Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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118 FXUS65 KRIW 150302 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 902 PM MDT Fri Jun 14 2024 .KEY MESSAGES... - Isolated thunderstorms will produce 45 to 55 mph outflow wind gusts this evening through sunset, after which time storms will dissipate. - Temperatures continue to run 10 to 15 degrees above seasonal normals through the day Saturday. - Breezy winds are expected on Saturday combined with temperatures well above normal, leading to elevated fire weather conditions. Shower and thunderstorm activity will be minimal. - Temperatures begin cooling on Sunday, and below average temperatures are expected by Tuesday as the next weather system moves through. && .DISCUSSION... Issued at 255 PM MDT Fri Jun 14 2024 A strong ridge of high pressure continues to dictate the weather pattern for Wyoming over the next 36 hours, with temperatures remaining 10 to 15 degrees above normal. As a trough slowly pushes onto the West Coast this afternoon, a shortwave focused over Montana has provided lift for some thunderstorms, primarily across southern Montana, just north of the Wyoming border. Over western and central Wyoming, dynamics are not as favorable, but scattered diurnal-heating-based "garden variety" thunderstorms will still produce gusty outflow winds on the order of 45 to 55 mph due to the large temperature-dew point spreads (indicative of efficient evaporation and cooling of downdraft air parcels). After sunset storms will quickly dissipate. Overnight RH recovery will be relatively poor and thermal belts are likely for midslopes. Any fire activity is likely to be more vigorous than on a typical overnight. On Saturday, the trough over the Pacific Northwest will continue inching eastward, tightening the pressure gradient. Most areas across Wyoming will see strong sustained westerly winds develop by noon, with gusts in the 35 to 50 mph range. The higher gusts will be focused over the wind corridor from Sweetwater to Natrona County. Isolated thunderstorms are again possible on Saturday afternoon, but these will be focused over the Powder River Basin and quickly move into eastern Wyoming by mid- afternoon. Gusty outflow winds are again the main threat with any of this convective activity. Sunday and into early next week the trough to the west will begin to influence sensible weather more. Temperatures will cool to seasonal normals, and areas along the northern third of the state will likely (40 to 70% chance) see light measurable rain Monday into Tuesday. Tuesday will even feature temperatures below seasonal normals for the first time in over a week. Temperatures moderate for the second half of the week, with above average highs again in the forecast by Friday. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 902 PM MDT Fri Jun 14 2024 Some lingering rain showers and thunderstorms are near KRKS/KPNA thanks to a rogue outflow boundary that is moving northwest. This outflow boundary looks like it has finally stalled just southeast of KPNA, so no new convective development is expected with this tonight as the recent convective activity dissipates. Conditions will remain VFR through the TAF period. Model guidance is now depicting convective development in Natrona and Johnson County Saturday afternoon, which means a chance for storms in the vicinity of KCPR for a couple of hours. Strong surface winds should prevent any rogue outflow boundaries associated with this convection from pushing west and initiating more convection in the area, so thinking is just a short window for thunderstorms at KCPR Saturday afternoon. Wind will increase Saturday morning and become strong across the area through the afternoon. Wind gusts will average 25-35 knots (as high as 45 knots) Saturday afternoon. 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...VandenBoogart AVIATION...Rowe