Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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487 FXUS65 KCYS 031143 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 543 AM MDT Fri May 3 2024 .KEY MESSAGES... - A cold front will move through the region today with another round of shower activity in the mountains and isolated thunderstorms over the southern Nebraska Panhandle. Snow levels will remain above 6500 feet. - Mainly dry and warmer conditions are anticipated for the weekend. - Breezy to windy, and cooler weather expected for Monday through Wednesday, with isolated to scattered late day showers and thunderstorms. && .SHORT TERM /THROUGH SATURDAY NIGHT/... Issued at 305 AM MDT Fri May 3 2024 Today...A progressive and positively tilted shortwave trough aloft moves from western Wyoming this morning to central Wyoming by mid afternoon and to eastern Wyoming by late afternoon. Its associated fairly strong cold front moves quickly across our counties by late afternoon with winds turning to the north and increasing. With ample low and mid level moisture, and decent frontal lift along with dynamic lift supported by 500-300 mb and 700-500 mb quasigeostrophic lift, we anticipate scattered to numerous showers spreading from our western counties this morning to our southern and eastern counties this afternoon, along with isolated thunderstorms mainly east of I- 25. Snow will fall over the higher elevations of the Snowy and Sierra Madre Ranges with amounts from 4 to 7 inches, however with the snow falling during the daylight hours, there will likely be some melting and compacting of the snow, thus no advisory issuance seems necessary. With the strength of the cold front and the blustery north winds, it will feel rather chilly for early May. Tonight...Precipitation will end quickly this evening as the shortwave trough aloft moves off to our east. Looks like a cold overnight as surface high pressure builds southward across eastern Wyoming and western Nebraska and skies become clear. Saturday...Transitory shortwave ridging aloft will build overhead and with plenty of sunshine and 700 mb temperatures near 2 Celsius, maximum temperatures will reach the mid 50s to mid 60s, with southeast low level winds limiting the warmup. Saturday night...Decent moderation in temperatures will occur as southwest flow aloft strengthens ahead of the approaching trough aloft over the Great Basin states, inducing increasing south winds and a thermal ridge over our counties, with low temperatures from the mid 30s to lower 40s. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Issued at 305 AM MDT Fri May 3 2024 Sunday will be the warmest day of the weekend as a shortwave ridge axis moves just to the east ahead of a large scale upper level low moving towards the central Rockies. 700mb temps will warm near 6-10C with afternoon temperatures reaching the upper-60s and 70s ahead of increasing cloud cover with the approaching upper level low. Areas west of the Laramie Range, especially southwest Carbon Co and the Sierra Madres will begin to see increasing moisture Sunday night leading to accumulating snowfall above 7500 ft elevation. Based on the upper level low track, the majority of wrap around moisture will most likely develop farther north and east. However, lee troughing across much of the WY Front Range will lead to increasing mslp gradients and the potential for strong westerly winds across our area starting Monday. Latest NBM probabilities of 55+ mph wind gusts are quite high (>80%) for most wind-prone areas across southeast WY with areas covered by 50% probabilities expanding outside of wind-prone locations onto adjacent foothills and plains. Additionally, in-house guidance has been showing high probabilities (60-80%) for high winds, however there still remains run-to-run uncertainty with the duration and timing of strongest winds. This should clear up as models continue to get a better idea on the low track and evolution. Right now, the timing for the strongest winds appears to be Monday afternoon with 700mb flow climbing over 60 kt across southeast WY and 850mb (700mb) CAG-CPR height gradients exceed 70m (60m). Latest cluster analysis shows ~45% of EC membership favors a slightly farther south track that will lean towards stronger wind speeds aloft over our area. Overall, there remains strong ensemble support for high winds early next week with latest NAEFS and EC showing over climatological 99th percentile 700mb winds. This upper level low looks to stall out across the central CONUS leaving southeast WY and western NE under a general troughing pattern through the remainder of the week. This will lead to below average temperatures for early May with additional chances for light precipitation. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 536 AM MDT Fri May 3 2024 SCT-BKN mid-level clouds persist early this morning across the region with VFR conditions as rain/snow showers approach from the west per latest satellite and radar imagery. These showers will likely reach KRWL over the next few hours with lowering ceilings and visibilities through the morning. Additional shower development is expected along a frontal boundary that will be positioned from KLAR through KCDR by midday with gusty northerly winds developing as the front continues to move to the south. Cannot rule out a few rumbles of thunder near KSNY which could see a stronger storm develop early this afternoon before the frontal boundary clears the area. Skies will begin to clear early this evening as precipitation continues to move off towards the east. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...RUBIN LONG TERM...MB AVIATION...MB