FXUS65 KRIW 071655 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1055 AM MDT Mon Apr 7 2025 .KEY MESSAGES... - Today will be warm and breezy. Rain and/or snow chances (30-60%) exist across western and northern Wyoming late tonight through Wednesday. - Elevated fire weather conditions across portions of the area on Tuesday and Wednesday with windy and dry condiditons. - Warm, near record high temperatures forecast Thursday through Saturday. && .DISCUSSION... Issued at 139 AM MDT Mon Apr 7 2025 The axis of the current ridge passes over the state moves through today. This will bring the warmest temperatures of the next few days, with highs in the mid-50s to around 60 degrees west of the Continental Divide (around 50 degrees for western valleys) and mid- 60s to around 70 degrees east of the Divide. A clear sky remains through the morning, with clouds beginning to move into western Wyoming mid-day as the next weather system approaches. Winds begin to increase this morning, notably over the central mountains (Absarokas and Wind River Ranges) and the Wind Corridor (roughly Rock Springs through Casper). Afternoon gusts near 30 mph will be common for these locations, with wind favored areas a bit higher. Winds decrease some tonight, remaining gusty over the mountains. Afternoon minimum relative humidities (RH) drop to around 15 to 20 percent, so areas of elevated fire conditions are possible. A broad trough begins moving into the area late today, flattening the current ridge over the area. The aforementioned wind is one part of this system, the other being precipitation. Rain/snow chances increase across western Wyoming between around 7pm and 9pm MDT. With the warmer temperatures in place, snow will be limited to the mountains, though a little snow may mix with rain at times for the western valleys. Precipitation chances mainly remain over the western mountains and valleys through Tuesday morning, but chances spread across northern Wyoming (namely the Bighorn Mountains) later Tuesday morning and afternoon. Recent high resolution models have precipitation remaining over the higher elevations (and to a lesser extent, the western valleys), with 20 to 30 percent chances for the lower elevations of the Bighorn Basin and Johnson County, with about 15 percent chances around Casper. Precipitation chances linger into Wednesday, though look more limited to northern Wyoming. There may be some isolated thunderstorms Tuesday and Wednesday as well. For wind, Tuesday and Wednesday will be quite gusty. Starting with Tuesday, widespread gusts over 30 mph occur, in a generally west to northwest wind. Some locations will have gusts up to around 50 mph, like the Wind Corridor, or possibly around Cody as winds come off the Absarokas. Winds trend up for Wednesday as the jet stream moves over the state. Widespread gusts of about 30 to 50 mph occur, with favored areas nearing 55 or 60 mph. Will have to watch trends if any high wind highlights are needed. For now, it's too marginal to make a call. Another ridge follows for Thursday, with much lighter winds compared to Wednesday. This will also start bringing temperatures up again. The GFS and ECMWF are in fair agreement of 700mb temperatures Friday, with 6 to 10 degrees Celsius over the area. Friday continues to look like the warmest day, though Saturday will be comparable. Highs Friday are in the 70s for most areas. Long range models are showing a possible cold front moving in for Sunday, which would bring cooler temperatures and possible precipitation chances. With the warmer temperatures, we continue to monitor river levels, though nothing looks concerning at this time, with river forecasts showing snowmelt rises, as is usual for spring. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 1055 AM MDT Mon Apr 7 2025 VFR conditions at all locations throughout the entire period. Winds will increase to 25kts to start 18-20Z at CPR/RKS/COD/BPI and 18kts for JAC/RIW/LND/PNA. Winds will diminish after sunset around 02Z with radiational cooling as clouds lower and increase to 10-15kft ceilings into Tuesday for the remainder of the period. Rain/snow showers likely at JAC (50-70%) from 05-11Z and possible at BPI/PNA (30-50%) from 06-10Z. Lower ceilings and visibility but VFR. Otherwise, winds increase once again Tuesday morning after 16Z at CPR/RKS up to 25kts with others to follow after 18Z and be stronger as well. 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...Wittmann AVIATION...Lowe