Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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436 FXUS65 KRIW 212340 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 540 PM MDT Fri Jun 21 2024 .KEY MESSAGES... - Scattered thunderstorms expected this afternoon, ending before sunset, with damaging winds and flash flooding the main concerns. Larger hail cannot be ruled out as well. - Warming trend for the weekend and beyond with mainly dry conditions going forward. && .DISCUSSION... Issued at 1134 AM MDT Fri Jun 21 2024 IR currently depicts southwest flow across the CWA with ample mid to upper level moisture pumping in from the base of the trough. A strong PVA signature can be seen over northwestern Colorado that will be the main trigger for thunderstorm development in the coming hours ahead into the afternoon. Radar shows some dissipating rain showers and a couple of isolated thunderstorms from eastern Sweetwater County extending through Natrona. Stronger storms are expected to continue to develop early this afternoon across Sweetwater County with possible severe hail the main concern being for supercellular in nature. Ample shear over 30kts and steep lapse rates yield to at least quarter to ping pong ball size hail before storms cluster up and push northeastward becoming more of a wind event. The atmosphere has destabilized with clear skies further south extending north and northeastward in the next couple hours. This will allow for forecasted CAPE values to push well over 1000 J/kg even upwards to 1500 in parts of this area and further northeastward. CAMs are showing storms cluster together by 3-4PM through central portions of the CWA becoming more of a damaging wind threat with gusts over 60 mph and flash flooding concern going forward into the evening hours. DCAPE values show similar conditions with PWAT values up to an inch in some areas east of the Bighorns to the I-25 corridor. If this main upper level trough progs to stay more progressive as models suggest, flooding may not be a high concern going forward. Severe watches are currently issued with more to come this afternoon and evening before storms weaken and push east by 7-8PM towards sunset losing the ingredients with radiational cooling. Going forward, ridging builds back in from the subtropical high over west Texas that will bring a warming trend and mainly dry conditions to the CWA for the weekend and much of the next week. Temperatures well into the mid to upper 90s for points east of the Divide to include possible 100 degrees through the Bighorn Basin. An upper level low looks to come out of the Gulf of Alaska down to the Pacific Northwest, but the main finger of the PFJ looks to stay north only clipping any minor impacts to northern parts of the CWA by week`s end in terms of light precipitation and general thunderstorm activity for higher elevations. All in all, today is the last chance for widespread rainfall going forward with dry conditions and elevated fire weather becoming a concern for much of next week into the long term outlook. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 540 PM MDT Fri Jun 21 2024 Showers and isolated thunderstorms have become more focused over areas east of the Divide late this afternoon. An additional line of thunderstorms will exit eastern portions of Sweetwater County in the next hour or so, while isolated thunderstorms remain possible over far western portions of the forecast area. The window for severe thunderstorms is quickly closing over Johnson and Natrona counties, with an area of stratiform precipitation pushing eastward into those areas currently. This trend will continue this evening, with most of the precipitation ending between 03Z and 06Z. Winds will decrease for the overnight hours and clearing skies after 06Z. Dry westerly flow then moves in Saturday, with isolated storms south of KRKS Sat afternoon, and some mid-level clouds across the MT/WY border. Hot and dry conditions then move in for the rest of the weekend. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Lowe AVIATION...McDonald/LaVoie