textproduct: Cheyenne

KEY MESSAGES

- Near to record warmth expected Wednesday under high pressure aloft. Gusty showers and thunderstorms possible through Wednesday evening.

- Red Flag Warnings have been expanded to include all of western Nebraska and extended through Friday evening.

- High Wind Watches have been upgraded to Warnings for the typical wind prone regions of southeast Wyoming from late Wednesday night through Thursday evening.

- Next chance for precipitation returns during the weekend alongside cooler conditions.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 246 PM MDT Wed May 13 2026

Showers are beginning to pop up west of the Laramie Range early this afternoon. Showers will continue to spread eastward throughout the afternoon into eastern Wyoming and eventually the Nebraska panhandle by this evening. Model soundings show a decent amount of CAPE, so these showers have the potential to produce lightning. Soundings also show a deeply inverted-V profile with extremely dry surface and low-level. DCAPE values across the CWA are 1500 J/kg and greater, leading to the threat of dry microbursts. Wind gusts in excess of 70 MPH cannot be ruled out. Also, little if any precipitation will actually make it to the ground, leading to dry lightning concerns. Hi-Res guidance has a few isolated showers/storms continuing overnight as an upper- level trough begins to pass north of the CWA. Showers will likely be out of the area by Thursday morning.

As the aforementioned trough swings to the north, MSLP gradient along and west of the Laramie Range will tighten early Thursday morning. 850 and 700 mb CAG to CPR height gradients will also increase with the trough to the north, raising values up to almost 60 meters. As a result, winds aloft will respond, reaching 55 to 60 kts over the wind prones. Subsidence will be decent and will help with aiding these winds down to the surface. Upgraded the High Wind Watches in effect for the wind prones to Warnings with this forecast package. The GFS has consistently been showing this signal and in-house guidance shows a 40 to 60 percent chance of high winds occurring in the typical southeast Wyoming wind prone areas. High winds are most likely to occur between 6 AM and 3 PM on Thursday with wind gusts between 55 and 65 MPH.

Outside of the wind prones, Thursday is still expected to be a very windy day as the trough passes to the north. The predominately westerly winds will add to the already dry airmass in place. With downslope winds helping to contribute to widespread relative humidity values in the single digits. Wind gusts in excess of 45 MPH will lead to widespread critical fire weather. A Red Flag Warning is in effect for the Nebraska panhandle through Friday evening. Vegetation in southeast Wyoming is in green up which limits some of the fire weather concerns, however did put out a Special Weather Statement for Wyoming through Friday evening to highlight the increased fire danger as critical conditions will be present. Friday will be almost a repeat of Thursday but with slightly weaker winds. With the trough out of the area on Friday, a zonal flow pattern will be in place which still favors windy conditions. Wind gusts over 35 MPH will still be possible for much of the CWA on Friday with relative humidity values still stuck in the single digits for a large portion of the area. As such, fire weather concerns will continue through the day Friday.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 246 PM MDT Wed May 13 2026

A wet and unsettled pattern is taking shape for the the long term period for southeast Wyoming and western Nebraska. This pattern will be largely driven by an approaching trough embedded in westerly flow over the northwest CONUS. This trough will move inland on Saturday and pass through the region on Sunday, bringing lowering heights and a plume of pacific moisture aloft over the higher terrain. After a mild day on Saturday with a high likelihood (over 75% chance) of above average temperatures throughout the high plains, a the surface frontal boundary is expected to drop south through the northern high plains. This boundary will reach east-central Wyoming by daybreak on Sunday and push south throughout the day, bringing easterly upslope flow and overcast skies as well as a cooldown in temperatures. While isolated showers will be possible on Saturday afternoon and evening in a deeply mixed, prefrontal airmass, Sunday appears to bring high confidence of area-wide light to moderate rainfall, especially in the favored easterly upslope regions of the Cheyenne Ridge and Laramie Ranges. Currently, the ECMWF ensemble is a bit wetter than most NAEFS members, supporting perhaps up to an inch of rain in the south Laramie Range into the Cheyenne Ridge from Sunday through Sunday night. Confidence remains only moderate for these heavier rainfall amounts, as subtle differences in ensemble clustering suggest some of the deeper upslope moisture may sneak a bit too far south into the Colorado front range and leave eastern Wyoming slightly drier.

From Monday onward, models begin to diverge as GEFS members quickly push this system eastward transitioning us into a drier pattern, whereas ECMWF ensemble guidance generally supports a developing mid-level low over western Wyoming and continued rainfall over much of the state as well as western Nebraska on Monday. Given the post-frontal airmass in place and generally suppressed jet pattern we have been in lately, the instinct currently is to favor the slightly wetter pattern for early next week. Higher confidence exists in continued near-average temperatures, with any days of particularly heavy rainfall likely resulting in lower than average weather. As far as snow for our late-season winter enthusiasts, chances are looking increasingly likely for a snowfall refresh in the higher terrain. Most ensemble guidance keeps mid and upper-level temperatures cooler through early next week, resulting in lower snowfall levels in the Snowy Range, Sierra Madres, and even Laramie Range by Mon-Tues. Up to a foot or more of late-season snowfall is being suggested by at least 30% of ensemble guidance from the Sunday-Tuesday timeframe, especially at elevations above 10kft. We will have to see if this trend continues in guidance but confidence is certainly growing in another late- season snowpack boost.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 555 PM MDT Wed May 13 2026

VFR conditions expected over the next 24 hours. Passing showers/weak storms expected over the next few hours, however ingredients are present to produce strong and gusty outflows with any local storms which will be erratic and variable. Cloud decks with this activity though will remain mid level at lowest, with widespread CIGs becoming either clear or high based overnight into tomorrow. Winds outside of precipitation will be breezy to light through the nighttime hours, but will begin to pick up tomorrow morning as a strong pressure gradient settles in over the region bringing strong gusts of 30-50 knots. Wind shear is also expected to impact Nebraska sites during the overnight and early morning hours before surface winds increase.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning from 6 AM to 6 PM MDT Thursday for WYZ106- 116. High Wind Warning from 3 AM to 6 PM MDT Thursday for WYZ110. NE...Red Flag Warning until 7 PM MDT Friday for NEZ434>437.