textproduct: Cheyenne

KEY MESSAGES

- A winter weather advisory will go into effect for the Sierra Madre and Snowy mountains Sunday morning for snow accumulations up to 10 inches.

- A High Wind Watch has been issued for the wind prone areas of southeast Wyoming beginning Monday evening.

- Very active long term forecast expected with multiple troughs moving through and promoting snow chances.

- Temperatures will remain very cold through mid-week, before a weak warming trend arrives Wednesday onwards.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 310 AM MST Sun Nov 30 2025

Current observations across the area show a very cold night with temperatures now around 10 below zero over portions of east central Wyoming and western Nebraska. Light surface snow pack and clear skies/light winds for much of last night has provided suitable conditions for temperatures to bottom out to near record low temperatures. Chadron destroyed their previous record of -1 yesterday, set in 1985, with a low of -9. Expect a few other record lows to be met early this morning. Further west, thick cloud cover is spreading eastward ahead of the next clipper-like system. This cloud cover has resulted in temperatures remaining in the single digits and low teens across much of southeast Wyoming...so expect temperatures to climb slowly for the rest of the morning ahead of the next fast moving clipper. The same will likely happen to western Nebraska as the cloud shield will be over Chadron and Sidney before sunrise.

Not much of a break today as models show the clipper digging southeast into Utah and eventually Colorado by this evening. Synoptic models continue to struggle with the impacts of this system and show hardly any snowfall. However, these models traditionally don't do well with overrunning/WAA aloft along arctic boundaries...which is what we're facing today and especially this evening. High res guidance (HRRR, NAMNEST) and short range ensembles show a different story, with persistent snowfall across much of southeast Wyoming beginning late this morning and continuing through this evening. Although snowfall is expected to be pretty light, high res guidance shows some moderate snow banding along I-80 as the upper level vort max gets close to the Wyoming border. Normally, this isn't too much of a concern, but ground temperatures will support snow accumulation through much of the day with forecast highs only in the low to mid 20s at best, and hardly any breaks in the cloud cover. Continued to increase POP across the area...and even extended mention of snowfall well into western Nebraska with the HRRR showing widespread light snowfall until midnight tonight. Kept the Winter Weather Advisory going for the mountains with a solid 6 to 10 inches of snow. May need to extend this Advisory into the lower elevations and I-80 Summit area today if snowfall rates are higher than models currently suggest. However, current snow accumulations are a little shy of 3 or so inches, so will keep them out of the Winter Weather Advisory for now. Further east, can't rule out snow accumulations of over 2 inches, but confidence is pretty low...so just nudged snow accumulations up slightly and extended them further east past the I-25 corridor. Remaining cold tonight with lows back into the single digits in periods of light snow and/or flurries through midnight. Expect some clearing towards sunrise Monday, so low temperatures may trend lower with any surface snowpack.

Attention then shifts to winds and possible blowing snow on Monday and Monday night. Once Sunday's clipper system moves east of the area, another disturbance will quickly dig south into the Pacific NW, Idaho, and Montana. This system will have a strengthening upper level as it moves southeast. All models show low to midlevel pressure gradients responding with increasing 700mb subsidence along the spine of the mountains. The GFS, NAM, and Canadian all show 700mb winds increasing over 60 knots by early Tuesday morning...which is a clear upward trend compared to previous model runs. In-house wind guidance shows increasing probabilities, especially near the Arlington/Elk Mountain area, with values as high as 90%. With this in mind, issued a High Wind Watch starting Monday evening for the I-80 corridor including Arlington...with the I-80 Summit and foothills and the Bordeaux area along Interstate 25 starting a few hours later at 800 PM local time. In-house wind guidance shows the potential for 70+ MPH winds at Arlington, so went more aggressive with that zone compared to the others. In addition, some surface snow pack is expected which may lead to blowing snow concerns in a few of these High Wind areas. This will depend on a few factors, including snow depth and timing of the strongest winds. Monday is expected to be warmer, with highs in the 30s and low 40s. How much this influences a light snowpack is unclear, but will add some blowing snow to the forecast for Arlington/Elk Mountain to start out. Kept the High Wind Watch valid through Tuesday evening for the Arlington area since the low level pressure gradient will struggle to weaken.

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 321 PM MST Sat Nov 29 2025

Long term remains active as we see a system bring gusty winds and precipitation chances to start the period, followed by a brief dry period alongside some warming to bring us back to near normal temperatures, but another approaching system at the end of the period will cause another potential high wind event alongside increasing precipitation chances once again.

Into Tuesday, as the trough starts to move into the region, precipitation overspreads with temperatures also cooling thanks to the passing cold front. Expect as precipitation moves in later Tuesday through Wednesday, we should be cold enough at all levels to promote snowfall, but without a strong amount of QPF, overall accumulations should be fairly light - a few inches for the mountains, and around an inch or less for lower elevation locations, with some locally heavier amounts not out of the question and windy conditions promoting blowing snow and some locally high drifts.

Temperatures on Wednesday remain widespread at our below freezing for highs, but expect a gentle warming trend thereafter with highs warming into the 30's to 40's by Friday. The region will dry out on Wednesday, but Thursday into Friday we should see a return of light to occasionally moderate mountain snow thanks to upslope flow. And on the note of our flow pattern, models continue to indicate we'll be seeing our next high wind event Friday into Saturday with the approach of our next trough, with in house guidance already peaking into the 60-80% probability range for our wind prone locations. While overall active, overall current forecasts suggest our most impactful conditions will remain the region's usual high winds as we move into the start of December.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1053 AM MST Sun Nov 30 2025

A mix of all flight categories expected as a system brings widespread snow showers to the region today through tonight. All sites are expected to have nearby snow showers if not moving directly over, though airports that are most likely to see precipitation are all WY terminals as well as KSNY. These snow showers could cause VIS and/or CIGs to drop to IFR or even LIFR status at times. Winds will also be breezy as this activity moves through, with speeds 10-25 knots expected. As we move into this evening and overnight into tomorrow, winds should lessen and precipitation should exit the region, with skies lifting and clearing as well. Winds will begin to pick back up tomorrow into the afternoon.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Watch from Monday evening through Tuesday morning for WYZ106-116-117. High Wind Watch from Monday afternoon through Tuesday evening for WYZ110. Winter Weather Advisory until 5 AM MST Monday for WYZ112-114. NE...None.