Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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580 FXUS65 KRIW 232134 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 334 PM MDT Thu May 23 2024 .KEY MESSAGES... - Light to moderate mountain snow and lower elevation rain/snow showers will continue through the afternoon. - Gusty winds continue for much of the area through the afternoon. - Precipitation and wind will end after sunset. Most areas will see a frost or freeze tonight. - Warmer and drier Friday before unsettled conditions return for the weekend. && .DISCUSSION... Issued at 324 PM MDT Thu May 23 2024 Cooler and wetter conditions are ongoing today as a low pressure system rotates across northern Wyoming. The precipitation focus last evening was across the western mountains, with 6 to 10 inches of snow noted on area webcams. That focus has now shifted to northern areas as the low moves farther east. Precipitation will continue through the afternoon, though the heaviest amounts will generally remain along and north of the Wyoming/Montana border. Snow will be heaviest across the upslope favored, north facing slopes, including in the northern Absarokas and Bighorns. The main impact from snow will be slick roads in spots, especially over Teton, Togwotee, and Granite passes. A Winter Weather Advisory remains in effect through most of the afternoon for the Tetons, Gros Ventres, and Bighorns. Otherwise, rain showers will move farther south toward the Continental Divide through the afternoon, though again most of this will fall in the Bighorn and Powder River basins. The other aspect with the system today is wind, with gusts of 35 to 45 mph noted across much of the area this afternoon. This will continue for the next several hours, with a few isolated gusts over 50 mph likely (70%) within the Wind Corridor from Rock Springs through Casper. Both precipitation and wind will quickly decrease from west to east after sunset as the system moves away. With clearing skies overnight it will make for a chilly morning. Lows around or just under the freezing mark are expected for much of the Bighorn Basin; given that they are past the average last freeze date, we will be upgrading the Freeze Watch to a Warning. Friday will be warmer and drier as a weak transitory ridge takes over, though still about five degrees below normal for this time of year. Returning southwest flow near the surface will make for a breezy afternoon for most locations while mixing down drier air moving in aloft. This will return slightly elevated fire weather conditions to much of central and southern areas where humidity will drop below 20 percent. Unsettled conditions will then return Friday evening as the next shortwave arrives. This will bring light showers across southern areas through Saturday morning, followed quickly by the arrival of a weak trough axis connected to a low positioned well to our northwest. This feature appears likely to bring another round of showers from west to east across the area through Saturday. Amounts do not look very impressive right now, and will likely fall as scattered light rain showers given the warmer temperatures of this system. Guidance then shows the low clipping northern Wyoming on Sunday, with showers focused more east of the Divide. Memorial Day will be warmer and dry as stronger ridging returns to the area. Further out, ensemble guidance generally favors ridging persisting through midweek before weakening by the weekend. This would keep drier conditions and temperatures around or above normal through much of next week. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1145 AM MDT Thu May 23 2024 The last wave of the upper low pressure system will push through today. Showers will mostly be confined to the north (KJAC, KCOD, KWRL terminals), though there is a chance (20%) that KPNA, KRIW, and KCPR terminals could see some brief rain showers this afternoon and evening with best chances (50%) at KRIW. MVFR conditions are expected with the showers at the aforementioned terminals. KJAC will see IFR conditions with snow showers through the first few hours of the period, with conditions improving to MVFR and prevailing as such through the rest of the afternoon. All terminals should see prevailing VFR conditions and cloud cover beginning to scatter out by 06Z tonight. Winds will be gusty through much of the afternoon at most terminals this afternoon. A northerly push will continue to move through the Bighorn Basin and impact KRIW and eventually KCPR terminals around 00Z-02Z. This northerly push will be associated with a cold front and accompanying rain showers. Winds will decrease overnight (by 06Z) and increases in winds Friday morning will be limited to the favored locations (KPNA and KCPR). 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... Freeze Watch from midnight MDT tonight through Friday morning for WYZ003>006. Winter Weather Advisory until 6 PM MDT this evening for WYZ008- 009. Winter Weather Advisory until 4 PM MDT this afternoon for WYZ012. && $$ DISCUSSION...Myers AVIATION...Hensley