textproduct: Cheyenne

KEY MESSAGES

- Shower and storm chances are expected through the rest of this weekend and later on Monday. Strong to severe wind gusts will be possible Sunday, with moderate to heavy rain possible Sunday and Monday.

- Marginal Risk for severe thunderstorms Sunday with strong gusty winds up to 65 MPH possible.

- Drying and warming trend expected going into mid to late week with growing potential for elevated fire weather conditions.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 155 AM MDT Sun Aug 30 2026

Some nighttime/early morning convection continues to track east over Carbon and Albany counties based on current KCYS radar. This activity is likely in response to a potent secondary shortwave and a 90kt jet shifting east into central Wyoming at this hour. Some weak mid to upper level forcing will continue prior to sunrise along with 100 to 300 j/kg of elevated CAPE across mostly southeast Wyoming. This should be enough for widely scattered rain showers and embedded thunder...so added a slight chance of thunder to the forecast until 8 AM. Added POP further east towards the I-25 corridor with high res models showing some scattered showers impacting Cheyenne and Wheatland early this morning. A few cells may contain heavy rainfall near the Colorado border through noon.

A bit of a tricky forecast for Sunday and Sunday evening. Models all show enhanced upper level difluence in the right-entrance region of the 90-100 knot jet max across central Wyoming today as it and a series of potent upper level disturbances track east or northeast. Although the low to midlevels of the atmosphere appear pretty worked-over from yesterday's convection (and possibly this morning) with model soundings showing lower lapse rates and limited CAPE compared to Saturday, concerned that we may see another round of (several) lines of thunderstorms moving across the area today due to the forcing alone. Thankfully, it will generally be cooler today with highs in the 70s to low 80s for most of southeast Wyoming, and mid 80s to low 90s for western Nebraska. Instability doesn't appear as high as Saturday, but models are still showing 300 to 800 j/kg MLCAPE into the afternoon which is enough to produce widely scattered/scattered thunderstorms. A Marginal Risk for strong gusty winds remains over most of the forecast area, but do not think gusts will be as strong as yesterday. In addition, very heavy rainfall is certainly possible with some of these storms today, mainly across southeast Wyoming. Kept POP between 30 to 60 percent along and west of I-25...with more isolated coverage further east and northeast across east central Wyoming and western Nebraska. Expect this convection to dissipate rather quickly this evening as the jet axis lifts northeast tonight. Other than that, breezy to locally windy conditions are expected for most of southeast Wyoming due to a decent surface pressure gradient but also the upper level jet nearly overhead. Expect wind gusts of 35 to 45 MPH, mainly Carbon and Albany counties and east central Wyoming (higher gusts possible in and near thunderstorms).

Unsettled weather continues into Monday, but this time later in the day. All models show a potent upper level trough lifting northeast out of the southwest US. Primary trough axis will be a slow mover and over Utah extending east into northern Colorado by late Monday afternoon into Monday evening. It is expected to lift northward into southern Wyoming Monday night. Expect mid to high cloudiness to push north ahead of the trough through the day...which may greatly limit low to midlevel instability and CAPE. At this time, model soundings show a respectable 500 j/kg of MLCAPE and elevated CAPE into the evening hours. Some decent forcing is noted ahead of the trough, with enhanced midlevel OMEGA along and just north of I-80 due to some low level convergence, remnant instability, and mid to upper divergent flow. Some ensemble members show a potential for widespread moderate to heavy rainfall with QPF amounts above a half inch along the I-80 corridor and the North Platte River Valley...tapering off as you head further north. However, all high res guidance isn't too excited about the prospect of heavy rainfall with prog reflectivity showing some light showers lifting north and weakening as they push north of I-80...but not much deep convection. Kept POP around 60 percent for the I-80 corridor, with values closer to 30 to 40 percent across east central Wyoming and the northern/central NE panhandle. Kept QPF around a tenth to two tenths of an inch for now due to low confidence with higher amounts between 0.50 to 0.75. Remaining near average for this time of the year with highs in the mid 70s to mid 80s for most locations (warmest east of I-25).

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 135 PM MDT Sat Aug 29 2026

We will be on a dry and warming trend through the rest of the long term as flow aloft laxes and moisture decreases. While most of the upper level disturbances stay west and north, there may be enough lingering monsoonal moisture to keep a few PM showers and thunderstorms going. Widespread rain is not expected given the dry near surface conditions. Minimum afternoon RH values in the mid to low 20s and gusty winds could promote elevated fire conditions, mainly in the northern and western counties. This drying pattern is on track to be reinforced in the very long term as the ridge builds back west and the jetstream stays out of our area.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 600 AM MDT Sun Aug 30 2026

Another round of thunderstorms expected today as a potent jet stream and midlevel disturbance move northeast across the area. Thunderstorms won't be as numerous as Saturday, but locally heavy rainfall and gusty winds are possible, mainly across the southeast Wyoming terminals into early this evening.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail with brief MVFR possible for the southeast Wyoming terminals as a line of thunderstorms pushes across KRWL, KLAR, and KCYS between 19z and 00z Monday. Wind gusts up to 55 knots, very heavy rainfall, and frequent lightning possible as these storms move rapidly to the east. Not as confident with most of the western Nebraska terminals, so kept VCSH in the TAF for now. Windy conditions expected today for KRWL and KLAR, even without thunderstorm activity, with gusts up to 35 knots between 14z and 23z.

CYS WATCHES/WARNINGS/ADVISORIES

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