textproduct: Cheyenne

KEY MESSAGES

- Warming and drying trend expected through the end of the week.

SHORT TERM /THROUGH THURSDAY/

Issued at 441 AM MDT Wed Sep 2 2026

Today, the upper-level ridge continues to build over the Central US with the back side of the ridge pushing into the Intermountain West as the ridge broadens out. Another weak shortwave Looks to move through the intermountain west developing some chances for weak showers this afternoon and evening. Model guidance shows a few vort-maxes to accompany this wave but overall, the synoptic support is pretty weak. MLCAPE and surface-based CAPE values are both only a couple hundred joules despite some moisture being advected in while in southwest flow. The areas with the highest chances are going to be the mountainous and mountain adjacent regions of Albany, Carbon, and Laramie counties in Southeast Wyoming. Bulk shear also starts out fairly weak around 20 to 30kts and increases as the evening progresses. However, once the sun goes down we lose almost all instability across the forecast area as bulk shear becomes in an acceptable range of 35 to 45 knots aloft. So there is a chance that as the sun goes down these showers become pulse-y short lived thunderstorms where the greatest threat will become lightning and gusty winds underneath the storms. Past 6pm uncertainty increases for the showers/storms being strong enough to produce rain before dissipating shortly after sunset. Winds will be slightly gusty between 30 and 40 mph for areas west of I-25 today and Thursday afternoon as the waves tighten the gradient as they move through the Intermountain West. There are less chances for showers Thursday afternoon as RH values drop between 12 and 20 percent for elevated to borderline Red Flag conditions. However, the strongest winds dont line up with the areas of lowest RH. So, confidence in reaching Red Flag criteria is low but the areas with the strongest winds only look to drop into the 20 and 30 percent range (Albany, Carbon, and Laramie County). So, no fire weather products were issued during this time.

LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/

Issued at 155 PM MDT Tue Sep 1 2026

Friday...Although a bit of pseudo monsoonal moisture at mid levels will be over our forecast area, the deeper moisture on southwest flow aloft will remain over Colorado and New Mexico, thus continued dry for us. 700 mb temperatures suggest summer like heat will continue for warm weather lovers.

Saturday...Low and mid level moisture increases somewhat via precipitable water content, and the deeper moisture will create widely scattered showers and a few thunderstorms from the Laramie Valley to near Douglas and nearby locations in the afternoon and evening hours. Dry elsewhere. The decent 700 mb temperatures will aid in keeping similar temperatures to Friday.

Sunday...Beneficial rains look quite promising as there will be an increase in precipitable water values via a better monsoonal moisture tap. The combination of passing shortwave troughs aloft and low level mechanical lift and orographic effects will help produce scattered afternoon and evening showers and thunderstorms, most numerous over and near the mountains.

Monday...With adequate low and mid level moisture availability combined with upslope lift and passing shortwave troughs aloft, expect scattered afternoon showers and thunderstorms mainly over and west of Interstate 25, with the showers and thunderstorms propagating and developing mainly east of I-25 in the evening. Still some uncertainty with regard to maximum temperatures, as an early September cold front may pass across our counties bringing in a refreshing respite from the heat. With still so much uncertainty, will leave the warmer temperatures as is to blend in with our neighboring offices, but this day will likely be cooler than currently forecasted.

Tuesday...An autumnal like pattern greets us synoptically for September with a rather significant shortwave trough aloft traveling eastward across Montana. Still enough atmospheric moisture to produce scattered showers and thunderstorms south of a Rawlins to Scottsbluff line. Again, temperatures may be cooler than currently forecasted with later model runs and trends.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 521 AM MDT Wed Sep 2 2026

A shortwave will push through this afternoon and evening for possible shower chances. The highest chances for showers is between 21z and 00z for KCYS and KLAR. However, There is almost no energy for showers to sustain themselves meaning its hard to tell how much rain will fall if any falls over the terminals. VCSH was used because there was no consensus between hi-res models for timing and intensity. The 12z model runs should provide enough confidence to upgrade to Prob30 in the TAFS. These showers look to be somewhere between 10,000ft and 15,000ft so VFR conditions are expected throughout the TAF period.

CYS WATCHES/WARNINGS/ADVISORIES

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