Area Forecast Discussion
Issued by NWS Cheyenne, WY
Issued by NWS Cheyenne, WY
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235 FXUS65 KCYS 152329 AFDCYS Area Forecast Discussion National Weather Service Cheyenne WY 529 PM MDT Thu Aug 15 2024 .KEY MESSAGES... - Fire weather concerns begin to increase Friday as well as Saturday with warmer temperatures and low afternoon humidity. - Seasonable temperatures will continue through the period. Showers and thunderstorms will be most likely on Sunday and Monday, with less coverage for Tuesday and Wednesday. && .SHORT TERM /THROUGH SATURDAY/... Issued at 335 PM MDT Thu Aug 15 2024 Short range models and ensembles all show relatively quiet weather over the next 48 hours as a mid to upper level ridge axis strengthen over the Front Range into this upcoming weekend. One more coolish afternoon today with highs generally in the upper 70s to mid 80s across the area, warmest over the eastern plains. Models show the upper level ridge amplifying over the region on Friday with 700mb temperatures climbing above 15c. Expect high temperatures back into the upper 80s to upper 90s (warmest over far eastern Wyoming and western Nebraska) Friday afternoon with slightly warmer high temperatures Saturday afternoon. Coverage of showers and thunderstorms will be much less compared to the last several days as a drier airmass and increasing midlevel subsidence, both associated with the upper level ridge, move into the area. For today (Thursday), can`t rule out some sub-severe thunderstorms or rain showers late this afternoon through most of tonight. High res guidance has been persistent today in showing some activity lingering past midnight through 300 am local time. Forcing is limited, but model soundings do show slightly low-midlevel warm air advection near the top of the residual boundary layer along with a weak shortwave slowly ejecting east out of the area. This should provide enough elevated CAPE to initiate scattered rain showers and a few thunderstorms through the night...mainly along and south of the North Platte River Valley. With a relatively dry boundary layer, especially further west, can`t rule out some brief wind gusts of 50 mph. Precipitation chances will decrease on Friday as the ridge axis amplifies northward and a drier airmass moves into Wyoming. A dry-line like feature is forecast to develop along the Laramie Range and move eastward through the afternoon. Ahead of this dry-line, expect another round of showers and thunderstorms to develop with a few stronger storms possible. However, coverage should be limited to isolated or widely scattered at best...so kept POP between 15 to 25 percent Friday afternoon east of the Interstate 25 corridor. This drier airmass will remain over the whole forecast area on Saturday with the potential for thunderstorms less than 5 percent through Saturday evening. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Issued at 218 PM MDT Thu Aug 15 2024 The main concern with this forecast is how dry things will become under the influence of the upper level ridge next week. The models and ensembles continue to advertise the upper level ridge staying planted over the Rockies through the end of next week. The big question will be the timing of the subtle shortwaves riding over the ridge. The models/ensembles are showing deeper moisture over the Rockies Sunday and Monday with the highest precipitable water values ranging 0.8 to to 1 inch especially east of the Laramie Range where the heavy rain potential could be a factor. The models are also advertising a chance of seeing strong to severe storms especially over the Nebraska panhandle where the models are advertising dewpoints to be in the 55 to 60 degree range with moderate bulk shear of 30 to 40kts. Tuesday and Wednesday the WPC clusters are favoring the upper level ridge axis building over the Wyoming which will tend to suppress convection and keep the bulk of the deeper moisture east of the forecast area. As a result, temperatures will most likely be a bit warmer on both of these days. Late next week the ensembles/operational models showing the upper level ridge tilting towards the east which may allow for the return of monsoonal moisture back into the area and bring gusty winds into Carbon and Albany counties. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 528 PM MDT Thu Aug 15 2024 Scattered showers are possible across the area this evening and through early Friday morning. Minimal impacts are expected with these showers, however, a few stronger wind gusts will be possible. Otherwise, light winds with mid to high level clouds are expected overnight. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Fire Weather Watch from Friday afternoon through Friday evening for WYZ420>423-425-427-428. NE...None. && $$ SHORT TERM...TJT LONG TERM...REC AVIATION...SF