Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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557 FXUS65 KRIW 040335 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 935 PM MDT Wed Jul 3 2024 .KEY MESSAGES... - An unsettled weather pattern continues through this week as a trough remains over Wyoming. - Scattered rain showers and thunderstorms have developed across northern Wyoming this afternoon. Small hail and gusty wind is possible with these storms. Elevated fire weather conditions are occurring across southern Wyoming and will through this afternoon. - The weather pattern favors breezy to windy conditions for the next 7 days and mostly dry conditions beyond Thursday. A heat wave is looking more likely to begin next week as a strong ridge moves into the region. && .DISCUSSION... Issued at 155 PM MDT Wed Jul 3 2024 Troughing will be the general weather pattern through this weekend, with several waves within the trough sliding through Wyoming. Independence Day (The 4th of July) looks pleasant temperature-wise as cooler air moves into the area behind the weather system moving through today. The current high temperature forecast is for upper 60s to middle 70s across the area. The wave today has resulted in scattered rain showers and thunderstorms across the northern half of the area. Who gets a good wetting rain with these showers and storms will depend on where they develop, but about from YNP eastward through the Bighorn Basin and into Johnson County is likely to have measurable precipitation from Wednesday through Thursday. Currently, the SPC has a Marginal risk of severe weather in the Bighorn Basin eastward into Johnson County for large hail and damaging wind, but this threat looks to be very low based on how things have developed this afternoon. Still, it is best to stay alert, especially in northern Johnson County where the best chance of severe weather exists. Once the wave passes by on Thursday the cooler air aloft will allow for isolated convection to develop. The best chance will be along/near the Absaroka Mountains/Bighorn Mountains where afternoon upslope will contribute to lift. Localized heavy rain will be a threat on Thursday, especially in or near the Bighorns as northwest flow sets up and may lead to the formation of some training convection in the Bighorns. PWAT`s don`t look excessive, so not expecting widespread flash flooding. Model guidance has diverged on the flow pattern for Friday. The GFS shows northwest flow greatly weakening, whereas the ECMWF now has a wave/weak upper-low clipping the area. Am leaning toward the GFS solution which would be more of a consistency forecast since models have been showing weaker flow with that wave further north and east. As such, mostly clear skies on Friday will allow for temperatures to get back to about normal. Model guidance has another wave coming down in northwest flow this weekend, which will bring low chances for isolated convection to mainly northeastern portions of the area. This looks like the last gasp for the trough that has been sitting over the region as a large amplified ridge pushes into the western US early next week. This ridge will bring hotter temperatures back to Wyoming and heat will become the most impactful weather well into next week based on what long-range model guidance is depicting. && .AVIATION /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 930 PM MDT Wed Jul 3 2024 Any remaining showers across the area will end by 08Z. Winds will also continue to subside through the rest of the night. West- northwest winds, with gusts around 25 kt, will return to KBPI/KPNA and KRKS by 18Z, while winds will keep a northerly component across areas east of the Divide. Showers and thunderstorms will be possible again across northern portions Thursday afternoon, but coverage may not be as widespread as today. Confidence remains too low to include in any terminal forecast at this time. Winds west of the Divide will begin to subside after 01Z, with light winds across the forecast area by the end of the TAF period. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .FIRE WEATHER... Issued at 155 PM MDT Wed Jul 3 2024 Elevated fire weather conditions will continue across southern fire zones this week. The worst days will be today and Saturday as wind increases ahead of weather systems and RH will drop into the teens each afternoon. For northern zones, wetting rain is possible (40-50%) this afternoon/evening and even into Thursday for The Absaroka Mountains/Bighorn Mountains. Lightning will be frequent with thunderstorms on Wednesday and Thursday, but the storms should have a good amount of moisture with them, so the chance of dry lightning is low (<10%). Smoke dispersal looks to be at least good in the afternoon for the next few days at least. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Rowe AVIATION...LaVoie FIRE WEATHER...Rowe