textproduct: Cheyenne

KEY MESSAGES

- Hot, dry, and breezy conditions continue through Monday.

- Monsoonal moisture will attempt to return by Tuesday resulting in increased precipitation chances through much of the week.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 221 AM MDT Mon Jul 20 2026

One more hot day is expected on Monday as the upper-level ridge sits directly over Wyoming. Most locations across the area will see highs in the 90s to low 100s, which is about 5 to 10 degrees above average for this time of year. Heat Advisories remain in place for portions of southeast Wyoming and western Nebraska through 6 PM this evening. Hot temperatures will lead to dry conditions at the surface, though a weak disturbance moving through the ridge could spark some showers and thunderstorms as PWATs remain elevated due to a push of monsoon moisture. Hi-Res guidance shows a few showers developing early in the afternoon, with coverage increasing into the evening hours. Severe storms are unlikely, however, cannot rule out an isolated severe wind gust with DCAPE values over 1600 J/kg. Brief heavy rain will also be possible in showers and storms as monsoon moisture bumps PWATs closer to 1 inch. Some models are hinting at the potential for some isolated nocturnal convection as well as some surface based CAPE will exist. However, it seems that Hi-Res guidance is starting to decrease overnight storm chances.

A shortwave digging down from Canada will send a cold front across the area Monday night. Temperatures on Tuesday will be noticeably "cooler", falling about 10 degrees compared to Monday's highs. Increased moisture into the area from a proper surge of monsoon moisture will lead to increasing cloud cover throughout the day. Instability and PWATs in the 90th percentile will lead to storm development during the afternoon hours. Hi-Res guidance shows widespread showers and storms developing west of the Laramie Range. Cloud layer winds are on the slower side per model soundings. Slow storms combined with high PWATs will lead to a heavy rain threat with the potential for flash flooding. Showers are likely to continue into the overnight hours and spread eastward with the heavy rain threat also spreading eastward.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Issued at 1250 PM MDT Sun Jul 19 2026

Monsoonal moisture arrives in bulk to southeast Wyoming and western Nebraska by Tuesday and will last throughout much of the long-term period. The primary reason for the increase in monsoon moisture will be a lobe of enhanced PWAT values, originating from the eastern Pacific in the vicinity of a decaying tropical system drifting north. This, combined with a more favorable position of the ridge over the southern Four Corners region, will direct more saturated profiles eastward across the Great Basin and through the I-80 corridor. After a slight increase in thunderstorm coverage and chances on Tuesday, the peak of this surge of moisture will arrive for the convective afternoon timeframes on Wednesday and Thursday when PWAT normalized anomalies exceed the 75th percentile of climatology. The thermodynamic setup combined with relatively light wind speeds aloft will favor some slow storm motions. Flash flooding will be possible in areas that see repeated rounds of thunderstorms or any storms that remain stationary for long periods of time. For now, the best chances of this appear to be in the higher elevations of southeast Wyoming as well as the adjacent foothills of the Snowy, Sierra Madre, and Laramie ranges. Ultimately, outflow boundary interactions will ultimately determine where the heaviest rain falls - details that generally can not be anticipated until the day of the event. Overall, expect afternoon high temperatures to drop back notably thanks to increased cloud cover and slightly lower mid-level temperatures from Tuesday through the end of the week. By Friday evening and into early next weekend, ensemble guidance suggests that the monsoonal push will drift eastward and lower PWAT values will return to the Rockies/High plains. This may ultimately result in lower precipitation chances and warmer temperatures by next weekend.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 525 AM MDT Mon Jul 20 2026

Minimal aviation concerns are expected during the day with mostly sunny skies. VFR conditions will prevail with normal diurnal wind gusts of 20 to 25 kts possible during the afternoon hours. There is a chance of scattered showers and storms during the afternoon and evening hours. Storms could contain gusty winds.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Heat Advisory until 6 PM MDT this evening for WYZ101-102-108. NE...Heat Advisory until 6 PM MDT this evening for NEZ002-003- 019>021-095-096.