Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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957 FXUS65 KRIW 141647 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1047 AM MDT Tue May 14 2024 .KEY MESSAGES... - Showers and thunderstorms will develop across the state today. Stronger thunderstorms will produce locally gusty winds. - Another round of showers will develop on Wednesday, but will be more isolated in nature. - Drier for the latter half of the week, but showers will still be possible across the northern Wyoming mountain ranges each afternoon. && .DISCUSSION... Issued at 205 AM MDT Tue May 14 2024 More active day in store across most of Wyoming today, with showers and thunderstorms. The first in a series of shortwaves is currently racing east across northern WY, and is bringing increasing showers and a few thunderstorms. Radar and satellite trends have shown an increasing trend both in number and intensity of showers across the Bighorn Basin, which correlates well with convective models. Expect this activity to continue east this morning, with shower and thunderstorms generally north of a Pinedale to Riverton to Casper line. A trailing wave hot on the heels of the first wave will sweep into northern WY early this afternoon. The second wave will catch up with the first wave, bringing even more shower and thunderstorm enhancement. CAM models do have most of the activity with this second wave across northern WY this afternoon and evening, but isolated activity will sweep across southern WY right around sunset. Latest soundings show continued inverted-V profile, common for Wyoming, which indicates any storms would produce locally gusty winds. With a jet streak wrapping around the southern end of the trough, best downburst threat would be across southern WY with any isolated thunderstorms. Most activity will fade quickly near sunset with loss of daytime heating, but some shower activity may continue across Natrona County through around 06Z/15. As the trough slowly moves east on Wednesday, broad northwest flow returns in its wake. With modest moisture and trailing instability, some shower activity should develop along the higher elevations of the Absarokas/Winds/Bighorns during peak daytime heating. Northwesterly flow will then take those showers southeastward, keeping a 30-50% possibility for showers reaching into greater Fremont, Natrona, and Johnson Counties. This pattern continues again on Thursday, with showers focusing again on the Bighorns and Absarokas again, but having a bit more trouble detaching from the higher elevations. Lower confidence currently on forecast into the weekend, as one model shows larger trough sweeping in Friday with more showers, while other model has weaker trough passage mainly to the north over the weekend. Cluster analysis of ensembles leans well toward the latter, with continued light shower development on northern mountains, while the trough mainly moves to the north over the weekend. In either scenario, considerable lower level drying is noted, with low humidity Thursday through the weekend. With systems approaching Friday and/or Saturday, gusty southwest winds will ramp up again, especially for southern WY. This would lead to elevated fire weather concerns especially for the weekend. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1028 AM MDT Tue May 14 2024 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals In and out MVFR ceilings at JAC damming across the valley, but VFR at all other TAF sites. Gusty northwest to westerly winds up to 18-25kts to start the period through peak heating. Increasing storm chances on station between 20-01Z at all sites carrying tempo during these times with the hit and miss nature of these isolated thunderstorms. Outflow boundaries exceeding 40kts are possible at RKS but confidence low dependent on the vicinity of these aforementioned storms. After 01Z, storms and winds will diminish into the overnight hours with improving skies by Wednesday morning. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals VFR conditions expected for all sites with breezy northwesterly winds up to 15-25kts. Increasing thunderstorm activity after 21Z as storms west of the Divide push east and expand in coverage. Tempo groups carried for these times through 00-01Z before weakening due to nearing sunset and capping of the environment. Any severe weather activity looks to stay south with only possible gustier outflow winds over 30kts possible. Otherwise, quieter conditions after 01Z with diminished winds into the overnight hours. Lingering light rain at CPR after 06Z with MVFR ceilings likely IAW some of the LAMP/BUFKIT sounding data (70-80%). Improving conditions for other locations with CPR to follow into the next TAF cycle. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Straub AVIATION...Lowe