Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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380 FXUS65 KCYS 011129 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 529 AM MDT Wed May 1 2024 .KEY MESSAGES... - A series of weather disturbances will move across the forecast area Thursday and Friday, producing a chance of showers and thunderstorms mainly during the afternoons and evenings. - Drier and warmer conditions are anticipated for the weekend. && .SHORT TERM /THROUGH THURSDAY NIGHT/... Issued at 305 AM MDT Wed May 1 2024 Current KCYS radar loop early this morning shows isolated rain showers, and a few embedded thundershowers, moving northeast across the area with some light rainfall and mountain snow. This activity is in response to WAA along the stalled frontal boundary across Colorado. High res guidance shows this front lifting northeast slowly as a warm front this morning with increasing coverage of showers and maybe a thunderstorm or two through noon. Further west, another progressive upper level trough will push eastward across the Great Basin Region and into Wyoming later today. Once this trough moves into Wyoming, expect an increase in coverage of thunderstorms this afternoon, mainly east of I-25 as low level instability and upper level jet dynamics result in some low to midlevel forcing across the high plains. Not sure how far west these thunderstorms will develop, but kept POP between 50 to 80 percent for most of the western Nebraska Panhandle and far southeast Wyoming. May see some decent precip amounts with some of this activity into this evening. With SBCAPE around 300 to 600 j/kg and dewpoints struggling to reach 40 degrees this afternoon, not expecting any strong to severe weather at this time. Otherwise, the airmass associated with the upper level trough is notably colder compared to yesterdays disturbance which brought strong winds to the portions of the area. Models continue to show 700mb temperatures lowering between -4c to -8c, which is still several degrees warmer than what models were showing a few days ago. Kept low temperatures tonight near freezing for most areas, and well into the low to mid 20s west of the Laramie Range. Once the cold air arrives tonight...most of the precipitation will likely have already ended across the region with any snow accumulations confined to the mountains. Will not issue any winter headlines for the mountains with snow accumulations below Advisory criteria. For Thursday...similar conditions are expected compared to Tuesday with a bit less wind, but cooler temperatures, as the cold front settled across central and southern Colorado. It should be mostly dry across the area with some shower activity developing over the mountains in the afternoon. Increased high temperatures slightly due to recent model trends and more sunshine forecast through the day. Afternoon highs in the mid to upper 40s west of the Laramie Range expected with 50s to near 60 across the eastern high plains. The next round of precipitation is expected later Thursday night as the stationary front to the south lifts northward as a warm front and another progressive Pacific trough quickly moves eastward across the Great Basin. This evolution is a little different than what previous model runs were suggesting, but increased POP and cloud cover after midnight Thursday into early Friday morning. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Issued at 215 AM MDT Wed May 1 2024 Friday...A secondary shortwave trough aloft is progged to move across our counties near peak heating, and with adequate low and mid level moisture and a cold frontal passage, we anticipate scattered showers and some thunderstorms in the afternoon and evening. Saturday...Warming and drying expected as a transitory low amplitude shortwave ridge aloft builds overhead. 700 mb temperatures near 4 Celsius will yield maximum temperatures in the lower to mid 60s. Sunday...Continued dry as the flow aloft transitions to southwest and there is limited low and mid level moisture. This day looks like the warmest day of the period as a low level thermal ridge develops with 700 mb temperatures near 10 Celsius yielding maximum temperatures mainly in the 70s. Monday...Cooler temperatures expected as the next progressive shortwave trough aloft moves across the region. It looks like there will be adequate low and mid level moisture to produce scattered afternoon and evening showers. Tuesday...Looks like a windy and mild day as a wound up trough aloft and its associated surface low pressure pivots across the Dakotas, producing decent low level pressure gradients for our forecast area. With cyclonic curvature aloft and some low and mid level moisture, we anticipate isolated afternoon showers despite the westerly low level downslope winds. && .AVIATION /12Z TAFS THROUGH 12Z THURSDAY/... Issued at 524 AM MDT Wed May 1 2024 Southwest flow aloft will prevail, with a weather disturbance moving across the terminals today producing some showers. Wyoming TAFS...Ceilings will range from 5000 to 12000 feet. Showers will be in the vicinity of Laramie and Cheyenne from 18Z to 02Z. Winds will gust to 30 knots at Rawlins and Cheyenne from 16Z to 02Z, and to 30 knots at Laramie through the period. Nebraska TAFS...Ceilings will vary from 4000 to 10000 feet. Occasional showers will occur from 19Z to 01Z reducing visibilities to 4 miles. Winds will gust to 30 knots until 01Z. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...TJT LONG TERM...RUBIN AVIATION...RUBIN