textproduct: Cheyenne

KEY MESSAGES

- Scattered strong to severe afternoon and evening thunderstorms are expected today, mainly east of I-25. While all severe hazards are possible today, large hail is the primary concern.

- Widely scattered strong to severe thunderstorms are possible again on Tuesday, mainly south of the North Platte River.

- Thunderstorm chances continue on Wednesday and Thursday with greater coverage storms increasing the potential for localized flooding concerns, particularly over recent burn scars.

- Warming temperatures, falling humidity, and increasing winds will increase fire weather concerns this weekend.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 215 PM MDT Mon Jun 22 2026

Another round of active weather is anticipated today across the area. The morning deck of low clouds burned off quite quickly this morning. We still have a little bit of MLCIN remaining in the central and norther Nebraska panhandle, but this continues to weaken. Otherwise, a fairly potent convective environment is present across the area early this afternoon. A sharp dryline is locked up against the Laramie Range as a surface high with plentiful moisture flux from the southeast remains in place to the east. An upper level low well to our north is carrying a modest upper level jet streak with it which is supporting strong deep layer shear over the area. Effective bulk shear is around 40 to 50 knots at this time, and is progged to increase gradually through the evening, locally exceeding 60 knots later. Ample instability is also present, with MLCAPE 1000 to 1500 J/kg already, and expected to increase closer to 2000 J/kg later this afternoon. This sets the stage for scattered strong to severe thunderstorms today. Coverage will not be all that high today, but there is potential for several discrete supercells. The primary concern is large to very large hail, but these types of storms are capable of producing all severe weather hazards, including a few tornadoes, strong winds, and localized flash flooding. The tornado risk will increase later in the afternoon into the early evening as a surge of the low-level jet enhances the low- level wind shear, but confidence is lower in the tornado threat. A Severe Thunderstorm Watch is in effect until 8PM today, but portions of the area may see a strong storm lingering for another hour or two after that. While the watch includes the I-25 counties, the primary concern is east of the I-25 corridor. We will also need to watch for a storm passing directly over the South Fork fire burn area, as today's storms will produce locally heavy rainfall, and thus a limited flash flood concern over the fresh burn scar.

Overnight tonight, the shortwave trough passing to our north will continue to produce overrunning ascent as a surface cool front tries to push southward. Elevated instability will continue through the night as well. Hi-res models are in good agreement showing fairly widespread activity across south Dakota, but parameters are generally not too different for our area. While hi-res models don't show much here, the forcing and parameters are enough to keep 20 to 40% PoPs running through the night along and north of the North Platte River valley. The overnight moisture return will have the potential to produce patchy morning fog and low clouds once again to begin Tuesday. Expect to start off the day with breezy north to northeast winds as well.

Tuesday will have a somewhat different setup across the area in the wake of tonight's cool front. Decent upslope flow will keep cooler and moist conditions in place over much of the High Plains. Expect a strong cap to develop over much of the area. South of the North Platte River valley, the cap will be a bit weaker, and thus more likely to erode later in the day. As a result, the primary area of concern is in southeast Wyoming along the I-80 corridor (plus Platte County). This could extend into Goshen and the southern panhandle, but confidence is lower there. As today, the primary concern will be large hail once again.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Issued at 215 PM MDT Mon Jun 22 2026

Wednesday...West northwest flow aloft continues, while a shortwave trough aloft moves over eastern Wyoming near peak heating. A decent low level convergence boundary will stretch across southeast Wyoming in the afternoon, with an 850 and 700 mb theta-e ridge axis extending from Casper to Cheyenne. Expecting scattered afternoon and evening thunderstorms to initiate in the convergence boundary, and with CAPE of 1000 to 2000 J/kg and bulk shear values near 45 knots, we should see isolated to scattered strong to severe thunderstorms develop from afternoon through early evening, and concur with the Storm Prediction Center outlook of marginal to slight risk over our eastern half of counties.

Thursday...Westerly flow aloft continues, and with surface low pressure developing over south central Wyoming producing a convergence axis from Douglas to Laramie, and plenty of low and mid level moisture, and 850/700 mb theta-e ridge axis from Casper to Cheyenne, along with CAPE of 1000 to 1800 J/kg and bulk shear near 50 knots, we anticipate some storms to become severe, with large hail and damaging winds as the primary threats east of I-25, with some locally heavy rainers due to flow aloft.

Friday...Low amplitude ridging develops over our forecast area, with some drier air noted advecting in. However, still expect isolated to widely scattered afternoon and evening thunderstorms to form along a low level convergence axis along the I-25 corridor. A few strong and possibly severe storms may occur.

Saturday...The flow aloft turns southwest and increases in speed, with considerably drier air moving across our counties, producing a dry day with a warming trend as 700 mb temperatures spike near 19 Celsius.

Sunday and Monday...A broad trough aloft develops across the northern and central Rockies, with dry southwest flow aloft, leading to only isolated to widely scattered thunderstorms in the afternoons and evening. Slightly cooler compared to Saturday in the wake of a cold frontal passage.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1107 AM MDT Mon Jun 22 2026

A weather disturbance aloft will move over western Nebraska late this afternoon and will combine with adequate low and mid level moisture to produce isolated to scattered afternoon and evening thunderstorms today across far southeast Wyoming and the Nebraska Panhandle.

Widespread low clouds and fog will occur after midnight tonight along and east of I-25 including TAF sites at Cheyenne and the Nebraska Panhandle. MVFR ceilings will continue much of Tuesday morning for TAF sites east of I-25.

Wyoming TAFS...High confidence in VFR at Laramie and Rawlins, with sufficient surface gradients to produce wind gusts to 30 knots until 01Z.

For Cheyenne, high confidence in VFR through 08Z, with IFR in low clouds and fog thereafter and ceilings rising to MVFR after mid morning Tuesday. Sufficient surface gradients to produce wind gusts to 26 knots until 01Z.

Nebraska TAFS...High confidence in VFR continuing until around 08Z, with isolated to scattered thunderstorms at each site from 20Z to 02Z, producing a few wind gusts in excess of 45 knots and visibilities under three miles at times. High confidence in widespread IFR developing after 08Z, due to ceiling and visibility restrictions. Visibilities will improve above six miles after 15Z Tuesday, with ceilings improving to MVFR.

CYS WATCHES/WARNINGS/ADVISORIES

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