textproduct: Cheyenne

KEY MESSAGES

- Warming trend expected to continue through early this week with strong winds returning to southeast Wyoming late this evening through Thursday. High Wind Watches and Warning are in effect for the wind prone areas starting this evening.

- A more widespread strong wind event is possible across most of southeast Wyoming on Wednesday.

- Next chance for precipitation on Wednesday with periods of snow and rain possible.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 240 AM MST Mon Dec 15 2025

Quiet and relatively mild weather early this morning with current temperatures in the 40s and 50s over most of southeast Wyoming. Some of the higher valleys show temperatures in the 20s, but overall a pretty mild morning across the area. The coldest area is the western Nebraska panhandle which has temps as low as 17 degrees. Expect these lower temperatures to increase somewhat as we head towards sunrise with some warm air advection. Such mild temperatures for mid December are due to the large area of high pressure aloft to the south, resulting in a thermal ridge over the Front Range and 700mb temperatures as high as 8c to 10c.

All models in pretty good agreement today and Tuesday. Other than a return to windy conditions on Tuesday, mild weather is expected to continue over the whole area through Tuesday evening. Afternoon highs Monday will be similar to Sunday, with readings well into the 60s for many places, and low to mid 50s for Rawlins, Saratoga, and Laramie...which is still 20 to 25 degrees above average. Expect another round of record high temperatures for southeast Wyoming and a few might drop for western Nebraska as well. Tuesday will be a few degrees cooler compared to Monday, mainly because of increasing cloud cover and a weak low to midlevel cool front moving across the region. Otherwise, no precipitation is expected through Tuesday night.

Primary forecast concern will be strong winds developing over the wind prone areas as early as late this afternoon. Models and in-house wind guidance continues to show probability of strong winds (40+ mph sustained/58+ mph gusts) above 75% for several wind prone areas along I-80. Expect the low to midlevel pressure gradient along the spine of the mountains to increase in response to the next Pacific system moving into Montana and northern Wyoming over the next 24 to 30 hours. Although 700mb winds are not quite as strong as last night, they are still over 50 to 55 knots for the duration of the event. GFS and NAM show plenty of 700mb subsidence tonight across the wind prone areas...peaking between 600 am and noon Tuesday, with an even larger signature late Tuesday and Wednesday. With winds early this morning already gusting between 40 to 45 MPH across the wind prone areas with meager pressure gradients and forcing, decided to issue a High Wind Warning for the Arlington/Elk Mountain are starting this evening at 5 PM, and issued a High Wind Watch for the central and southern Laramie Range including Bordeaux and the I-80 Summit/foothills. Went with a Warning for Arlington since this event might start at any time over the next 12 hours, but decided on a Watch for the Laramie Range since the onset of winds may be delayed by 6 to 12 hours. Kept the High Wind headlines going through most of Tuesday. There is a bit of a break between this event and the stronger event on Wednesday based on current model trends, so will message each event separately. For Tuesday, some of these winds will mix down to the surface for the lower elevations of southeast Wyoming. Will need to watch this trend since some ensemble guidance is showing wind gusts nearing 55 to 60 MPH for Laramie, Cheyenne, and eastern Platte County/just north of Wheatland. Increased winds a bit for windy conditions, but kept gusts shy of High Wind criteria.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Issued at 1258 PM MST Sun Dec 14 2025

With a generally low amplitude upper air pattern through the next week there is good synoptic agreement upon how the pattern unfolds. Beyond the Monday night clipper to the north along the international border will be a stronger wave come Wednesday that dives a bit further south into the northern tier US states with subtle timing and strength differences among global ensembles. The GEFS and Euro ensembles show good agreement on track and timing of the wave but disagree slightly on the amplitude. Whereas the GEFS and Canadian ensembles agree better on the amplitude of the wave as it passes to our north but show subtle timing differences with the GEFS being slightly slower in its progression. Now what do these differences mean in terms of impacts for the forecast area? Probably just differences in when the wind shuts off after it begins.

Looking at Wed AM through Thur AM we see 700mb flow ticks up over 60kts with some members showing as high as 70kts or more (low confidence on that). This will likely bring more widespread high winds to the region with available guidance showing this to be a more widespread event likely bleeding outside the wind prones and into the adjacent high plains. This Wednesday event looks to be a quick hitter and not long lasting thankfully (<24 hours). The pressure gradient then looks to reverse for Thursday (once winds die down on which timing is still low confidence) shutting off the wind machine for a short time before another surge in winds aloft brings flow equal to if not slightly stronger than the Wednesday event. This would begin late Thursday lasting well into Friday and possibly early Saturday. Flow then looks to turn more zonal with lesser chances for shortwave activity to bring impactful winds the region.

Along with the winds should come some light shots of moisture Wed/Thur and again next weekend. This would be most impactful for the high terrain (above 8000ft) where a few inches of snow would be expected though can't rule out a few hundredths of rain or a dusting of snow in the low elevations. Looking at temps quickly we are quite a bit above average (37-42F along east of I25) with highs likely to reach well into the 50s for areas below 7000ft Wednesday and then Friday through the weekend. Thursday will be slightly cooler in the 40s behind a cold front. Low to mid 60s even appear probable Wednesday and Friday with high temperature records very much in danger for most locations on Friday.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 450 AM MST Mon Dec 15 2025

Quiet conditions with relatively light winds and clear skies continue through Monday. Winds are forecast to increase over the southeast Wyoming terminals Monday night and continue through Tuesday.

HAZARDS/WEATHER TRENDS: VFR conditions expected with light and variable winds overnight through sunrise Monday. Winds will become breezy over the southeast Wyoming terminals after 18z with west winds gusting to 25 to 30 knots this afternoon.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Watch from this evening through Tuesday morning for WYZ106. High Wind Warning from 5 PM this afternoon to 3 PM MST Tuesday for WYZ110. High Wind Watch from this evening through Tuesday afternoon for WYZ116-117. NE...None.