575 FXUS65 KCYS 071107 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 407 AM MST Sun Nov 7 2021 .SHORT TERM...(Today and Monday) Issued at 404 AM MST Sun Nov 7 2021 Mountain wave activity ongoing early this morning across Carbon and Albany Co in Wyoming with southwest flow over the Sierra Madre and Snowy Ranges. WYDOT site along Interstate 80 in the North Snowy Range Foothills (WYZ110) have been consistently gusting 45-55 MPH since around midnight. Arlington has reported the strongest wind gust so far at 65 MPH. 700mb flow around 50 kts will continue until about 15z this morning as mountain wave activity begins to diminish. The current High Wind Warning looks good to continue through midday Sunday, but gusts around 40 MPH are still possible through the afternoon. Did need to expand the Warning to East Platte County with strong downsloping due to mountain wave activity off the North Laramie Range has resulted in strong cross winds along Interstate 25 between Wheatland and Glendo. One more day of warmer weather across the CWA with temperatures rising into the 60s and even 70s over the Nebraska Panhandle ahead of a cold front that will pass through the region late this afternoon and evening. 700mb temps will be around 5C this afternoon before dropping to around 0C Monday. This will result in SFC temperatures being 10-20F degrees cooler Monday afternoon. Only other forecast concern during the short-term period is the chance for precipitation behind tonight's frontal passage. Weak forcing with a passing shortwave will support light showers with a rain/snow mix over east-central Wyoming. Latest hi-res guidance keeps most of the precipitation confined to northern portions of Converse and Niobrara Co., but impactful winter weather is not expected at this time. Kept slight chance PoPs into Monday evening as a secondary shortwave will pass through the area. Euro's precip is a little more widespread with a slightly sharper 500mb height kink, but overall should only support light precip. .LONG TERM...(Tuesday through Saturday) Issued at 404 AM MST Sun Nov 7 2021 No major changes from prior forecast for an active pattern developing next week. Taking a big picture look first, a stronger trough swings through the northern Rockies on Wednesday, shifting our region into a general northwest flow pattern through next weekend. Forecast challenges include some precipitation chances on Wednesday into early Thursday (lingering longer in the mountains), and consistent elevated wind through the weekend. First, a very weak ridge will quickly push through on Tuesday behind the initial shot of cooler air Monday. This is expected to boost temperatures slightly, but come with gusty SW winds especially west of the Laramie range. Guidance is hinting at some mountain wave activity late Tuesday as well, so this continues to warrant close watching. The warming trend will be short lived, as a stronger trough pushes in from the west coast on Wednesday. The nose of a very powerful upper level jet will encroach into Colorado by Wednesday, putting our region in the left exit region, favoring synoptic scale ascent. Models have begun to converge on a scenario showing light to moderate precipitation starting Tuesday night into Wednesday. The forecast reflects the strong westerly with the highest precipitation chances west of the Laramie range and in the mountains where orographic lift can assist. For lower elevations and east of the Laramie range, confidence is lower. Beyond Wednesday, we enter a consistent pattern of NW flow aloft, which may allow mountain snow showers to linger into Friday. More widespread NW winds are possible on Wednesday and Thursday as the trough develops into a strong closed 500-mb low over the northern Plains. Pressure gradients across our region remain tight per model guidance all the way through next weekend, suggesting a likelihood for persistent breezy to windy conditions as the jet core slowly shifts to the east over the CWA in advance of the ridge building into the west coast. Temperatures will be much colder than what we've enjoyed this weekend for the long term period. Wednesday's highs are a little uncertain as the precise timing of the surface cold front will determine if there is time to warm up ahead. Thursday looks like the coldest day of the forecast period, with 700-mb temperatures behind the front plummeting to below -10C. A gradual warming trend will resume on Friday into the weekend. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1134 PM MDT Sat Nov 6 2021 VFR conditions expected through the forecast period. Gusty winds and wind shear remain the main concerns tonight. Elevated winds are expected to continue through the night at KRWL. Elsewhere, stronger winds decoupled from the surface in the lowest 2-3 kft could create wind shear concerns. Winds are expected to increase again during the day on Sunday, especially west of the Laramie range where gusts in the 30-40kt range are possible. && .FIRE WEATHER... Issued at 404 AM MST Sun Nov 7 2021 Elevated fire weather conditions once again Sunday afternoon for extreme southeast Wyoming and the southern Nebraska Panhandle. Afternoon RHs will drop to around 15 percent, but once again winds will remain below critical thresholds. Cooler weather arrives beginning tonight with a passing cold front that will keep fire weather concerns minimal through much of this week. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning until 11 AM MST this morning for WYZ107-110. NE...None. && $$ SHORT TERM...MB LONG TERM...MN AVIATION...MN FIRE WEATHER...MB