow will shift to the
Sangre De Cristo and San Juans Wednesday afternoon as snowfall
rates gradually diminish north of the Palmer Divide. Snow rates
quickly drop off Wednesday evening as the northern stream shortwave
trough pushes onto the central Plains.

Day 1 snow probs for additional >6" are 50-80% for the Wind River,
Bighorns, Laramie, and Medicine Bow Mtns in WY. Day 1.5 snow probs
for >6" are 40-70% from Cheyenne down I-25 through the greater
Denver metro and on the Palmer Divide. Meanwhile, probs for >12"
are >80% for the Front Range and Park Range. Day 2 snow probs for

6" are 50-80% for the Sangre de Cristos/San Juans and 40-70% for

the Raton Mesa.

This winter storm will produce much needed precip in the drought-
stricken Central Rockies and High Plains. However, unlike last
week's event which had less snowfall and was confined to the higher
elevations, this event is more significant and will have notable
impacts. The latest WSSI highlights widespread Moderate Impacts
for the I-25 corridor from Cheyenne through Denver and the Palmer
Divide and Major Impacts for the Front Range including Rocky
Mountain NP. The heavy/wet nature of the snow on trees fully
leafed out/in bloom and on power lines could result in tree damage
and power outages.


The probability for significant icing over one-tenth of an inch is
less than 10 percent across the CONUS.


Jackson



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FOUS11 KWBC 051838
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
238 PM EDT Tue May 5 2026

Valid 00Z Wed May 06 2026 - 00Z Sat May 09 2026

...Central Rockies and High Plains...
Day 1...

...Significant late season snowstorm continues for the Rockies and
Denver Metro through Wednesday evening...

A secondary cold front initially near the WY/CO border will bank
up against the lee side of the Front Range as it presses southward
through the CO High Plains tonight into Wednesday. In the wake of
the front, strengthening low-level upslope east to northeasterly
flow combined with favorable jet dynamics aloft will support
intensifying precip across the CO Rockies, the Denver Metro, and
the I-25 corridor this evening into the overnight hours. Marginal
surface temperatures early on may result in pockets of mixed rain
and snow along with heavier bursts of all snow dependent on precip
rate; however, post-frontal cold advection will drop temperatures
near to below freezing area wide by Wednesday morning, changing any
lingering rain/snow to all snow as snow levels crash to between
4500 and 5000ft. Moderate to heavy snow continues through Wednesday
morning from Cheyenne to Denver through the Front Range as forcing
for ascent maximizes within a fairly deep DGZ. Forcing sags
southward Wednesday afternoon, shifting the focus for moderate to
heavy snow to the Sangre De Cristos and San Juans as snowfall rates
gradually diminish north of the Palmer Divide. Snow mostly
diminishes area wide by Wednesday evening with only a few lingering
showers across the Rockies of southern CO and northern NM into
Wednesday night.

The latest Day 1 WPC probabilities of additional snowfall >4" are
50-80% from Cheyenne southward to the Denver Metro and the Palmer
Divide eastward to I-70 just west of Flagler. Probabilities of >8"
are 50-90% from the Front Range and central Continental Divide
mountains southward to the San Juans and Sangre De Cristos.
Finally, probabilities of >12" are 60-90% for the high higher
elevations of the Front Range including Rocky Mountain NP.

This late season winter storm continues to bring much needed
precipitation to the Central Rockies and High Plains, providing
some relief to places facing severe to extreme drought. With that
being said, the moisture does not come without notable impacts. The
latest WSSI continues to highlight widespread Moderate impacts for
the I-25 corridor from Cheyenne through Denver and the Palmer
Divide and Major impacts for the Front Range including Rocky
Mountain NP. The heavy and wet nature of the snow on trees fully
leafed out/in bloom and on power lines could result in tree damage
and power outages. Snow-covered and icy roads will also become a
greater concern as temperatures cool, leading to increasingly
difficult travel (especially over higher mountain passes) overnight
into Wednesday morning's commute.


The probability of significant icing across the CONUS is less than
10 percent.


Miller


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FOUS11 KWBC 060804
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
404 AM EDT Wed May 6 2026

Valid 12Z Wed May 06 2026 - 12Z Sat May 09 2026

...Southern Rockies and High Plains...
Day 1...

...Significant Colorado snowstorm continues this morning before
shifting to southern Colorado this afternoon and dissipating this
evening...

A multi-faceted positively-tilted trough is over the western U.S. A
southern stream shortwave trough will cross northern New Mexico
this morning, maintaining several more hours of mainly upslope lee-
side snow banding in the cold sector well behind a cold front and
ahead of a 1022mb sfc high shifting south from eastern Montana. A
northern stream reinforcing shortwave currently entering Utah will
swing across southwest Colorado this morning and over northern New
Mexico this afternoon which forces the precip focus to southern
Colorado this afternoon before cutting off the easterly flow and
bringing a quick end to snowfall this evening.

Day 1 WPC probabilities of additional snowfall >4" after 12Z are
50-90% from the Mosquito Range through the Sangre de Cristo Range
with 30-50% probs on the Palmer Divide, Raton Mesa, and 40-80% on
the San Juans. There are 30-50% probabilities for an additional >2"
for the southern and western Denver suburbs there the upslope
banding continues through about 16Z.


The probability of significant icing across the CONUS is less than
10 percent.



Today is the last regularly scheduled day of the season for the
WPC Winter Weather Desk. Resumption for significant winter weather
will occur as needed. Routine operations resume for the WWD in
later September.



Jackson



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FOUS11 KWBC 061754
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
154 PM EDT Wed May 6 2026

Valid 00Z Thu May 07 2026 - 00Z Sun May 10 2026

...WPC Winter Weather Desk no longer routinely staffed until
late September, 2026...

Pending any significant winter weather, the WPC Winter Weather Desk
will not be staffed through the summer. The desk will resume
continuous staffing starting in the fall.

The WPC winter products will continue to be produced, however, and
all products except the heavy snow discussion (HSD) will be
available. This includes the Winter Storm Outlook (WSO), Winter
Storm Severity Index (WSSI), and Probabilistic Winter Precipitation
Forecasts (PWPF).


WPC


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