textproduct: Cheyenne

KEY MESSAGES

- Warmer and drier weather will continue through Sunday, leading to near critical fire weather conditions.

- The potential for cool temperatures and widespread precipitation continues to increase for Monday afternoon through Wednesday morning. Thunderstorms, beneficial rainfall, and accumulating snow are all possible, but the details are still uncertain.

- Drier, warmer, and windier weather returns to the area for the second half of the work week.

SHORT TERM /THROUGH MONDAY/

Issued at 350 PM MDT Sat May 2 2026

An upper level ridge is passing overhead this afternoon and moving southeast, allowing for clear skies apart from some cirrus clouds. Daytime heating will promote deep mixing of the near surface boundary layer and will drop relative humidity values into the low teens and single digits for locations east of the Laramie Range. Recent observations from the Douglas to Chadron corridor have observed frequent wind gusts up to 25-30 MPH and RH values in the low teens. With the over performing winds and humidity values expected to keep decreasing through the afternoon, we have elected to issue a red flag warning for our northern CWA fire zones through 8 PM. Elsewhere, east of the Laramie Range, infrequent wind gusts up to 25 MPH will preclude critical fire weather conditions. Conditions still remain elevated given the very dry humidity values. A weak cold front is expected to start moving into the area this evening, bringing with it slightly higher RH values and a wind shift out of the north-northeast.

Sunday appears to be slightly cooler with the passage of the weak frontal boundary and increased cloudiness from an upper level low moving over the Pacific coast. The morning starts off cool, with most places in the upper to lower 30s. The increasing mid level moisture contributed by the Pacific system will help support a few showers and thunderstorms in the afternoon hours, particularly in our northern CWA counties. The right entrance region of a 500 mbar jet streak along with the passage of a weak shortwave trough will help provide lift for these storms. MUCAPE values range from 500-700 in most high resolution guidance. An inverted-v sounding will favor high based showers and storms. With the propensity for dry air entrainment of the downdraft these showers and storms will be on the dry side. Gusty winds and lightning are possible. An isolated storm or two may develop further south from Laramie County east to Cheyenne Co., however given the even drier conditions, any measurable rainfall is unlikely. Relative humidity values are expected to be low again Sunday with widespread minimums in the low 20s down to 15%. Winds appear to be light and variable, so no critical fire conditions are anticipated, though conditions remain elevated.

Monday the Pacific system starts to make its way east into the Southwest and turn northeastward. The positively tilted trough becomes elongated as it begins to merge with the trough over Canada with the axis of the trough centered overhead. A vorticity maximum on the western periphery of the north trough will provide the majority of lift and mositure for a period of unsettled weather starting Monday afternoon. At the surface a strong cold front will be moving south out of Canada. Along and behind this front will be the focus of widespread showers and thunderstorms. PoPs are around 40-70% for a good amount of the area in the afternoon, with greater coverages in our western areas. Ahead of the cold front, and west of the Laramie Range, steep 0-3 km lapse rates and marginal EBWD may support a few strong storms capable of small hail and gusty winds.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

Issued at 350 PM MDT Sat May 2 2026

Temperatures will continue to drop through this period ahead of another vort-max dropping down from the north which should arrive Tuesday afternoon or evening. Models are now in fairly good agreement showing the closed low over the southwest getting absorbed by the parent trough Tuesday night into Wednesday morning. In terms of our outcome on the ground, we should see snow levels starting off around 9 to 10 kft Monday afternoon, but this will rapidly drop overnight and through the day Tuesday. The latest LREF has 700-mb temperatures down to -4C over Cheyenne by daybreak Tuesday, with high confidence in values between -5 and -8C during most of the daytime hours Tuesday and into Wednesday morning. This would be cold enough to rain changing to or mixing with snow for the entire area. There is still a bit of uncertainty in the timing. If most of the snow falls during the day, the snow accumulation expectations will be considerably less due to the very strong early May sun, whereas snowfall at night would be much more likely to accumulate. As a result, we won't get into too much detail on the potential snowfall amounts. The current most likely scenario would mean accumulating snow above about 5500 ft in elevation. The 12z LREF clusters have trended the highest probabilities for precipitation further south onto the Colorado side of the border. Cheyenne now has a 60-70 percent chance for greater than 0.5 inches of precipitation and Scottsbluff has a 20 to 30 percent chance. The current forecast has still been trended towards the 25th percentile as their is still variability in the storm track and previous storms fizzled out and not being able to overcome our stout dry layer near the surface. A few rain and snow showers may linger into Wednesday with temperatures remaining 10 to 15F below seasonal averages. Ridging will build back into the western CONUS for the end of the upcoming work week. We may see a period of windy conditions Wednesday night through Thursday as this transition occurs. Current probabilities for high winds in the wind prone areas are around 20 to 40%. Warm air advection will return quickly during this period as well. We should see temperatures climb back to near seasonal averages on Thursday, and then above average by Friday.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 541 PM MDT Sat May 2 2026

Clear to partly cloudy skies should allow VFR conditions at all terminals through the evening, with some lowering in ceilings possible as moisture starts streaming in from the systems to our northwest. A weak cold front will drop south over most terminals except KRWL overnight. A wind shift from the north-northeast is anticipated with this front with slightly lower ceilings to around 10 kft. A very shallow inversion is possible with this front, however winds aloft are not particularly strong. Sunday afternoon some thunderstorms are possible for KBFF, KCDR, and KAIA. These storms are scattered in nature. If one approaches the vicinity of a terminal one can expect lightning and gusty variable winds. Some high resolution models are suggesting gusts above 40 knots are possible on the advancing side of these storms highlighting a dry microburst potential.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning until 8 PM MDT this evening for WYZ417-418. NE...Red Flag Warning until 8 PM MDT this evening for NEZ434-435.