textproduct: Cheyenne

KEY MESSAGES

- Near to record warmth expected Wednesday under high pressure aloft.

- Critical fire conditions possible again on Thursday and Friday alongside strong winds and dry conditions. - Next chance for precipitation returns during the weekend alongside cooler conditions.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 225 AM MDT Tue May 12 2026

Surface observations early this morning show the leading edge of the cold front near the Interstate 80 corridor with westerly winds continuing at Cheyenne and south of Kimball and Sidney, with north to northeast winds north of Interstate 80 across most of the high plains. This front is pretty weak and shallow, so even cloud cover has been limited with little return from the KCYS radar so far. Expect this to continue this morning as the front will stall near the Laramie Range and dissipate by this evening. Although high temperatures will be around 10 to 15 degrees cooler compared to Monday, it will still be around 10 degrees above average for mid May. Not as cool tonight as one would expect after a cold frontal passage, mainly since all models show quick low to midlevel WAA as another ridge axis builds across the Rocky Mountain Region. This will keep low temperatures above average for this time of the year into early Wednesday morning.

Upper level ridge axis rebuilds over the Front Range for Wednesday with 700mb temperatures ranging from 10c to 15c, which translates to surface highs in the 80s across the whole forecast area and low 90s below elevations of 4500 feet. So another pleasant spring day is expected. Models are now showing a bit more convective activity in the afternoon, mainly along and west of the Interstate 25 corridor. This is in response to terrain-influenced convergence axis along the Laramie Range and along the spine of the Rocky Mountains extending into the Snowy Range. Surface winds will be out of the southeast across the high plains, but more out of the southwest across Carbon and Albany counties during the day. Some low level moisture will be present with dewpoints near 40f. In addition, models do show a weak midlevel shortwave moving into the area by the late afternoon hours. Confident enough to introduce a slight chance of thunderstorms along and just east of the Laramie Range later Wednesday afternoon. Convection will struggle against the intensity of the upper level ridge, but the midlevel shortwave should be enough to justify isolated coverage.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 120 AM MDT Tue May 12 2026

Fairly quiet end to the week on the backside of a departing upper- level trough Thursday. Southwesterly flow will slowly turn northwesterly aloft then back westerly throughout the day Thursday as the trough moves out, leading to clearing skies throughout the day. The 700mb low will remain in southern Canada throughout the day, but height gradients will remain strong as a 50 to 55kt, westerly 700mb jet develops across the Laramie Range Thursday morning then weakens to around 45kts for the remainder of the afternoon and evening hours. With strong westerly flow at 700mb, strong westerly flow is anticipated near the surface, especially as a 5mb surface pressure gradient develops across Carbon County with increasing gradients along and east of the Laramie Range. In-house random forest guidance suggests increasing probability for a lower- end high wind event setting up across much of the area Thursday, with 50% chance at Arlington and Rawlins, as well as a 40% chance at Bordeaux. One drawback is that the 700mb flow will not be that strong for very long, with the likely peak period of 700mb jet strength between about 12Z and 18Z Thursday. During this time, downward omega values are modest to strong, for a May event that is, with decent support between 800 and 700mb. Confidence is not there at this time to warrant a High Wind Watch, but Thursday morning and afternoon will be a time to pay attention to over the next several days, especially as hires model guidance becomes available.

In addition to the potential for high winds Thursday, downsloping along the Laramie Range will lead to afternoon minimum humidity values dropping well below the 15% criteria for Red Flag Warnings. single digit humidity values will be possible Thursday afternoon east of the Laramie Range, with values west of the Laramie Range between 10 and 15%. With the recent green-up across the region from the snow and rain showers, fuels remain unfavorable for burning across southeast Wyoming. However, fuels remain dry and ready to burn across western Nebraska. Fire Weather headlines may be needed for Thursday in the coming days, especially with overnight recoveries Thursday into Friday likely only around 30 to 40%, as well as the very gusty conditions anticipated Thursday afternoon. With afternoon temperatures reaching the upper-70s to mid-80s east of the Laramie Range, favorable fire spread conditions are anticipated to develop across western Nebraska by the afternoon.

Friday onwards will be largely dominated by upper-level zonal flow across much of the region. Temperatures will be quite warm Friday and Saturday as 700mb temperatures increase above about 7 to 10C each afternoon. Highs on Friday are anticipated to be in the low-70s to mid-80s, with Saturday being slightly warmer in the mid-70s to low-90s. Afternoon minimum humidity values look to remain quite low Friday and Saturday, likely between 10 to 15% each day. Luckily, winds will be on the lighter side across western Nebraska, where fuels are ready to burn, and breezier across southeast Wyoming, where green-up has decreased fire spread potential. That being said, hot and dry conditions may still favor easier fire starts, though rapid fire spread is not anticipated at this time. Instability will start increasing Saturday afternoon with the continued, hot pattern, as well as a cold front pushing through the area. An isolated thunderstorm or two will be possible Saturday, especially across western Nebraska, as is common as we move into the Spring and Summer months.

The next potentially system looks to arrive Sunday into Monday as an upper-level trough deepens over the western CONUS. There is significant disagreement in long range models at this time, as far as this system is concerned. The GFS suggests a strong, positively tilted system slowly moving across the Intermountain West Sunday through Tuesday, whereas the ECMWF suggests a quicker moving, shortwave trough moving through Sunday with a secondary shortwave trough moving through Monday into Tuesday. Both models still suggest increasing precipitation chances to end the weekend and to start the work week, but exact details and timing are highly uncertain at this time. However, with the warmer weather and 700mb temperature progged to remain right around the -3 to 0C range, primarily rain is anticipated with this system, whether that be in two waves or one, longer lasting wave. Any precipitation that is received will be quite welcomed, especially after several days of hot temperatures and little to no precipitation.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1145 PM MDT Mon May 11 2026

A weak shallow cold front will push south into the Interstate 80 corridor and into Colorado over the next few hours with winds shifting into the north. Little to no precipitation is expected with some midlevel cloudiness.

HAZARDS/WEATHER TRENDS: VFR conditions will persist over the next 24 hours with winds shifting into the north or northwest. Winds should be relatively light for most terminals, with northwest winds gusting up to 25 knots for KRWL and KLAR this afternoon.

CYS WATCHES/WARNINGS/ADVISORIES

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