textproduct: Cheyenne

KEY MESSAGES

- Scattered rain and snow showers in Carbon and Albany counties late tonight into Tuesday morning may result in a few slick spots along the I-80 corridor and accumulating snow above about 8500 feet in elevation.

- A strong but compact system will bring a chance for rain to the High Plains, mainly Tuesday afternoon and evening.

- Warmer and drier weather returns for Wednesday and Thursday, bringing elevated to critical fire weather conditions and marginally high winds in the wind prone areas.

- A potent weather disturbance will produce windy, colder and wetter weather for Thursday night and Friday.

SHORT TERM /THROUGH THURSDAY/

Issued at 300 PM MDT Mon Apr 13 2026

Warm and dry conditions remain over the area once again today. Breezy to windy conditions are producing widespread critical fire weather conditions. Current GOES water vapor imagery shows a messy synoptic weather pattern across the western CONUS. At least three disorganized upper level lows are circulating over the area. As each of these features traverses east, we will have a complex setup heading into Tuesday. The main player will be the nearly closed low currently over southern California which will move off to the northeast over the next 24 hours, but this will get interference from another upper level low currently over the northern Rockies. Upper level moisture will increase from the southwest, supporting a few virga showers this afternoon and evening. As moisture aloft improves, these will be more likely to reach the ground especially after midnight or so. Look for rain and snow showers to spread across Carbon and Albany counties into Tuesday morning. Snow levels will start out between 6500 and 7500 feet, supporting a rain snow mix along I-80 between Cheyenne and Rawlins. Due to the pre-dawn timing, there could be some light accumulations and slick spots in these areas with daybreak Tuesday, but conditions should improve quickly with the strong April sun. The higher peaks will also benefit from much better orographic lift. Above 10,000 feet or so, probabilities for 6" or more of snow are around 50 to 65%. This could warrant a low end Winter Weather Advisory, but opted to pass on this due to the marginal totals confined only to the highest peaks. Still, travelers in the mountains should prepare for some areas of snow and slick conditions Tuesday morning. Further east, a southwest to northeast oriented low-level convergence boundary is expected to kick off elevated shower activity, but it will be harder to overcome the dry boundary layer east of the Laramie Range. Still, PoPs in the 15 to 40 percent range are present over the area. Surface winds will be all over the place on Tuesday, but speeds should be fairly light with the possible exception of the I-80 corridor between Laramie and Sidney where east to southeast winds may be gusty at times.

Heading into Tuesday afternoon, the approaching upper level low will support lee-cyclogenesis over northeast Colorado. The morning convergence boundary supporting the shower activity will get pulled into the strengthening system as it moves off to the northeast. Models show fairly potent mid level frontogenesis as this occurs, and a very narrow TROWAL developing by Tuesday evening as the system departs. The main uncertainty is where exactly this occurs. The overall system will be extremely compact, such that a difference in 50 to 100 miles in the exact location of lee cyclogenesis could mean the difference between beneficial rainfall and nothing at all for the High Plains. In addition to the synoptic forcing, a few hundred J/kg of CAPE are expected to be present, so some isolated embedded thunderstorms will be possible. The most likely scenario tomorrow evening will be a band of moderate rainfall traversing from west to east across the area, with potential for localized areas receiving over 0.25" of rainfall. There are still a few ensemble members (and the deterministic GFS) that keep the forcing for rainfall entirely south of our area, but model consensus is for this to occur somewhere likely south of a Wheatland to Chadron line. Overall confidence is pretty low in precipitation amounts and location, but there will be a high ceiling too due to the strong but narrow forcing and plentiful mid to upper level moisture. Light rain may continue after midnight, but we should be done with this system by Wednesday morning.

Ridging will rebound over the area on Wednesday into Thursday, resuming the mild and dry weather pattern that has dominated this season so far. Look for temperatures around 5 to 10 degrees above seasonal averages on Wednesday, climbing closer to 15 degrees above average for Thursday east of the Laramie Range. Expect breezy westerly flow on Wednesday, which will turn southwesterly on Thursday ahead of the next system diving into the Pacific northwest. Widespread elevated to near critical fire weather conditions will be present both days. In addition, we will need to watch for another round of marginally high winds. The wind prone areas have approximately a 30 to 40% chance for high winds on Wednesday. As the flow turns more southwest Thursday, this will decrease to around 10 to 20% for the I-80 summit and Bordeaux areas, but increase to around 50 to 60% for the Arlington and Elk Mountain areas. This may also extend a little further west than usual, perhaps into the Rawlins area. LREF median 700-mb winds are around 45 knots over Rawlins Thursday morning, which gives probabilities around 50 to 60% here as well. As is typical with southwest flow, we will also have to watch Converse county, which currently has a 30% chance for seeing high winds on Wednesday night and Thursday.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Issued at 300 PM MDT Mon Apr 13 2026

Thursday night-Friday...A progressive and sharp trough aloft and its associated cold front move from Idaho and Utah Thursday evening, to western Wyoming late Thursday night, with the cold front passing our counties Thursday night. The trough axis aloft tracks across our counties during the day on Friday. Fairly high confidence in scattered to numerous rain and snow showers spreading from west to east Thursday night, with likely to widespread snow showers Friday afternoon. Much cooler and windy on Friday with maximum temperatures in the mid 30s and 40s. Winter weather highlights may be needed for the mountains and nearby locations.

Saturday...Snow showers will gradually end from west to east early in the day, as the shortwave trough aloft moves into the northern Great Plains states. Strong low and mid level northwest flow will help produce a windy day, with possible high winds for our wind prone locations. Somewhat warmer than Friday with 700 mb temperatures near 6 Celsius.

Sunday...The flow aloft weakens as low amplitude shortwave ridging aloft develops over Wyoming, producing dry conditions and mild temperatures in the upper 50s and 60s with 700 mb temperatures near 2 Celsius.

Monday...Ridging aloft moves over our forecast area, with surface lee troughing over our eastern counties, producing a dry and mild day. 700 mb temperatures near 8 Celsius will yield maximum temperatures in the mid 60s west of I-25, with 70s east of I-25.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1055 PM MDT Mon Apr 13 2026

A Pacific disturbance is forecast to push eastward along the Wyoming/Colorado border into late Tuesday afternoon. Scattered to numerous showers, some high elevation snow, and even a few thunderstorms are possible along the Interstate 80 corridor and close to the Colorado border 09z through 00z Wednesday.

HAZARDS/WEATHER TRENDS: Low confidence Aviation forecast over the next 18 hours, particularly over the southeast Wyoming terminals and KSNY. Expect VFR conditions to prevail at KCDR, KBFF, and KAIA with maybe a few light showers Tuesday afternoon. Further south, limited confidence in precip coverage and forecast VIS over KRWL and KLAR due to some snowfall or rain/snow mix. Even less confidence for KCYS and KSNY with model solutions showing poor run to run consistency for these two locations. Fow now, will keep the best chance for IFR conditions and brief periods of snow to KLAR even though probabilities for IFR are less than 15%. Added a mention of TSRA for KSNY with high res guidance in somewhat good agreement with thunderstorm activity confined to that region late Tuesday afternoon and Tuesday evening. Any MVFR or IFR conditions are expected to be brief and/or rapidly fluctuate. Expect clearing skies at all terminals after 03z Wednesday once the disturbance ejects eastward into the Great Plains.

CYS WATCHES/WARNINGS/ADVISORIES

WY...None. NE...None.