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Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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066 FXUS65 KCYS 160839 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 239 AM MDT Fri Aug 16 2024 .KEY MESSAGES... - Critical fire weather conditions expected this afternoon and possibly Saturday as high pressure builds over central Wyoming. - A few severe thunderstorms possible this afternoon across eastern zones where moisture will be better for storm development. - Seasonable temperatures will continue through the period. Showers and thunderstorms will be most likely on Monday, Wednesday and Thursday, with less coverage for Tuesday. && .SHORT TERM /THROUGH SUNDAY/... Issued at 238 AM MDT Fri Aug 16 2024 Two areas of surface high pressure analyzed across the Rockies this morning. First over northern and northeast Wyoming and a second area of high pressure over north central Colorado up to near Laramie. These two high pressure areas separated by a surface trough that lays roughly from Rawlins to Douglas to Cheyenne this morning. Dewpoints in the mid 50s east of this surface trough in the Nebraska Panhandle. Storms have formed along and east of this trough this past evening and continue to slowly weaken over the southern Panhandle as of 2 AM. Across central Wyoming...an upper level ridge continues and will slowly shift eastward through the morning hours. Very dry air west of the ridge axis will filter into Carbon and Albany Counties through the morning hours. Guidance showing Tds in the low 20s to upper 20s across Carbon and Albany Counties after 18Z today. GFS 700mb winds still forecast to increase to 30-35kts behind the ridge axis. Decided to upgrade the Fire Weather Watch to a Red Flag Warning from noon to 8PM today. Further to the east...dewpoints remain high across the Panhandle. Our forecast for this afternoon showing low to mid 50s across much of the Panhandle with low to mid 30s along the I-25 Corridor. Looks like possibility of an upper shortwave working through the upper ridge this afternoon. Mixed signals as NAM MUCAPE up around 2000J/KG over the southern panhandle this afternoon. GFS on the other hand...showing MUCAPE around 400-500J/KG. Earlier HRRR simulated radar was showing a strong to severe cell up by Chadron and possibly Alliance...but has since backed off on that development. Given the uncertainty in the various models...decided to stick pretty close to SPC`s Marginal Risk area for this afternoon. Saturday looks mainly dry across the CWA as we stay under the upper ridge axis. But GFS suggesting an increase in monsoonal moisture from the southwest moving into Carbon/Albany Counties on the west side of that ridge Saturday night into Sunday. ANother fairly strong shortwave moves into the west side of this ridge Sunday afternoon. ECMWF/SREF in good agreement on increasing PoPs for Sunday as PWATS climb to 1.3 inches in the Panhandle and near an inch here at Cheyenne. Could see heavy rainfall returning to some areas Sunday afternoon. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Issued at 238 AM MDT Fri Aug 16 2024 Sunday night/Monday/Tuesday...Atmospheric moisture content remains about the same for Monday, with a decrease on Tuesday. Despite ridging aloft, we still anticipate scattered to numerous showers and scattered thunderstorms on Monday, most numerous near the Colorado state line, with a significant decrease in coverage for Tuesday. Maximum temperatures will be slightly warmer for Tuesday with 700 mb temperatures near 17 Celsius. Wednesday...Although ridging aloft continues, precipitable water values remain nearly the same as Tuesday, ranging from 0.8 to 1.1 inches. Thus, it looks like widely scattered to scattered late day showers and thunderstorms again, most numerous near the Colorado state line and west of a Douglas to Kimball line. 700 mb temperatures remain near 19 Celsius, yielding maximum temperatures from the mid 80s to upper 90s. Thursday...The ridge axis aloft moves further east over the Central Plains states, with an increase in atmospheric moisture for our counties, thus providing more fuel for scattered afternoon and evening showers and thunderstorms, most numerous near the Colorado state line. With more cloud and precipitation coverage, temperatures will be slightly cooler. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 945 PM MDT Thu Aug 15 2024 Scattered showers and thunderstorms will continue overnight and into the early morning hours. Minimal impacts are expected with these storms, but brief light to moderate rain and gusty winds are possible. Winds pick up a bit during the day Friday, with diurnal wind gusts of 20 to 25 kts likely. An isolated storm or two will be possible during the afternoon, mainly in the Nebraska panhandle. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Red Flag Warning from noon today to 8 PM MDT this evening for WYZ420>423-425-427-428. NE...None. && $$ SHORT TERM...GCC LONG TERM...RUBIN AVIATION...SF