textproduct: Cheyenne

KEY MESSAGES

- The long duration wind event continues, with wind gusts expected to peak today. While some breaks or lulls will occur, high winds will be a concern every day through Saturday. - Damaging winds are expected near and in the lee of southeast Wyoming mountain ranges through Tuesday afternoon. Gusts up to 90 mph are expected. - Cheyenne, Laramie, Rawlins, Wheatland, and Douglas can expect wind gusts up to 75 mph through the day today.

- Wind gusts up to 65 mph are expected to spread into High Plains mid morning into the afternoon.

- A cold front will bring a banded rain and snow showers late this afternoon through the evening. This will also bring a brief reprieve from the wind into Wednesday morning.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 415 AM MST Tue Dec 9 2025

Current GOES satellite imagery shows plentiful mid to upper level cloud cover racing inland across the northwest CONUS towards our area this morning. The powerful 150 knot jet streak aloft is nosing into our area this morning, supporting the ongoing high wind event. A strong upper level shortwave is riding along the north side of the jet streak, but has developed a potent lee cyclone over the Canadian Prairie. A surface trough trails south of this feature down to our area, which is dropping surface pressure over our plains and enhancing the MSLP gradient across the barrier. We have already been seeing gusts to around 75 mph in the typical wind prone areas so far this morning, but it is really just beginning. Gradients are expected to continue to climb through the morning, maximizing between about 9AM and noon or so. The plentiful cloud cover moving in makes it a little difficult to ascertain how much mountain wave activity is ongoing via satellite imagery, but forecast models continue to show a stable inversion layer developing around the mountain top height this morning. This should promote increasing mountain wave activity and wave breaking into the early afternoon hours. These breaking waves will be what will be needed to realize the 80 to 95 mph gust potential from this event. Overall, the event looks on track. As we head into the late morning and afternoon hours, 50 to 60 knot winds at 700-mb will spread over the High Plains. Forecast soundings show fairly well mixed boundary layers developing for a few hours during the afternoon, which should help mix these winds down to the surface and get the strong winds spreading into the Nebraska panhandle.

The temporary reprieve from the wind is also still on track for this evening. The aforementioned upper level shortwave trough will race eastward this afternoon. Behind it, surface high pressure will fill in over the plains just in the lee of the Rockies. The front will reach our northernmost forecast zones by mid afternoon (a slight acceleration from previous forecast packages), reaching Cheyenne around 8PM or so. Once pressure starts rapidly rising over the plains, we should see a rapid drop off in the high winds across the area. That's not to say it will be calm, as the front will be accompanied by 35 to 50 mph northwest wind gusts, but the potential for 60+ mph winds will likely decrease behind the initial gusts along the front. We might have a gap even in the wind prone areas beginning around midnight. In addition to the break from the wind, this front will bring a brief window of lift and increased moisture content. Expect to see some banded rain and snow showers developing north of the North Platte River valley between 2PM and 5PM, then spreading south to the I-80 corridor this evening. Neither the lift nor the moisture looks impressive by any means though, so forecast precipitation totals are modest at best. That being said, these are expected to organize into a banded structure along a temperature gradient, so there is the possibility for quick visibility reductions. Temperatures will be shockingly warm ahead of this, such that most of the activity could be rain. However, confidence in remaining all rain is not very high, and this is worth a discussion since a flip to snow could certainly cause travel problems. In the mountains, moist orographic lift will resume midday today, and continue into Wednesday morning. The higher peaks could pick up several more inches of snow accumulation, so a Winter Weather Advisory has been issued.

The surface high will translate across the area into Wednesday morning. By around sunrise though, expect to see surface pressure falling once again right along the crest of the Laramie Range. Wind speeds will pick up again first in Carbon and Albany counties, and then gradually spread eastward through the afternoon. This time, the surface trough is not expected to advance much further east than I- 25, which should confine the second phase of this high wind threat to southeast Wyoming along and west of I-25. Pressure and height gradients will be impressive once again, but probably won't get quite as high as they are expected to today. Therefore, the wind gust potential during phase two Wednesday afternoon and Wednesday night is not quite as high, but still at least a middle tier high wind event for our area. Currently, we are looking at another round of 70 to 80 mph gusts for the wind prone areas, and 60 to 70 mph gusts spreading into the adjacent zones. This will continue into Wednesday night and possibly Thursday. With this forecast package, the High Wind Watch for the remaining wind prone areas was upgraded to a warning and extended out through Thursday night. The other watches in southeast Wyoming were left as is with this update, mainly due to uncertainty in the end time of this phase of the event. Since we are still 30 hours or more away from the start of phase 2, we can let the watch continue for another cycle to get some better precision on the end time.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 415 AM MST Tue Dec 9 2025

Active northwest flow will continue into the upcoming weekend, creating forecast headaches all through the period. Expect the upper level ridge to amplify on Thursday, nudging the baroclinic zone and associated stationary front off to our northeast. Mild temperatures will flood into the area south of the boundary. Another shortwave trough aloft will pass north of the area sometime Thursday or Thursday night, and this will be followed by a surface high, wind shift, and cold front. This should nudge the stalled frontal boundary back to the southwest into Friday morning. Ensembles have come into better agreement keeping most of the frontogenesis off to our northeast Thursday night and Friday, but PoPs still creep into our northern and eastern zones. The front will also do the same thing as tonight's front and pause the high wind threat temporarily. Unfortunately, model guidance has recently been trending more aggressive with winds Friday into early Saturday as the ridge fluctuates overhead once again. While forecast uncertainty remains considerable during this period due to our proximity to the arctic front, it is looking more likely that we may have to tack on another day or two to this very long streak of high winds.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 441 AM MST Tue Dec 9 2025

Very strong winds will impact aviation through the forecast period. This morning, expect significant LLWS at all terminals. Wyoming terminals are already seeing gusts approaching 50 knots, which will continue through much of the day. Gusts may exceed 60 knots mid morning into the early afternoon. In Nebraska, gusts will gradually increase this morning with potential for gusts between 40 and 50 knots between about noon and sunset.

A cold front will sweep southward beginning with CDR around 21z and reaching CYS and LAR last 03z. Expect to see winds shift to the northwest behind this boundary. In addition, scattered banded rain and snow showers will be possible along and for about 2-3 hours after the frontal passage. Brief IFR could occur especially at RWL and LAR where precip type is more likely to be snow. In Nebraska, rain is the more likely precip type, but a quick shot of snow cannot be ruled out. Most terminals should get a break from the wind after midnight.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning until 8 PM MST this evening for WYZ101-102- 104-105-108-109-119. High Wind Watch from Wednesday morning through Thursday morning for WYZ101-107-118. High Wind Warning until midnight MST tonight for WYZ103-106- 107-113>115-117-118. High Wind Watch from late tonight through late Wednesday night for WYZ104-109. High Wind Watch from Wednesday morning through Thursday morning for WYZ105-113-115. High Wind Warning from 9 AM Wednesday to midnight MST Thursday night for WYZ106-117. High Wind Warning until 5 AM MST Friday for WYZ110-116. NE...High Wind Warning until 8 PM MST this evening for NEZ002-003- 019>021-054-055-095-096.