834 FXUS65 KRIW 220920 CCA AFDRIW Area Forecast Discussion...CORRECTED National Weather Service Riverton WY 320 AM MDT Tue Oct 22 2019 .SHORT TERM...(Today through Thursday) Issued at 254 AM MDT Tue Oct 22 2019 A moist northwest flow in combination with isentropic upglide/warm air advection this morning over the northwest will result in snow developing in that region toward sunrise. This snow is then expected to expand southward into far western Wyoming by late morning. High temperatures on Tuesday should be 5 degrees warmer than what occurred on Monday. Snow levels over the west today should increase to between 6500 and 7500 ft msl. A few inches of snow are expected across the northwestern mountains today. A low-amplitude trough along the central British Columbia Coast early this morning will deamplify today as it pulls southeast into the northern Rockies of Montana/Idaho. This shortwave trough is then expected to pull across the forecast area tonight. On the heels of this trough, a shortwave trough in the Gulf of Alaska now will push southeast across the northern Rockies on Wednesday. The associated cold front is expected to push into northern Wyoming late tonight, and sweep southward to the Divide by mid to late morning. The precipitation is expected to occur generally along and just behind the cold front with the second wave keeping chances of snow into Wednesday evening. The precipitation in the lower elevations looks to begin as rain and snow depending on elevation, but change to snow in couple hours after frontal passage. Overall precipitation amounts still look to be light. The light snow ends Wednesday night with dry and unseasonably cool temperatures on Thursday. .LONG TERM...(Thursday night through Tuesday) Issued at 254 AM MDT Tue Oct 22 2019 Weak ridging and north-northwest flow will continue the dry weather with cold overnight temperatures in the teens to upper 20s. Friday morning. The highs on Friday will be the warmest of the period across most of the state. Saturday will also see warmer highs, with morning lows rebounding as well across the region. The next front will move into northwestern Wyoming early Saturday morning before moving further south across the state through the evening. GFS and ECMWF are in disagreement with the timing of the front, with the GFS being more aggressive in the eastward progression. The position of the jet across central Wyoming combined with the upslope flow would seem to favor Sunday afternoon and evening as the best period for widespread light snow. The pattern does not look very favorable for heavy western mountain or valley snow. Temperatures will again drop will below seasonal normals for Sunday and Monday with most areas only reaching the upper 20s and 30s for highs, and Monday morning lows dropping into the single digits to mid teens. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1118 PM MDT Mon Oct 21 2019 Mainly dry conditions for all but the northwest corner of the state overnight. Expect all terminals to be VFR through 12Z/Tuesday with KJAC the only terminal with the potential for light snow showers between 09Z- 12Z/Tuesday. Light snow will increase across northwest Wyoming through the day Tuesday with IFR/MVFR likely at KJAC after 14Z/Tuesday. All other terminals to remain VFR with the main aviation hazard being gusty westerly surface wind. KRKS will see a slight decrease in wind speed overnight, but overall 20-30kt wind speeds will prevail. Tuesday afternoon will see 15-25kt surface winds blow at KCPR, KRIW, KBPI, and KPNA. Mountain top obscurations will continue west of the Divide through the forecast period, becoming more widespread and lowering during the day Tuesday. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... Issued AT 254 AM MDT Tue Oct 22 2019 Scattered to numerous snow showers over the northwest with a few inches of snow expected in the mountains. Mainly dry elsewhere with warmer temperatures today. Breezy west to northwest winds are expected mainly over southwest Wyoming, the wind corridor from Rock Springs to Casper, and in the mountains. Smoke dispersal will generally be poor to fair over the north, good over central zones, and good to very good over the south. A cold front will push south across the area late tonight and Wednesday. Cooler, wind northerly flow, and a chance of snow with a storm system late tonight through Wednesday night. Snow accumulations are expected to be light at this time with the best chance over northern Wyoming. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...Murrell LONG TERM...Swanson AVIATION...STRAUB FIRE WEATHER...Murrell