textproduct: Cheyenne

KEY MESSAGES

- Monsoon moisture will remain in place through the end of the week across the high plains. Heavy rainfall and localized flooding possible through Wednesday night.

- More heat returns this weekend through Monday, with some near record high temperatures possible along with drier conditions.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 211 PM MDT Wed Jul 29 2026

Scattered to numerous showers are expected this afternoon. Model and observational soundings show CAPE levels between 1000-1500 joules. However, the observational sounding from Ft. Collins has the most unstable Cape closer to the surface while the model soundings had more of the MLCAPE being the most unstable. DCAPE was also around 1200 joules with a slightly inverted V sounding, so gusty showers are going to be the highest threat from any storm or shower. Some small hail also can't be ruled out as shear is around 16kts. the weak shear will transform the environment from a stable on to a pulsy unorganized one. So with these temporary pulse ups, some BB to pea size hail may develop intermittently while as the storm collapses or recycles, wind gusts between 55 to 65 mph may occur in a wet microburst type outcome. Any potential severe thunderstorm warning that comes from the office today will most likely be from the "severe" wind threat. Around 00z or 6 PM a stream of vorticity will enhance the synoptic support for these thunderstorms near the border of Wyoming and Nebraska. Models consequently show the storm mode changing from discrete to a more linear storm mode. If the linear storm mode occurs then the wind threat and heavier rainfall threat will increase. These showers are likely to last until 10 pm then the synoptic forcing significantly decreases as the overnight period progresses.

Thursday into Friday, The central high pressure of this upper level ridge starts to meander westward back towards the four corners region. Hi-res models show an isolated to scattered shower risk Thursday afternoon and evening as a result from another weak shortwave moving through the Intermountain West. Looking the at 700mb RH parameter, models may be drying out the lower regions a little more quickly than what is realistic in a monsoonal moisture environment. However, any severe potential will most likely confined to any severe wind risk much like today. NAEFS is also capturing the westward shift of central pressure and forecasting increasing mid- level temperatures closer to the 90th percentile for Southeast Wyoming. Daily forecasted high temperatures are slated to slowly shift back into the 90's across the forecast area as that warm air advection increase as well as lower afternoon humidity levels to prop up the potential for heat advisories and elevated fire weather concerns for this weekend.

LONG TERM /SATURDAY THROUGH TUESDAY/

Issued at 211 PM MDT Wed Jul 29 2026

A ridge axis will be firmly in place for our Saturday with dam heights above 594 decameters for a good portion of the area. This high pressure will also suppress the monsoonal moisture flow and keep it well to our south. The sinking and downsloping air should help dry and heat up the afternoon atmosphere. Expect high temperatures ranging from the mid to upper 80s in the interior basins and foot hills to low to upper 90s north and east of the Laramie Range. Some locations in Converse and Niobrara Counties could reach or exceed record daily high temperatures. Another area of concern with the excessive heat is how dry it will be. Minimum afternoon humidity values are progged to be in the lower 20s to the low teens and single digits for the northern and western fire zones. Winds appear tame and are expected to preclude red flag conditions. A few isolated storms are possible in the mountains and very southern portions of the CWA during the afternoon hours with just enough moisture to kick off high based thunderstorms. Would not expect these storms to last long or produce much rainfall.

Sunday and Monday still has the ridge axis over the area. There may be a few weak shortwave troughs that could flatten the ridge slightly. The probability of a few more afternoon thunderstorms could result, but chances are low and storms would be dry. The main concern is for the excessive heat Sunday. Again temperatures soar to the upper 90s to mid 100s for many locations. The current forecast is for daily record highs to be broken or tied. Winds do increase also Sunday with the increasing pressure gradients influenced by the shortwave troughs. RH values plummet into the single digits over a large part of the area and overnight recoveries are likely to be poor. Therefore it is probable red flag products are issued if these conditions hold in the forecast.

Monday evening through the rest of the forecast period has ensemble support of a trough clipping the border and extending south through our area. This would suppress the ridge into the deep southwest and allow more seasonable conditions to return. Moisture remains a scarce commodity, but perhaps there is enough along with enhanced synoptic lift to trigger some showers and storms, especially over the ranges. Hopefully a cold front associated with this trough can provide some relief from the heat and increase surface humidity.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1118 AM MDT Wed Jul 29 2026

WYOMING TERMINALS: More thunderstorms and showers develop over the mountains around 20z to 01z before pushing east this afternoon into late evening. Heavy to moderate rainfall and gusty winds are possible for the western terminals (KCYS, KLAR, and KRWL). Once the thunderstorms and showers move out, expect visibility and wind speeds to improve.

NEBRASKA TERMINALS: At Nebraska terminals today expect mostly clear skies through the middle afternoon hour. Starting around 21z storm and shower activity will move in from Wyoming. Periods of MVFR or IFR conditions could occur at terminals particularly at KBFF and KCDR. Variable winds gusting to 40 to 45 knots possible along with reduced visibilities. Activity clears by about 3 to 5z and sky conditions begin clearing. There is the possibility of reduced CIGs and visibility post rain, but the chances are too low to include in TAFs and total surface saturation appears uncertain.

CYS WATCHES/WARNINGS/ADVISORIES

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