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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