Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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206 FXUS65 KRIW 261006 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 406 AM MDT Wed Jun 26 2024 .KEY MESSAGES... - Shower and thunderstorm chances return to the area today. - Stronger storms are expected Thursday with the best chances across northern, central, and southern Wyoming. Strong wind gusts and large hail are the primary threats. - Cooler and drier Friday before a warmup begins this weekend. Not much chance of precipitation after Thursday until Sunday night/Monday. && .DISCUSSION... Issued at 404 AM MDT Wed Jun 26 2024 The hot and dry trend finally breaks down today with the arrival of an embedded shortwave trough. This is evident on water vapor satellite currently over western Idaho. This will shunt increased Pacific moisture into the area. At the same time, decent Gulf moisture will return from the east. Accordingly, showers and thunderstorms will begin around sunrise across western Wyoming as the shortwave arrives, moving northeast through the afternoon. With PWAT values of 0.8-1.0 inches, any cell will have the ability to produce brief, heavy rain. The other threat will be the usual strong outflow winds up to around 40 mph this afternoon. Most of this initial activity will move east of the area around 0Z. However, with continued theta-e advection through the afternoon and increasing upper-level forcing, another round of convection is likely to kick off around this time. There is not great consensus on coverage of storms from CAMs though, and for now we have kept PoPs on the lower end for this evening. This may need adjusted up if current trends hold. Otherwise, today will be a little cooler with highs for most remaining below 90 degrees. Stronger forcing arrives Thursday as a deeper and more pronounced wave clips the area. Destabilization through the morning will make for MLCAPE values of 500-1000 J/kg, and by early afternoon convection will fire off across western Wyoming. This activity will quickly move east through the afternoon, likely exiting most of the area by 0Z. Some of these storms will be on the strong side, and the SPC has recently expanded a marginal risk into much of northern, central, and southern portions of the area. The greatest threats will be strong wind and large hail. Cooler air moves in within westerly flow behind the system for Friday. This will make for highs in the 70s and low 80s for most, or a few degrees above normal. There may be a few showers across southern Wyoming and the northern mountains, but the majority of the area will be dry. Guidance favors a building ridge for Saturday and Sunday, returning a warming and drying trend to the area. Sunday, in particular, looks hot with highs returning to the upper 80s west of the Divide and upper 90s east. With a drier airmass and gusty winds, elevated to critical fire weather conditions are likely this weekend. Further out, guidance is hinting at a stronger wave dropping south from Montana Sunday night into Monday. This would bring the next appreciable chance of rain to the area, with the best chances across northern Wyoming. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 955 PM MDT Tue Jun 25 2024 North and northeast winds will continue for the next few hours for sites east of the Continental Divide as a subtle cold front continues to push southwestward. Expect this wind shift to reach KRKS during the early morning hours. Winds decrease throughout the nighttime for east of the Divide terminals. Increasing cloud cover on Wednesday will signal increased atmospheric moisture and a chance (20 to 30%) for showers and thunderstorms during the afternoon and evening hours. Lightning and brief visibility reductions would be the main threat with storms, as severe storms are not expected. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Myers AVIATION...VandenBoogart