textproduct: Cheyenne

KEY MESSAGES

- Hot, dry, and breezy conditions continue through Sunday before a much awaited cold front arrives for the start of the week.

- Monday looks to be the last 100+ day for the upcoming week or so, with reduced fire concerns also arriving with cooler weather.

- Monsoonal moisture will attempt to return as early as Monday, leading to increased precipitation chances through much of next week.

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 220 PM MDT Fri Jul 17 2026

The short term should remain fairly similar to the last several days as high pressure ridging continues to sit over the region with warm temperatures today in the upper 80's to near triple digits, increasing a few degrees with nearly widespread 90's to 100's across the area on Saturday. Because of this increase in coverage of triple degree heat, a Heat Advisory was issued beginning Saturday for portions of Sioux and Dawes counties, with several more zones added in beginning on Sunday. We should also continue to see elevated fire weather conditions as surface relative humidity values sit in the 15-20% range while breezy, diurnally driven winds of around 20-25 mph will be present, but if any site is able to reach critical criteria for fire weather conditions it's not expected to persist for 3 or more hours. Finally upslope flow today may once again fuel an isolated shower or storm across our high elevation and mountainous locations in Carbon and Albany Counties, but with inverted V sounding profiles precipitation may struggle to reach the ground under weaker cells, and instead we could see the potential for a rogue dry lightning strike or gusty outflow winds. Monsoonal moisture attempts to finally swing into the region on Saturday, but guidance has dialed back or precipitation chances with Carbon and Albany County once again at an isolated to widely scattered probability of seeing some development. Better moisture should return just beyond the short term on Sunday and thereafter.

LONG TERM /SUNDAY THROUGH THURSDAY/

Issued at 220 PM MDT Fri Jul 17 2026

Sunday...GFS progs the ridge aloft over the northern Rockies to be flattened somewhat with zonal flow developing over Montana and northern Wyoming. A weak perturbation, or shortwave trough aloft, will move across our counties in the afternoon and evening, with monsoonal moisture advecting into our western counties west of I-25, where we anticipate scattered showers and thunderstorms to develop in the afternoon west of I-25, with the greatest areal coverage over the Snowy, Sierra Madre and northern Laramie Ranges. So, more beneficial rain will occur.

Monday...Monsoonal moisture at low and mid levels increases further, aiding in another increase in late day shower and thunderstorm coverage, and beneficial rains, with coverage increasing to scattered 30 to 60 percent POPS, probability of measurable precipitation, with the greatest coverage over and near our mountain zones.

Tuesday-Friday...A relatively significant pattern change will occur, with "beware" northwest flow aloft developing along with a decent increase in low and mid level moisture and upslope southeast mechanical lift at low levels, and occasional passing shortwave troughs aloft, helping to produce scattered to numerous showers, and scattered thunderstorms in the afternoons and evenings, with beneficial rainfall and possibly some locally heavy rains from some of the slower moving thunderstorms. The most likely locations for locally heavy rain and the greatest areal coverage may be along and east of Interstate 25. On Friday, the GFS progs the last of the passing shortwave troughs aloft to move into Nebraska by evening, with shortwave ridging aloft bulging across Wyoming, thus expect an attendant decrease in areal afternoon and evening shower and thunderstorm coverage.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1125 AM MDT Fri Jul 17 2026

A 5940 meter plus 500 mb ridge aloft will remain parked over our region through Saturday afternoon, squelching all but isolated afternoon and evening showers and thunderstorms over the Sierra Madre Range, with dry conditions elsewhere. At the surface, a surface low pressure trough will develop late tonight from Douglas to Alliance, with an attendant warm front extending eastward in the aforementioned trough axis. North of the warm front, easterly upslope winds will likely aid in the development of low clouds and some fog for KCDR and KAIA late tonight and early Saturday morning.

Wyoming TAFS...Confidence is high in VFR conditions prevailing with isolated late afternoon and early evening showers and thunderstorms over the Sierra Madre Range, and dry conditions elsewhere. Scattered high based cumulus will occur through early evening. Mix down and surface pressure gradients will aid in producing gusty winds of 20 to 30 knots through early this evening, with winds then subsiding.

Nebraska TAFS...High confidence in VFR conditions prevailing with scattered high based cumulus clouds through early evening. A warm front will develop late tonight from roughly Douglas to Alliance, with northeast to southeast low level winds producing likely MVFR ceilings and visibilities in low clouds and fog at KCDR and KAIA from 09Z to 13Z. Otherwise, clear skies will prevail. Mix down and surface pressure gradients will aid in producing gusty winds to 22 knots through early evening, then winds will subside.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Heat Advisory from noon Sunday to 6 PM MDT Monday for WYZ101- 102-108. NE...Heat Advisory from noon Saturday to 6 PM MDT Monday for NEZ002- 095. Heat Advisory from noon Sunday to 6 PM MDT Monday for NEZ003- 019>021-096.