Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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821 FXUS65 KCYS 041149 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 549 AM MDT Sat May 4 2024 .KEY MESSAGES... - Mainly dry and warmer conditions are anticipated for the weekend. - Strong winds (60+ mph) return to southeast Wyoming and western Nebraska Monday with a prolonged period of elevated winds continuing for wind prone locations through midweek. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 247 AM MDT Sat May 4 2024 Today...Transitory shortwave ridging aloft will build overhead and with plenty of sunshine and 700 mb temperatures near 2 Celsius, maximum temperatures will reach the upper 50s to mid 60s, with south low level winds limiting the warmup. Tonight...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. Sunday...Southwest flow aloft strengthens ahead of the approaching trough aloft over the Great Basin states, inducing a fairly significant surface trough along Interstate 25. Surface and low level gradients support a windy day with brisk south to southeast winds. Although the atmosphere will be relatively dry, it appears there will be enough low and mid level moisture to support isolated afternoon shower and thunderstorm coverage along the surface trough from Douglas to Laramie. 700 mb temperatures near 8 Celsius support maximum temperatures from the upper 60s to mid 70s. Sunday night...The negatively tilted shortwave trough aloft pivots into western Colorado, sending the leading edge of a potent Pacific origin cold front into our western counties. Looks like enough low and mid level moisture, combined with cold frontal lifting and dynamic forcing associated with the 500-300 mb and 700-500 mb quasigeostrophic forcing to produce scattered showers and isolated thunderstorms across our forecast area, with snow showers becoming widespread across our Snowy and Sierra Madre Ranges. && .LONG TERM /MONDAY THROUGH FRIDAY/... Issued at 247 AM MDT Sat May 4 2024 An upper level low will be traversing the region early next week with the trough axis of the initial wave passing through the CWA Monday. While severe storms are expected across the central plains farther east, strong winds are likely to be the local impact across southeast WY and western NE with this storm system. Strong cross barrier winds developing across the Laramie Range with impressive downward omega fields in the wake of the trough axis passage could lead to wind gusts 70-75 mph along the I-25 corridor. Latest NBM probabilities of 55+ mph wind gusts are quite high (>80%) for most wind-prone areas Monday across southeast WY with areas covered by 50% probabilities expanding outside of wind-prone locations onto adjacent foothills and plains. Additionally, in-house guidance continues to show high probabilities (60-80%) for high winds. There remains to be some uncertainty with the duration of this wind event with elevated to potential high winds continuing through Wednesday morning. However, guidance has been starting to suggest Monday is the most likely timing of the strongest winds across much of the area, while wind-prone locations could continue to see occasional gusts into midweek. 700mb flow climbing over 60 kt across southeast WY with strong ensemble support for high winds early next week as the latest NAEFS and EC are showing over climatological 99th percentile 700mb winds. Precipitation chances Monday will be best across Carbon Co as well as over east-central WY extending northward. Surface cyclogenesis with this upper low track appears more likely in southeast MT and western SD keeping much of the precipitation shield to the north. Additionally, this upper level low looks to stall out across the central CONUS with a potentially retrograding surface low 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 through the remainder of the week. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 541 AM MDT Sat May 4 2024 VFR conditions currently across area terminals with isolated pockets of low clouds developing near southeast WY terminals. Expected mostly clear skies to persist throughout the day with gusty southerly winds around 20-30 kt this afternoon. Gusty winds will continue into this evening across the NE panhandle with a nocturnal LLJ setting up. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...RUBIN LONG TERM...MB AVIATION...MB