textproduct: Cheyenne

KEY MESSAGES

- A very strong cold front will sweep through the area between the late afternoon and evening hours today, bringing rapidly dropping temperatures and an abrupt wind shift.

- Snow squalls and a flash freeze will be possible this evening, primarily in Carbon and Converse counties.

- Widespread snowfall is expected this evening through Friday, though exact accumulations remain uncertain.

- Winter-like temperatures in the teens to low 20s are expected by Saturday morning, creating a risk for outdoor irrigation and sensitive vegetation that has emerged from winter dormancy early.

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 311 PM MDT Thu Apr 16 2026

Lower level water vapor shows the cold front slowly working its way southeast past the tetons and bighorns. Surface observations put the front just past Gillette and into the Black hills area and picturing a diagonal line it runs Northwest of Casper and runs east into the Wind River Reservation going of where the northerly winds and higher RH values are. The strongest moisture plume also looks disconnected and behind the actual front itself. So the heavier snowfall may be a little later than what Hi-res Guidance is suggesting. However, Hi- res guidance shows a stronger pressure gradient along the front as well as some stronger Isentropic lift as well. Guidance also agrees that there will some strong frontogenesis and multiple lobes of vorticity both along and behind the front. This combination of mesoscale and synoptic forcing should produce some light brief rain as it rapidly lifts what marginal moisture we have in our area up into the air. It should be enough to lightly wet ground and roadways as the front moves southeast. The cold air behind the front should rapidly flash freeze any wet pavement creating a slick icy surface. This should also transition any light rain showers into snow showers. Snow squalls are a possibility as the Northerly winds look to remain elevated between 25 to 35 mph. So if snow showers do develop, some greater reductions to visibilities will occur with possible whiteout conditions. By Friday morning the front should be pushing through into Colorado. By then the main trough will be pushing through increasing the synoptic forcing across the forecast area. The main bulk of the snow will come from the trough passage. Snow accumulations look to be between 4-6 inches near the mountains with 1-3 inches in the valleys in Carbon and Southern Albany county. Along the I-25 corridor looks to be 1-3 inches with the higher amounts closer to the higher elevations. In the "far eastern" counties including the eastern portion of Laramie county and the Nebraska Panhandle. Snow accumulations look to be between a Trace and 1 inch. Due to the ground temperatures being pretty warm initially, snow accumulations may be less due to snow melting on the ground and taking a minute to cool down and starting to accumulate. Snowfall looks to end Friday night. 700mb temperatures drop down to -13 to -15c behind the trough dropping our high temperatures into the 30's in Southeast Wyoming and possibly 40's in the Nebraska Panhandle for Friday's high temperatures. The cold airmass with reside over the Intermountain West until about midday Saturday. Friday Night will be the coldest of the week as widespread teens and low twenties across the forecast area. Saturday, An upper level ridge will start to push into the Intermountain West. Temperatures look to rebound into the 40's and 50's on Saturday thanks to the combination of a "summer- like" sun and the cold airmass pushing east. THe intermountain west will still be in a northerly flow so temperatures will be slow to rebound, but temperatures Saturday night looks to be in the mid twenties with a couple areas possibly reaching the low thirties.

LONG TERM /SUNDAY THROUGH THURSDAY/

Issued at 311 PM MDT Thu Apr 16 2026

The long term period will begin under a high amplitude mid-level ridge resulting in dry conditions with above-average temperatures, translating to forecast highs in the mid to upper 60s east of the Laramie Range with 50s further west. Longwave ridging will remain in place over Southeastern Wyoming and Western Nebraska heading into Monday, resulting in median 700 mb temperatures exceeding the 95th percentile for our entire area per LREF guidance. While this won't translate to record-breaking high temperatures at the surface (76 degrees is the record for Cheyenne, recorded back in 1989), we will continue to see anomalously warm temperatures of 15-20 degrees above climatology. Mean 700 mb flow looks to be rather relaxed at around 20 knots, so high wind highlights aren't anticipated at this time. This is supported by in-house random forest guidance which has the wind-prone areas at < 20% probabilities of meeting high wind criteria. However with ensemble guidance showing 75th percentile wind gusts exceeding 20 mph and RH values of 15-20%, fire weather highlights may be needed as we get closer to Monday. Any beneficial moisture we can get from the system on Friday and earlier in the weekend would help mitigate these concerns.

Tuesday, the ridge axis will be situated over the eastern half of Wyoming with 500 mb heights exceeding the 90th percentile relative to climatology. Unsurprisingly, this will be accompanied by another day of high temperatures around 20 degrees above-average. In fact, some of our Nebraska counties will likely exceed 80 degrees. On Wednesday the ridge axis will shift east of Wyoming and Western Nebraska ahead of a closed 500 mb low, placing us in broad SW mid- level flow. While large-scale forcing for ascent appears rather weak, ensemble guidance is hinting at a narrow band of enhanced 700 mb frontogenesis east of the Laramie Range. This mesoscale forcing for ascent will become more clear and quantifiable in future forecasts, however in combination with PWAT anomalies around the 90th percentile, a chance of showers and perhaps a few thunderstorms seems appropriate at this time, most likely confined to the higher terrain. Thursday will continue to be unsettled, however temperatures look to remain above-average as we remain in a SW flow regime.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1135 AM MDT Thu Apr 16 2026

A progressive weather disturbance aloft will move across the terminals on Friday, while its associated cold front sweeps from west to east across the terminals this evening.

Wyoming TAFS...Moderate confidence in ceilings and visibilities lowering to IFR this evening at Rawlins due to a cold front, then ceilings improving to VFR briefly late tonight before lowering to MVFR after 12Z Friday. The pressure gradient will support winds gusting to 44 knots through this afternoon, and to 30 knots tonight and Friday morning.

For Laramie and Cheyenne, moderate confidence in ceilings lowering tonight to low VFR, with light snow and MVFR ceilings after 12Z due to a passing cold front and weather disturbance. Gradients support winds gusting to 40 knots this afternoon, then 22 to 32 knots starting tonight.

Nebraska TAFS...Moderate confidence in ceilings lowering to low VFR tonight with the passing of a cold front, with a chance of showers at Chadron and Alliance this evening, and occasional light rain reducing visibilities to 6 miles from 06Z to 12Z. Light snow and MVFR ceilings will continue at Scottsbluff Friday morning after 12Z. Winds will gust to 35 knots due to the low level pressure gradient.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning until 8 PM MDT this evening for WYZ417>419- 430>433. Winter Weather Advisory until noon MDT Friday for WYZ101. Winter Weather Advisory until 3 PM MDT Friday for WYZ103>105- 109>111-113. High Wind Warning until 9 PM MDT this evening for WYZ104-109- 110-113. NE...Red Flag Warning until 8 PM MDT this evening for NEZ434>437.