textproduct: Cheyenne

KEY MESSAGES

- A few widely scattered thunderstorms will remain possible through Friday evening.

- Another heat wave will build into the area Saturday through Monday, producing near record high temperatures Sunday.

- Elevated to near critical fire weather conditions are expected Sunday and Monday.

- Some relief of the heat is possible during the middle of next week as a Canadian cold front moves towards the Front Range.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 225 PM MDT Fri Jul 31 2026

Some moisture lingers over the area today as a subtle vort-max rides over the top of the amplifying ridge locked in over the southwestern CONUS. Low level moisture return did not quite meet expectations this morning, so the boundary layer remains fairly dry today despite better moisture aloft. Weak instability is present mainly along the Laramie Range in southeast Wyoming, while stronger CIN is apparent further east. This is helping to support isolated to widely scattered showers and thunderstorms. While parameters are not very favorable for severe weather today, small hail and a few rogue strong wind gusts will be possible through the evening hours. Expect storms to struggle once they run into the capping further east over the High Plains. Look for clearing skies overnight with temperatures falling to near seasonal averages.

The heat will build in this weekend as a powerful upper level ridge builds in over the Great Basin. A Pacific trough pushing into the Pacific northwest will then amplify ridge on its northeastern flank, sending temperatures soaring once again this weekend. Saturday looks like a transition day. 700-mb temperatures won't be too extreme over our eastern zones, but Wyoming wil be already approaching the 90th to 97.5 percentile. We should remain below daily record highs, but it will certainly be a hot day. The I-80 corridor is expected to reach the upper 80s to lower 90s, while areas to the north can expect mid to upper 90s. Probabilities for 100F or higher are around 40% in Chadron, and 10% for locations along the North Platte River valley. As we head into Saturday night, falling surface pressure over western Wyoming and Montana will increase the pressure gradient over the High Plains and lead to increasing southerly winds. Wind gusts of 30 to 40 mph will be possible at times, likely supporting very warm overnight lows Saturday night into Sunday morning.

Sunday brings the CWA chances to beat record high temperatures. Dry air in the low and mid levels, a strong 500mb ridge axis over the four corners, and 700mb temperatures in the 20 to 23 Celsius range all make a great setup for high temperatures. Southerly wind in the Nebraska panhandle are leading to elevated to near critical fire weather. The southerly winds are upsloping off the Cheyenne Ridge area, keeping Cheyenne slightly cooler than most of the CWA, and keeping the area just shy off heat records. Winds are looking to downslope off of the Pine Ridge, helping to increase temperatures near Chadron to potential all time highs. Maximum temperatures west of I-25 are expected to be in the mid 90s to near 100 degrees, and temperatures east of I-25 to be in the upper 90s to near 108 degrees. Most temperatures across the area are at or near the 99th percentile and/or all time maximum temperatures. The hottest temperatures are expected to be in Sioux, Dawes and Box Butte Counties in the northern Nebraska panhandle. With these high temperatures and dry air, a Heat Advisory has been issued for a good portion of the CWA.

LONG TERM /MONDAY THROUGH THURSDAY/

Issued at 225 PM MDT Fri Jul 31 2026

On Monday, the ridge flattens somewhat as a shortwave trough aloft and its associated cold front enter our counties from the north, cooling off temperatures rather significantly across our northern counties and there may be enough available moisture for isolated late day thunderstorms over the southern Laramie Range.

Then on Tuesday, expect a relief from the summertime heat in the wake of a passing Canadian origin cold front, sending maximum temperatures back into the mid 70s to mid 80s. Moisture looks scant, perhaps enough for isolated to widely scattered late day thunderstorms near the southern mountains.

For your Wednesday...Brisk west northwest flow aloft continues and with progged 700 mb temperatures near 18C, we anticipate maximum temperatures to rise into the 80s. Models indicate a dry punch at low and mid levels, effectively cutting off any convection chances due to warm temperatures aloft producing plenty of CIN, Convective Inhibition.

Then on Thursday...The heat returns in the warm sector that our counties will be in to the warm side of the cold front, with maximum temperatures well into the 90s at most locations. With scant low and mid level moisture, no showers or thunderstorms are expected.

For your Friday, the end of the traditional workweek...the heat continues with highs in the 90s. Not totally buying the GFS progged Canadian origin cold front sweeping across our counties and providing heat relief, though your National Weather Service forecast team will monitor future model trends to see if the cooler push will come to fruition. Continued dry with limited atmospheric fuel, moisture availability.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1141 AM MDT Fri Jul 31 2026

While a persistent ridge aloft stretches from western Montana to Arizona today, a weak weather disturbance or shortwave trough aloft will slide down our forecast area on northwest flow aloft, producing isolated to widely scattered showers and thunderstorms along and near the I-25 corridor this afternoon and early evening. Ridging bulges across Wyoming and Nebraska on Saturday, effectively ending any chances for afternoon and evening showers and thunderstorms due to warm temperatures aloft.

Wyoming TAFS...Only made some minor changes due to high confidence in the long standing experience of our midnight shift forecaster and the inherited TAFS. Looking at the 12Z NAM and latest HRRR runs, expect isolated to widely scattered showers and high based thunderstorms to continue to develop this afternoon through early evening along an 850/700 mb theta-e ridge axis parallel to I-25. So, confidence is high enough to include PROB30s at Laramie and Cheyenne with wind gusts up to 35 knots. VFR prevails. Clouds clear out after early evening. Wind gusts to 23 knots through sunset due to surface gradients and adiabatic mix down winds.

Nebraska TAFS...High confidence that no showers or thunderstorms will occur due to limited available moisture and warm temperatures aloft producing enough convective inhibition, CIN, to keep it dry. VFR prevails. Wind gusts to 25 knots until early evening due to surface gradients and mix down winds. Will see some flat cumulus development through early evening.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Heat Advisory from 11 AM to 9 PM MDT Sunday for WYZ101-102-104- 107>109-111-118-119. NE...Heat Advisory from 11 AM to 9 PM MDT Sunday for NEZ002-003- 019>021-054-055-095-096.