textproduct: Cheyenne

KEY MESSAGES

- Dry conditions and above average temperatures will continue through the work week.

- Fire weather will be a concern, alongside a chance at record high temperatures both today and Tuesday.

- A pattern change is increasingly likely beginning around Sunday into early next week, but the details remain uncertain.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 1108 AM MDT Mon Oct 5 2026

A toasty day is in store for us across SE Wyoming and the Nebraska Panhandle, as record-breaking warmth is expected across our area underneath broad longwave ridging over the western half of the country. Although the ridge dampens throughout the day, 700 mb temperatures are progged to exceed the 99th percentile relative to climatology resulting in high temperatures expected to reach the mid to upper 80s east of the I-25 corridor, with a few 90 degree readings possible across Western Nebraska. As it stands, HREF guidance has a 50th percentile high temperature of 83F in Cheyenne, which would break the previous record high of 82F set way back in 1947. While stations such as Scottsbluff and Chadron are likely to fall just short of record territory (daily records are in the low to mid 90s), these locations are still expected to see high temperatures averaging 15-20 degrees above climatology.

Aside from the heat, the main concern today will be fire weather conditions, as a lee trough establishes itself across the region, which will result in an uptick in gradient flow and our winds. As minimum RH values are anticipated to range from 10-15% east of the Laramie Range combined with peak gusts of 20-30 mph and plenty of dry fuels, outdoor burning is not recommended today, hence the issuance of a Red Flag Warning until 6 PM today. Further, rather poor overnight recoveries of only 35-40% are expected, which may continue any fire weather concerns into tomorrow as we remain in an anomalously hot and dry pattern.

The longwave ridge bringing us these unseasonably warm temperatures will continue to weaken into tomorrow, however with NAEFS guidance showing 500 mb geopotential height still exceeding the 90th percentile, well above-average high temperatures are expected again. Regardless of whether or not more temperature records are broken tomorrow (Laramie and Rawlins are forecast to exceed the daily record, with Cheyenne tying), we can still expect to see temperatures range from 15 to 20 degrees above average, with low to mid 80s east of the I-25 corridor and mid 70s to the west. Median RH values tomorrow afternoon are in the 15-20% range, however winds will be weaker than today resulting in a more marginal fire weather setup, hence allowing the Red Flag Warning to expire this evening with the possibility of another issuance for tomorrow during the day depending on trends this afternoon and evening. Tomorrow night will remain dry, though slightly cooler given the decrease in winds allowing for more effective radiative cooling. It may seem hard to believe, but our average overnight low in Cheyenne tomorrow is in the upper 30s, and we likely won't dip below 45F. The trend of above- average temperatures will continue through the rest of the work week.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Issued at 205 PM MDT Mon Oct 5 2026

High confidence in warm and dry weather continues through Saturday, but a major pattern change is increasingly likely beginning around Sunday.

Broad ridging will continue to dominate the western US through the end of the week. Ensembles are in pretty good agreement showing the strength of the ridge moderating just slightly on Wednesday and Thursday, so forecast highs will be just a few degrees cooler than today and tomorrow. Temperatures will be closest to records again at Laramie and Rawlins, as the core of the ridge will remain to our west. While humidity will remain low and lead to elevated fire weather conditions, winds are expected to remain light through this period. Therefore, critical fire weather conditions are unlikely. The ridge will start to amplify again on Friday into Saturday as its axis shifts rapidly eastward towards the central CONUS. 700-mb temperatures will remain around the climatological 90th percentile for this period. With the ridge moving east, flow aloft will turn more to the southwest, opening the door to increased wind speeds especially in Carbon, Albany, and Converse counties. While high winds are unlikely (10-20% chance) this may increase fire weather concerns for Friday and Saturday. In addition, a few ensemble members show some disorganized vorticity meandering through our area under the ridge during this period. Combined with the southwest flow increasing mid to upper level moisture, we may see isolated high- based showers returning to the forecast by the end of the week. Current chances for measurable precipitation remain slim.

Major changes are increasingly likely beginning around Sunday. While confidence is high that something will change, there is low confidence in what the new weather pattern will look like. Ensembles are unanimously showing some type of powerful Pacific trough approaching the area Sunday or Monday, but are in very poor agreement on exactly how this moves through the area. The LREF suite is split nearly 50-50 into two clusters. In one cluster, the Pacific trough moves through more quickly, and as an open wave. This would lead to a dramatic cool down on Sunday or Monday with higher chances for widespread freezing temperatures. Overall QPF expectations are lower in this scenario (widespread 0.1 to 0.4"), but the chance for snow falling in more populated areas would be higher. The other cluster of ensembles depicts the upper level low diving further south and closing off over the western US. The storm moves through much more slowly, leading to significantly warmer temperatures Sunday and Monday and a delayed cool down after the end of the operational forecast period. In this scenario, overall QPF expectations look considerably higher (widespread 0.4 to 0.8", but the chance for snow would be lower due to warmer temperatures when precipitation is falling. One other interesting tidbit is that ECMWF AIFS and GEFS AI members tend to strongly prefer the faster, drier, and colder former scenario. This will be an interesting event to watch for the performance of these relatively new guidance tools.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1229 PM MDT Mon Oct 5 2026

VFR conditions are expected for the forecast period. Occasional wind gusts between 20 and 30 knots can be expected at Wyoming terminals through the late afternoon hours, but winds will die down after sundown. Expect lighter and occasionally variable winds overnight.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning until 6 PM MDT this evening for WYZ418>422- 427-430-432. NE...None.