textproduct: Cheyenne

KEY MESSAGES

- Critical Fire Weather conditions expected again Monday as humidities dive into the single digit values.

- Pattern change alongside a chance at some precipitation including storms and snow expected mid through end-week timeframe.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 244 AM MDT Mon Apr 20 2026

Benign weather is expected over the next few days as upper-level ridging moves into the Rockies. Temperatures will continue warming on both Monday and Tuesday as the ridge axis pushes eastward into the CWA. 700 mb temperatures will climb to about +8C on Monday, leading to high temperatures in the 70s and 80s across the forecast area. Highs are expected to be even warmer on Tuesday as the ridge axis sits over the CWA. 700 mb temperatures will reach +10C, leading to highs in the 70s to upper 80s, which is roughly 20 degrees above average and approaching record highs. The ridge will also ensure that mostly sunny skies dominate the area, with minimal precipitation chances anticipated. As a result, conditions over the next few days are expected to extremely dry. With dry desert air being advected into the region, relative humidity values will fall into the single digits on both days. The extremely low relative humidity poses fire weather concerns, especially on Monday when winds are bit more breezy as a weak disturbance passes to the north. Red Flag Warnings are currently in effect through Monday for areas east of the Laramie Range. Overnight humidity recoveries are also expected to be poor Monday nights. Although precipitation chances are expected to be minimal, cannot rule out some gusty virga showers late Tuesday afternoon and evening. Hi-Res guidance does show some weak convection developing over southeast Wyoming ahead of a major incoming trough. Model soundings show strong inverted-V profiles meaning extremely dry low-levels. Over 1000 J/kg of DCAPE is also likely, leading to the potential for severe wind gusts in these virga showers.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Issued at 255 PM MDT Sun Apr 19 2026

The main stories on Wednesday are likely to be the high winds and low RH values for Wyoming, and severe thunderstorm potential for the Nebraska Panhandle. The upper level system over the Pacific Northwest will shove the ridge we've been dealing with for the last few days out to the east. Within the southwesterly flow we can expect increasing cloud coverage, starting first west and spreading east. While the ridge begins departing our area, it will still influence our temperatures and humidity. Temperatures are likely to reach the mid 70s to mid 80s over the High Plains and mid 60s over the interior basins. Ensemble models are still split on how deep the upper level low will be Wednesday. Euro and Canadian ensemble members are leaning towards a weaker system. GEFS members are deeper. This may have some implications on the magnitude of our winds and precip probabilities. For example the deterministic model runs of the ECMWF and GFS have differing central pressures, of the expected developing surface cyclone to our north, of 991 mb and 987 mb respectively. The surface wind fields of the differing strength systems are readily apparent with more widespread and stronger winds in the GFS solution. This is important to take into consideration when talking about our ML models that predict wind probabilities as these do take GFS grids as input. This model is predicting high wind criteria being met at many of our wind prone locations. The Arlington area has a 80% chance of reaching high wind criteria, Cheyenne 55%, and Bordeaux a 85%, just to list a few outputs. Local knowledge tends to favor the GFS as having a better handle on winds for the area. It should not surprise anyone if high wind products are issued should the stronger solutions look to verify. Adjusting our attention east to the Nebraska Panhandle, in the afternoon a dryline will take shape and be associated with the development of the low to our north. ML severe weather models are running more aggressive compared to yesterday in their probabilities of severe thunderstorm development along this dryline and points east of the CWA. GFS soundings are depicting a deep mixing layer and inverted-v profile that may support severe wind gusts. The bulk wind shear is just enough to possibly support rotating updrafts and increase the hail potential. How far west this dryline ultimately positions itself and where it mixes east during the afternoon and evening will determine if storms mature within our area. The storm coverage looks to be low at this time. Finally lets talk about the fire potential as this does seem to be the biggest concern for Wednesday. As mentioned, high winds are of higher confidence and relative humidity values are likely to bottom out in the low teens across the majority of the CWA. Therefore red flag conditions are plausible. Additionally, with the introduction of thunderstorms in the Nebraska Panhandle, dry lightning and variable surface winds induced by nearby downdrafts can further complicate any fire behavior.

Winds increase overnight Wednesday as the surface low departs to the northeast. Aloft we are still at the base of an upper level trough, which should increase PoPs, particularly over the mountains and northern poritons of the CWA. A Pacific cold front should move in from the west and brings our temperatures down slightly and increase moisture a little. Precip accumulations are expected to remain low. Some remaining elevated fire weather conditions may persist during the afternoon in the plains region as humidity values stay in the 20s.

Going into the overnight hours Thursday precip chances continue to increase, particularly over the mountains. An arctic cold front should make its way through our area sometime around midnight. This front should finally bring temperatures to near average Friday. Humidities during the day still appear to be on the lower side. Regardless, weaker winds and lower temperatures are likely to dampen fire potential. Saturday and Sunday look to be much the same as Friday weather wise. There is a good chance the base of the trough remains parked above the area all weekend, keeping it seasonable cool, cloudy, and perhaps showery as well.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 520 AM MDT Mon Apr 20 2026

Upper level ridge axis will move east over the Front Range during the day. Generally clear skies are expected with minimal aviation impacts. VFR conditions will continue over the area. Typical diurnal winds expected for all terminals with westerly winds becoming breezy after 16z Monday.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning until 8 PM MDT this evening for WYZ417-418- 430>433. NE...Red Flag Warning until 8 PM MDT this evening for NEZ434>437.