textproduct: Cheyenne

KEY MESSAGES

- Above average temperatures and chances for gusty showers and some isolated storms today.

- A pattern change will bring a gradual cool down and increased chances for precipitation this week. Moderate to heavy rainfall possible Tuesday night through Wednesday night with some mountain snow expected.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 200 PM MDT Sun Oct 11 2026

We've had a nice bit of clearing today, achieving a bit more sunshine overall than expected. We'll see how this impacts our instability over the next couple of hours with the strongest conditions expected around 6-7 PM helping to fuel thunderstorm potential and even an isolated stronger storm or two. Any storms that do occur, as well precipitation in the form of showers further east, will all have the potential for gusty and erratic winds, possibly nearing severe levels. For the moisture expected from this, while this activity is fueled by the remnants of Tropical Storm Rachel moving across the region, the best forcing will be just to our west. That's not to say we won't see fair amounts of moisture, as PWAT values this evening will be between 0.6-0.9 inch, roughly 200% of normal for this time of year. Meanwhile on the note of strong winds, the High Wind Watch has been upgraded to a Warning for Carbon County as pressure gradients continue to tighten in response to the approaching system. The jet streak is expected to be strongest between 6 PM - 3 AM, but the potential for strong gusts will exist from 3 PM through 6 AM. In house guidance is still not fully convinced with only around a 40% probability for gusts exceeding 58 mph, but high resolution guidance shows 50-60 knot winds at 700mb, and with how windy Carbon County likes to be, a Warning seemed all but necessary.

Precipitation will mostly depart by the morning hours alongside winds weakening, though some lingering showers in Carbon County can't be ruled out. It will be a fair day with temperatures around 2 to 5 degrees lower than Sunday, still several degrees above normal though. While the day will start out pleasant, a deep Pacific Low will begin swinging eastwards and will not only bring a notable cool down, but also begin to increase our precipitation across the region once again. Showers should start to overspread late in the day and overnight, but convective parameters will be meager, so expect mostly rain with an occasional rumble of thunder. Finally as we move overnight into Tuesday, temperatures will finally begin to drop, with the mountains nearing freezing and most lower to mid elevation locations in the 40's to upper 30's. Fall is finally trying to show up as we move into the long term.

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 200 PM MDT Sun Oct 11 2026

A big pattern change is still on track for mid to late week as an amplified ridge over the Intermountain West is replaced by a digging trough and closed low. After spending a couple days over the Pac NW and Great Basin, the low rounds the Four Corners region and emerges onto the Plains near the WY/NE/CO point Wednesday into Thursday. A 100+ kt H3 jet streak, a stout mid-level shortwave, and a surface cool front all precede the low's passage. With moisture streaming northeastward throughout this process, widespread precipitation and much cooler temperatures are in order.

Tuesday... Considerable mid-upper level moisture will be in place as the core of the jet passes nearby, and east/southeast H85 flow helps with orographic forcing. Temperatures should hold warm enough (plains/valleys highs around 60F) and snow levels high enough (10kft) to result in rain as the dominant p-type throughout the day. In fact, relatively steep mid-level lapse rates and marginal MUCAPE across southern WY may be sufficient for a few rumbles of thunder.

Wednesday... The H5 low is knocking on our doorstep as the H7 0C therm presses east across WY. Near surface flow takes on a more northeasterly direction, and forcing strengthens at multiple levels. The NBM envelope has trended cooler considerably, now suggesting 40s for highs in WY and lower 50s for NE. Forecast snow levels drop below 9kft by the evening time, squarely placing the Sierra Madres and Snowy Range in the winter regime. At this time, snow totals appear to hold right near advisory criteria for the higher peaks. Will need to monitor any further cooling trend as the event draws nearer however, if snow levels drop or more time is spent in the dendritic growth zone. Rainfall outside the ranges could be significant as well, with some locations approaching 1" of moisture. Wed night may necessitate frost/freeze headlines, especially for WY and northern panhandle zones. The median of the NBM envelope suggests upper 20s west for most of Carbon and Albany Cos, lower/mid 30s for I-25 corridor and into Sioux Co.

Thursday... Precip tapers across the forecast area, but winds really pick up as north/northwest flow fully takes over. 30+ kts flow at H5- 7 should easily translate to the surface via mechanical mixing, and height gradients surpass 30m across WY/CO. Temperatures attempt to rebound with gradual clearing through the day, with highs generally in the 50s (WY) and lower 60s (NE).

Friday and beyond... The upper ridge rebuilds over the Western US, and a broad surface high settles onto the Great Plains. Seasonably mild and dry conditions come right back next weekend, with highs in the 70s near/east of I-25 for Saturday and Sunday.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1131 AM MDT Sun Oct 11 2026

Wind will be the primary aviation weather concern through the forecast period as rain showers move through this afternoon and evening, followed by a strong lower jet. Gusty erratic winds are anticipated in/near any shower for the WY terminals (mainly RWL and LAR), with speeds possibly approaching 50 kts. Low level wind shear is then likely overnight for most terminals. Meanwhile, an area of stratus Monday morning could bring MVFR ceilings from RWL to CDR.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning until 6 AM MDT Monday for WYZ104-109>111. NE...None.