textproduct: Cheyenne

KEY MESSAGES

- Isolated strong to severe thunderstorms are possible over the Nebraska panhandle Saturday afternoon and evening.

- Critical fire weather conditions are ongoing Saturday over much of southeast Wyoming with strong southwest winds, low humidity, and warm to hot temperatures.

- A few showers moving in from the west this afternoon will have the potential to produce gusty and erratic winds in southeast Wyoming.

- Elevated fire weather conditions continue Sunday, with more widespread critical conditions possible Monday. Elevated fire weather conditions will continue for much of the week ahead.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 131 PM MDT Sat Jun 27 2026

An unseasonably strong upper level low is circulating over the Pacific northwest today, bringing a change in the weather after the stormy pattern over the last several days. Over southeast Wyoming, dry air in the dry slot of this upper level low is mixing down, and pushing the surface dryline eastward. While this has been slower than modeled earlier today, all of southeast Wyoming except Torrington and Lusk have seen dewpoints plummet. Gusty southwest winds in combination are leading to increasing fire danger. While there is some uncertainty concerning how the recent rainfall might have affected fuel conditions, a Red Flag Warning was issued for the Wyoming High Plains out of caution, as weather conditions are certainly meeting criteria. Fuels west of the Laramie range are still in green-up status, so no headlines will be issued there. However, fairly significant weather conditions are expected with southwest winds gusting 50+ mph and RH dropping to around 10%. In addition, a cool front will arrive late this afternoon (pushing in around 6PM to our western zones). Expect an abrupt wind shift to the west or WNW. In addition, expect to see some high-based showers developing along the boundary and pushing into Carbon and Converse counties. These will have the potential to produce locally gusty and erratic winds. With the strong background flow already in place, it won't take much to exceed 60 mph with this activity.

Plentiful low-level moisture is still in place east of the dryline, which has been slower to advance than expected earlier. With dewpoints still close to 60 degrees and temperatures warming into the 80s or even low 90s, we have ample instability in place east of the dryline. There is still a bit of CIN remaining as of this writing, but models are in fairly good agreement burning this off by 3PM or so. Once that happens, expect to see some convection developing along the dryline and moving off to the northeast. Vertical wind shear isn't too strong today, but it is sufficient to get a few strong to severe thunderstorms going. The risk area today is confined to those east of the dryline, so mainly just the Nebraska panhandle. Storms may take a moment to get going too, so the Chadron to Alliance corridor is the only portion included the Level 2 of 5 (Slight) risk for severe weather by the Storm Prediction Center today. Thunderstorm potential will wind down around 9PM.

A cool front will push through the area from the northwest this evening, shifting winds abruptly to the west or WNW. Temperatures should cool down to near seasonal averages by Sunday morning. Sunday will be a touch cooler, and thus slightly higher humidity. Fire weather conditions will still be elevated, but concerns for critical conditions are confined to Laramie County at this time. The thunderstorm threat will also be more limited Sunday. We'll have a frontal boundary stalled straddling our area through the day, but by the late afternoon or evening hours the trough to our northwest will initiate some warm air advection overtop the boundary. The front will simultaneously be pulled into a developing surface low pressure system over northeast Colorado. Forecast soundings are rather unimpressive in instability, but we may still see some scattered showers and thunderstorms go up along this boundary (probably located from Wheatland to the SW corner of South Dakota). With the latest update, the Storm Prediction Center pulled the Marginal risk back to the north somewhat, which seems reasonable in the drier environment. Expect a fairly windy night across much of the area as the lee cyclone lifts off to the northeast. An unseasonably strong surface pressure gradient will be positioned across the area Sunday evening through Monday morning.

LONG TERM /MONDAY THROUGH SATURDAY/

Issued at 303 PM MDT Sat Jun 27 2026

On Monday, our area will be sandwiched between a powerful upper level low over the northern Rockies and a broad upper level ridge over the southeastern US. An unseasonably tight pressure and height gradient will be present over the area in between these two systems, producing widespread gusty winds. 700-mb height gradients from Craig to Casper reach 73 m by Monday midday per the GFS, which would be high in mid winter, let alone late June. As usual, the GFS is the most aggressive model on the 700-mb winds, but this presents a decent ceiling for wind potential. Expect fairly widespread winds of at least 40 to 55 mph, with some potential (perhaps 30%) for winds to exceed high wind criteria in the typical wind prone areas plus Converse County. Temperatures will be a little cooler Monday across the area, preventing RH from reaching extremely low values. Still, widespread critical fire danger will be favored.

The upper level low will eject to the east by Tuesday, reducing the gradients and thus the wind speeds across our area Tuesday onwards. Expect a gradual warming trend through the week ahead as the broad ridge dominating the eastern two thirds of the country expands westward. Tuesday and Wednesday will probably see temperatures fairly close to seasonable averages, increasing to above average by Thursday and Friday. Winds look marginal for Red Flag Warnings during this period, but it would not be surprising to see wind speeds increase as we get closer. Fire weather concerns will be at least elevated for much of the week. Most afternoons and evenings during the week will bring potential for a few isolated showers and thunderstorms, but it is difficult to determine which days will be most noteworthy, and what the storm hazards might be.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 515 PM MDT Sat Jun 27 2026

Showers and thunderstorms are building across the CWA and may impact the Nebraska terminals at varying times throughout this afternoon. Most of this activity should be winding down by 03Z Sunday. This will be the primary aviation concern for those sites. Elsewhere, gusting winds will continue to impact southeast Wyoming sites for the next several hours as well. Look for the winds to diminish through the evening into the overnight hours across all terminals to generally less than 10 knots by 10Z Sunday. However, this lull in winds will be short-lived as they will ramp up again near the tail end of this TAF period with gusts 20 to 30 knots.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning until 8 PM MDT this evening for WYZ417>419- 430>433. NE...None.