textproduct: Cheyenne

KEY MESSAGES

- Dry, warm, and breezy conditions are expected to continue through Thursday, with mild overnight lows.

- Chances for a few showers return Saturday (Halloween) with temperatures remaining mild.

- A pattern change to colder, wetter, and windier conditions is favored Sunday into Tuesday, but the details remain highly uncertain at this time.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 320 PM MDT Wed Oct 28 2026

The shortwave ending up sagging further south than what model guidance was showing yesterday. The cloud cover and showers were slated for Central and Northern portions of Wyoming. The showers ended up cutting right through Southeast Wyoming with thick low level clouds covering the Nebraska Panhandle. Most of the precipitation from these showers ended up being virga so little to no rainfall actually reached the surface. Besides possible fog come Friday morning... the forecast really hasn't changed. 700mb temperatures are really stable around 6C and the upper level ridge is still the dominant weather regime for the next 48 hours. Daily high temperatures are going to remain in the 60's Thursday and Friday with overnight temperatures in the 30's and 40's for a pretty average fall-like couple of days. The vorticity and Warm/Cold air advection are pretty standard and nothing to write home about. So the ridge is really just performing how it should and suppressing any convection over the next couple days.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 320 PM MDT Wed Oct 28 2026

Most of the area will see pleasant conditions for Halloween trick-or- treating this year. Broad ridging will remain over the area this weekend, supporting above average high temperatures ranging from the upper 50s in Carbon and Albany counties to the low to mid 60s over the High Plains. Expect a mix of cloud cover and sunshine as plentiful moisture moves over the area aloft. A weak vort-max passing through the area in the southwest flow overhead will help to support a few afternoon and evening showers, mainly over and near the higher terrain, but the chance for appreciable rainfall or thunder is low. Due to high humidity and cloud cover, overnight low temperatures will be mild for this time of year, only dropping to the upper 30s to lower 40s east of I-25, and mid to upper 30s to the west. Near saturated conditions will produce the potential for some spooky fog to develop both Saturday morning and Saturday night. Sunday looks mild again, but slightly cooler than Saturday with skies becoming mostly cloudy ahead of the next storm system approaching the area.

A complex storm system will push across the western CONUS Sunday into early next week. Two major players will make up this system: first, a strong, moisture-laden upper level low riding the subtropical jet stream into the southwest and second, a potent Pacific trough pushing into the northwest. The primary questions concerning the evolution of this system are if, when, and where the two approaching systems might merge together. Ensembles have shifted slightly over the last 24 hours, but have yet to converge on a solution. Thus, several scenarios still remain, though the probabilities have changed. In the first scenario (approx 40% chance), the two features do not merge at all. Two separate mid- level circulations competing with one other would mean muddy forcing forcing for ascent and limited precipitation potential. We could still expect some rain and snow showers, but amounts would be modest (0.25" or less for Laramie, Cheyenne, Wheatland, Scottsbluff, 0.25" to 0.5" in Rawlins and Chadron). In the second scenario (approx 50% chance), the two systems merge, but this occurs a little too late and a little too far east for a widespread major precipitation event for our area. Still, it would be enough for a moderate rain event over western Nebraska, and some potential for accumulating snow especially for the elevated ridges (Cheyenne Ridge & Pine Ridge). The scenario in which the two systems merge early enough to produce a major event has decreased in probability (to around 10%) as fewer ensembles now show this potential. The ECMWF Extreme Forecast Index for QPF today has decreased slightly as well to around 0.5 to 0.6 over much of the area. This tells us that while an anomalous event is still possible, only a small subset of ensemble members show this, keeping confidence low.

Overall probabilities for 0.5" of liquid precipitation are the lowest around Laramie, Cheyenne, and Wheatland (30-40%). Probabilities increase both east and west, with Rawlins around a 50% chance to exceed 0.5" and the Sidney to Chadron corridor in the 60 to 70% range. In addition to the uncertainty in QPF, there is also uncertainty in the snow levels with very marginal temperatures for snow over much of the area. Cooler air moving in through the event should lead to snow levels starting fairly high (perhaps 9000 ft) and then dropping overnight Sunday night and through the day Monday. The question is how low they can get. Thus, there is fairly good confidence in accumulating snow for the mountains (90+% chance for 1" and 50% chance for 6"), but lower confidence around where most folks live. The best chances for 1" or more of snow outside of the mountains are in the valleys of Carbon and Albany counties, and the elevated ridges of the High Plains.

Regardless of the precipitation outcome, a cold front will sweep through the area Sunday night, bringing colder and windier conditions into the area for Monday. Which of the above scenarios that ends up playing out will also affect the wind direction and potential for high winds. Still, there is high confidence in a windy day along and east of the Laramie range. About 25% of ensemble members have 700-mb winds sufficiently high to support widespread high wind potential, while the I-80 summit area has about a 50% chance for high winds. Look for lingering impacts in the form of cool temperatures and windy conditions on Tuesday, but we should start to lose the wind and warm up slightly by Wednesday.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1100 PM MDT Wed Oct 28 2026

No aviation concerns as VFR conditions will prevail across all terminals for the duration of this TAF period. A few high level clouds are rolling through, they pose no threat, along with winds generally less than 10 knots, varying in direction from southerly to southwesterly.

CYS WATCHES/WARNINGS/ADVISORIES

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