FOUS11 KWBC 270720
QPFHSD

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

Valid 12Z Mon Apr 27 2026 - 12Z Thu Apr 30 2026

...Great Basin, Central/Southern Rockies, & Northern Plains... Days 1-2...

Two shortwave troughs; one heading for the Great Basin and another
over the Northern Rockies, are responsible for the periods of snow
enveloping the higher terrain of the Intermountain West today and
into early Tuesday. The heaviest snowfall (rates between 1-1.5hr
possible) are most likely to unfold along the higher terrain of
the Wasatch, Uinta, and Absaroka through tonight. Snow levels will
generally hover around 7,000ft in UT/NV, around 6,000ft in the
Northern Rockies, and t/above 8,000ft in the CO/WY Rockies. As the
500mb trough over the Great Basin reaches the Central Rockies
Monday night, enhanced vertical ascent aloft will work in tandem
with a surface high building in from the north to foster upslope-
enhanced snowfall over Laramie Range in WY on south into the Park
and Front Ranges of CO. Only light snow will linger over the remote
reaches of the Central and Northern Rockies on Tuesday as the
shortwave troughs exit to the north and east.

WPC probabilities show high chances (>70%) for additional snowfall
totals >4" in the Uinta, Absaroka of southern MT, the CO
Park/Front Ranges, and WY Laramie Range. Snowfall is welcomed
throughout these mountain ranges given the Rockies anywhere from
class 2 (severe) to class 4 (exceptional) drought condition.

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

Mullinax
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

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

$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

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
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

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
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

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
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)