Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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133 FXUS65 KCYS 081131 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 531 AM MDT Sat Jun 8 2024 .KEY MESSAGES... - Scattered to numerous showers and thunderstorms are expected over the next 24 to 36 hours. A fast moving complex of storms may impact the I-80 corridor late this morning through early afternoon between Cheyenne and Sidney. Gusty winds are the primary concern, although some small to marginally severe hail also cannot be ruled out. - Monday and Tuesday will see the greatest coverage of late day showers and thunderstorms, while Wednesday and Thursday will be warmer with a general decrease in shower and thunderstorm coverage. Showers and thunderstorms look to return again for Friday. && .SHORT TERM /THROUGH SUNDAY/... Issued at 348 AM MDT Sat Jun 8 2024 An active day ahead for a large portion of southeast Wyoming and the western Nebraska Panhandle as a fast-moving mid level short- wave tracks along the Wyoming-Colorado state line. Showers and a few thunderstorms are ongoing across much of the area early this morning, mainly driven by a broad zone of WAA aloft. Latest high res/CAM guidance suggests a second round of activity, initiating in the vicinity of the central/southern Range by mid to late AM, and moving rapidly eastward along the I-80 corridor through mid/ late afternoon. There are still some questions regarding overall storm intensity as early morning convection and low clouds could impact potential destabilization ahead of the second round. Even so, a small window of opportunity could exist for sufficient SFC heating to yield 500-100 J/kg CAPE across far southeast WY & the southern Nebraska Panhandle, roughly along/s of a line from EAN- IBM. Deep westerly flow aloft should support upwards of 45 knots of deep layer vertical shear w/ the orientation favoring chances for organized/bowing line segments capable of producing elevated wind gusts near severe limits. Forecast soundings suggest a deep moist layer and resultant tall/skinny CAPE profiles, a potential limiting factor to the overall hail risk although small hail may still occur with the strongest cores. Scattered showers & storms will persist through Sunday on the northeastern periphery of the building upper-level ridge. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Issued at 348 AM MDT Sat Jun 8 2024 Sunday night/Monday...As daytime heating wanes, isolated to widely scattered showers and thunderstorms will end from west to east overnight Sunday night. West northwest flow aloft develops on Monday, and with plenty of low and mid level moisture available, scattered late day showers and thunderstorms will be on tap again. Temperatures will be warmer than Sunday with less cloud cover. Tuesday...Northwest flow aloft remains, though with increasing heights aloft along with warmer temperatures, and a decrease in low and mid level moisture, we should see less coverage of late day showers and thunderstorms. Slightly warmer with more sunshine expected. Wednesday...Even warmer as the flow aloft turns westerly, and with 700 mb temperatures near 17 Celsius, maximum temperatures will be in the mid 80s to lower 90s. Warmer temperatures aloft will increase the convective inhibition, and with less low and mid level moisture around, it looks like it will be dry. Thursday...Similar synoptic pattern as on Wednesday, though low level winds will become northeast, and with an increase in low and mid level moisture, we expect to see isolated to widely scattered late day showers and thunderstorms. Perhaps a few degrees cooler than Wednesday with upslope winds and more cloud cover. Friday...Ridging aloft, over our forecast area, begins to break down as the next shortwave trough aloft approaches, and with surface lee trough convergence and an increase in atmospheric moisture, we expect scattered late day showers and thunderstorms. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 520 AM MDT Sat Jun 8 2024 A cold front and weather disturbance will combine with adequate atmospheric moisture to produce scattered to numerous showers and thunderstorms this afternoon and evening mainly south of a Rawlins to Scottsbluff line. Wyoming TAFS...Ceilings will range from 6000 to 12000 feet at the terminals, with areas of fog reducing visibilities to 2 miles and ceilings to 1500 feet at Cheyenne after 09Z. Occasional thunderstorms or thunderstorms in the vicinity will occur at the terminals from 17Z to 02Z. Winds will gust to 25 knots at Rawlins until 02Z, to 25 knots at Laramie and Cheyenne from 17Z to 02Z. Nebraska TAFS...Ceilings will range from 5000 to 10000 feet, with areas of fog reducing visibilities to 2 miles and ceilings to 1500 feet after 06Z. Occasional thunderstorms, or thunderstorms in the vicinity will occur at Alliance, Scottsbluff and Sidney from 18Z to 03Z. Winds will gust to 22 knots at Scottsbluff and Sidney from 17Z to 03Z. && .HYDROLOGY... Issued at 254 PM MDT Fri Jun 7 2024 Above normal temperatures have resulted in accelerated mountain snowmelt across the Rocky Mountains this week. Temperatures in the Snowy and Sierra Madre Ranges are expected to remain elevated this weekend, even as a cold front stalls across the mountains. Flood warnings for snowmelt continue for the Little Laramie River west of Laramie, and the Encampment River south of Saratoga, mainly due to minor flooding concerns. Emergency Managers have reported some flooding in these areas today. Flood Watches continue for the upper North Platte River valley and Medicine Bow River near Elk Mountain for potential impacts this weekend. Current forecasts suggests river levels will peak later this weekend and remain elevated into early next week due to some slightly cooler air. However, rainfall in and around the mountains may become an issue this weekend and could lead to rapid additional rises in creeks and rivers. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...CLH LONG TERM...RUBIN AVIATION...RUBIN HYDROLOGY...WFOCYS