textproduct: Cheyenne

KEY MESSAGES

- Mostly dry and warmer weather will prevail for Sunday through Wednesday, with thunderstorms possibly returning late in the week.

- Near Critical fire weather conditions possible over east central Wyoming and the northern Nebraska Panhandle Monday afternoon.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 250 AM MDT Sun May 10 2026

Current Satellite loop and KCYS radar imagery shows the upper level trough beginning to exit the region with clearing skies north of Interstate 80. A band of showers with embedded thunder has developed along the I-80 corridor from Cheyenne to Sidney, with scattered showers expected to continue over the next 4 hours to around sunrise. This activity should move south and dissipate shortly after sunrise with sunny skies and dry weather expected through Sunday afternoon. After a chilly morning this morning, the cooler air aloft and near the surface will quickly move east of the area today as 700mb temperatures climb above 5c. High temperatures in the 60s to low 70s are expected this afternoon, warmest over eastern Wyoming and the northern Nebraska Panhandle.

Even warmer temperatures are forecast to start of the work-week as a broad ridge axis aloft moves over the Front Range. 700mb temperatures are forecast to climb above 10c for the whole area, which translates to afternoon high temperatures in the upper 70s to upper 80s. The lowest elevations of western Nebraska may see highs around 90 with dry westerly winds. Other than some fire weather concerns, quiet weather is expected to start off the week with pleasant weather. Models do show a shallow cold front moving in from the north late Monday and Monday night, resulting in slightly cooler temperatures but remaining above average for mid May.

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 152 PM MDT Sat May 9 2026

The general pattern going into Tuesday is one of upper level ridging. A rather large high pressure system will be building over the Four Corners Region with an axis of it passing through. This should allow temperatures to reach the mid 70s to low 80s. We do have fire weather conditions showing up in the interior mountains near Rawlins this day. Humidities appear very low, possibly getting into the low teens with gusty conditions. Elsewhere, dry conditions may favor some elevated concerns. These conditons should persist into Wednesday where some spots in valleys east of the Laramie Range could reach the 90s and near daily record temperatures. Humidities plummet given the favorable environment for deep layer mixing. Relative humidities reaching the mid and low teens are a possibility. Attention to conditions these few days should be maintained for fire weather interests. Thursday a plume of monsoonal like moisture makes its way north from the Eastern Pacific into our area. The ridge gets pushed southeast into Texas allowing increasing chance of isolated to scattered showers and storms. PoPs are low at this time, and surface layer mixing will still be high creating dry conditions at the surface. So, the most likely outcome Thursday are the continued fire weather risk, but maybe throw in a few dry and windy thunderstorms. About this time a compact, but high amplitude trough will be passing over the northwestern Pacific Coast. Global models differ on the speed and strength of this feature. The GFS is much more aggressive with this trough and is a bit slower/south with the progression as it reaches our area Friday. ECMWF is a bit more progressive, weaker and northward with its trajectory. Both have the general negative tilt form to the trough which tend to be more dynamic than positive and flatter systems. The timing is somewhat important from a severe weather angle, a slower and more southward system may allow for the favorable left exit region of the jet to the south of the trough to be in phase with the better daytime heating. At the moment the models make this a more north and eastward event. A dry slot on the south side of the system will create sinking air and may tighten pressure gradients in the 700 mbar enough to create strong winds. Indeed our machine learning models highlight an elevated risk Friday morning and afternoon (~40%) for west to east mountain gap flow locations. Conditions area wide continue to by dry and warm, so fire weather is likely to continue, even going into Saturday. Fuels in our Nebraska Panhandle zones are not in good shape with little green up reported. The snowfall received on the eastern slopes and ridges of the Laramie Range has caused some greenup with vegetation. The periods of recent rain may stave off more critical fire concerns going into this period.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1130 PM MDT Sat May 9 2026

Upper level trough will move south of the region late tonight and early Sunday morning. Clearing skies and light winds are expected through much of Sunday. Can't rule out some low clouds and/or patchy fog

HAZARDS/WEATHER TRENDS: VFR conditions will prevail over the next 18 to 24 hours with clearing skies and relatively light winds. The only Aviation concern is the possibility of fog or low CIGS across the area, especially where rain fell on Saturday. Models struggling with this possibility and show probabilities around 10% to 25%. Will keep out of the TAFS and monitor through the morning hours, but did add some VCFG and low FEW-SCT cloudiness for a few terminals.

CYS WATCHES/WARNINGS/ADVISORIES

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