textproduct: Cheyenne

KEY MESSAGES

- Widespread strong to locally damaging winds will continue through the late morning hours across much of the CWA.

- A lack of significant moisture combined with strong winds and near critical relative humidities has prompted a Red Flag Warning for Thursday, and a Fire Weather Watch for Friday.

- Another significant wind event is expected Thursday night into Friday, possibly lingering into early Saturday. Wind gusts possibly exceeding 90 mph are expected once again along portions of the I-25 corridor with widespread 60 to 80 mph gusts elsewhere.

SHORT TERM /THROUGH FRIDAY/

Issued at 305 AM MST Thu Dec 18 2025

The forecast just doesn't get any easier as we continue with the ongoing high wind products across the region, with further wind concerns as we move through the day and into Friday. Through the late morning hours strong winds should persist across most of the eastern half of the CWA alongside our usual windy location of the Arlington area. In fact, this location was our winner of yesterday with a pair of verified wind gusts over 100 MPH! By the late morning hours most locations should see conditions back below high wind criteria, but this will be a brief respite at best.

Accompanying these winds through the morning and afternoon hours will be a critical environment for fire weather conditions. While the overall conditions won't reach our usual criteria for red flag conditions (winds gusts 25+ mph, RH values 15% or less), yesterday proved that very high winds and modest RH values alongside how dry the grasses across the high plains are is more than enough to create a critical environment. Working with our neighbors to the south, we have issued a Red Flag Warning valid starting at 5 AM this morning and continuing through the afternoon hours. Any new fires that do start will spread rapidly.

This evening starts the next round of high winds for the CWA and will continue through late Friday into Saturday morning. At the upper levels, a Pacific trough moving inland will tighten the pressure gradient and bring a stout jet over the CWA yet again. Moving further down, at 700mb the jet will once again intensify with speeds of 90-95+ knots noted on the GFS, and then at the surface Craig to Casper pressure gradients once again in excess of 85-90 meters. Of note, the previous discussion mentioned the inversion at the 650-600mb level being a little higher which might prevent some of the mountain wave breaking we had seen yesterday, but latest analysis of some of the high resolution guidance indicates we may actually see that a little lower near 675 or even 700 mb, which would put us in a similar position for the excessive wind speeds we just saw. In either case, a similar event of widespread gusts 60-80 mph is expected for the CWA, with localized gusts 80-90+ mph expected for our wind prone locations. High wind watches beginning this evening and continuing through Saturday morning have been issued, and as of this writing the plan is to begin upgrading those possibly as early as later this morning.

Once again we are facing another round of critical fire weather conditions on Friday as well, and yet again in tandem with our neighboring office to the south, have issued Fire Weather Watches, this time for a much larger portion of our high plains areas in Wyoming and Nebraska. Portions of this watch may even reach our standard threshold for a Red Flag Warning, but in any case the danger of very high winds alongside low RH values and a lack of notable moisture will fuel further fire weather danger for the area.

Finally, behind the cold front today, temperatures will be closer to what we would expect for December, with highs in the 30's to 40's after widespread sub-freezing lows this morning. But with the ridge getting a quick resurgence on Friday, expect those winter-like temperatures to quickly spike back into the 50's to 60's (which will also fuel our dry conditions as RH values drop in response). Overnight into Saturday morning the next front will approach and move across the region with precipitation chances accompanying it. While some light to occasionally moderate rain, possibly with snow mixing in or transitioning over to, will be possible, not seeing the signal for the stronger bands that produced snow squalls yesterday. For now, holding off on messaging this, but we'll likely see several inches of snow in the mountains with a possible advisory needed, with the lower elevations getting a small hit of moisture, but likely missing much of the region east of I-25.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/

Issued at 430 PM MST Wed Dec 17 2025

A broad ridge will be the dominate pattern for the long term. Friday night into Saturday, An Alberta clipper will move across the US/Canada border compressing the pressure gradient against our broad ridge. This in turn will sustain our 700mb jet into the 60 to 70kts range. Concurrently the global model omega fields are still showing maxed out downward omegas indicative of another high wind event continuing through the overnight period. Our in house algorithm also agrees as it gives a 75 to 80 percent prob of achieving a high wind criteria. The high wind forecast gets a little tricky through the weekend as there is a little bit of timing disagreement with the arrival of the next wave between the global models. To add to the uncertainty, the ensemble cluster analysis depicted about equal chances for the GFS solution of a more progressive system limiting the lull in high winds Saturday into Sunday, and the Euro delayed solution that has the wave arriving about late Sunday night into Monday morning. Behind this wave the 700mb jet looks to be around 55 to 60kts which would be enough to achieve high criteria. So depending on the timing of this wave we could see a lull in high winds Saturday afternoon through Sunday morning. The global omega fields have some downward motion but the 700mb jet isn't portrayed as having sustained winds of 55kts or higher during that time. But to add some confidence in the lull in high winds. Our in-house algorithm shows higher confidence with 40 to 60 percent probs of elevated winds as opposed to winds that meet the high wind criteria. After the open wave moves through the winds on the backside look currently more elevated with the 700mb jet being between 40-55kts. So the winds look to remain gusty through the start of the work week at the very least. Temperatures on the other hand look to remain in the high 50's to low 60's throughout the long term as this ridge is forecasted to remain anchored over the West half of the United States. Overnight temperatures will drop into the high twenties Saturday night making it the coldest night as the rest of the forecasted temperatures look to be in the 30's possibly 40's through Christmas day.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 446 AM MST Thu Dec 18 2025

VFR conditions expected over the next 24 hours. Winds remain the primary hazard as widespread gusts of 30-50 knots persist into this evening for WY terminals, while NE terminals should see a break from winds during the afternoon and evening as winds calm down to around 12-15 knots or less. Winds resume gusting for all terminals by tomorrow morning though, with gusts 25-50 knots by the end of the TAF period, alongside low level wind shear. CIGs expected to be around mid to high levels at FEW to SCT.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning until 11 AM MST this morning for WYZ102- 106>108-110-116>119. Fire Weather Watch from Friday morning through Friday evening for WYZ430>433. Red Flag Warning until 5 PM MST this afternoon for WYZ430-431. High Wind Watch from this evening through late Friday night for WYZ101-107-118. High Wind Watch from late tonight through Friday evening for WYZ102-108-119. High Wind Watch from this evening through late Friday night for WYZ103-105-106-109-113-115-117. High Wind Watch from this afternoon through Saturday morning for WYZ104-110-116. NE...High Wind Warning until 11 AM MST this morning for NEZ002-003- 019>021-054-055-095-096. Fire Weather Watch from Friday morning through Friday evening for NEZ436-437. High Wind Watch from Friday morning through Friday evening for NEZ019-020-054-095-096. Red Flag Warning until 5 PM MST this afternoon for NEZ437.