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 MONDAY NIGHT/

Issued at 1249 PM MDT Sun Jul 19 2026

Typical summertime weather will continue over southeast Wyoming and western Nebraska throughout the short-term period. The center of the ridge at 500mb will shift slightly farther south both this afternoon and tomorrow, generally positioning itself over the northern Four Corners region. This will allow for a slight increase in moisture over the mountains of southeast Wyoming as a bit of monsoonal moisture spills over the top of the ridge axis. PWAT values will inch upward and as a result, we can expect a slight increase in shower and thunderstorm coverage over the Snowy, Sierra Madre, and northern Laramie ranges. Most thunderstorm activity will remain quite brief and localized, generally resulting in only a few hundredths of an inch of liquid. However, a few instances of briefly gusty wind may accompany the strongest storm cores given DCAPE values above 1500 over most of the Wyoming high country.

The other story will be high temperatures, which will be slightly enhanced both today and on Monday due to a slight increase in downslope westerly flow from the west as the ridge sags to the south. Heat Advisories remain in effect for the northwest NE panhandle on Sunday, and expand to include areas in east central Wyoming and most of the NE panhandle on Monday. Consideration was given to a heat advisory product for Cheyenne and eastward to Sidney. However, afternoon high temperatures remain just below the 99th percentile of July highs. If forecast guidance for tomorrow comes in warmer, an advisory may be necessitated in the overnight forecast package. Despite the hot afternoon weather, relatively dry forecast soundings will result in overnight lows running near to only slightly above average through the period.

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 1249 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 /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1125 AM MDT Sun Jul 19 2026

VFR is expected to continue for eastern WY and western NE terminals through midday Monday as clouds bases hold at or above 10kft and visby above 6 SM. The primary aviation weather concern will be isolated to scattered showers and perhaps thunderstorms this afternoon and evening. Gusty erratic winds will accompany any activity, but anticipated coverage precludes any mention besides VC at this time. Winds should become light and variable overnight.

CYS WATCHES/WARNINGS/ADVISORIES

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