Expires:No;;222336 FXUS65 KRIW 252215 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 315 PM MST Thu Dec 25 2025 .KEY MESSAGES... - Though remaining gusty, winds decrease this afternoon. Rain and snow also decreases this afternoon. - Record-breaking temperatures today, with the warm temperatures continuing for tomorrow. - A weather system Friday brings western snow and widespread gusty winds over 30 mph, with many areas over 40 mph. This system also brings a cold front Saturday, which brings much cooler (but seasonable) temperatures for the weekend. && .UPDATE... Issued at 1232 PM MST Thu Dec 25 2025 The isolated light rain and snow showers decrease through the afternoon, along with the strongest winds from last night and this morning. Gusty winds are still expected over the mountains and the usual locations, like from South Pass to Casper. Widespread winds increase early Friday morning. Evidence is not quite high enough for any wind highlights Friday, with 700mb winds only peaking about 45 knots. That said, widespread gusts 40 to 50 mph are still forecasted across portions of the area, and localized wind prone locations, like Outer Drive in Casper, could see gusts more in the 50 to 60 mph range. For snow with Friday's system, guidance would suggest at least advisory amounts over the western mountains. With relatively colder temperatures in place Friday, (snow levels 6000 to 6500 feet) would actually have better confidence in snow amounts compared to the recent warmer systems where snow amounts generally underperformed compared to what was forecasted. Winter Weather Advisories have been issued to cover this snow. Main weather impact concerns would be for any travel over mountain passes, (Teton, Togwotee, South, etc.) where snow and wind could bring some winter travel conditions. && .DISCUSSION... Issued at 152 AM MST Thu Dec 25 2025 The weather has been exceptionally abnormal across western and especially central Wyoming for much of this month. This year, it seems like the snow miser has been on a two month long leave of absence with only cameo appearances and is still nowhere to be found. At the office as I write this, our office is sitting at 53 degrees, which is the average HIGH temperature for Raleigh, North Carolina, where I went to college back in the dark ages called the 90s. And it looks like we will have another day of record warm temperatures, mainly east of the Continental Divide. One of things bringing this though is strong to high wind, courtesy of an approaching trough and an 120 knot jet over the area. We have High Wind Warnings out roughly from South Pass through Casper through 11 am this morning. Most guidance shows 700 millibar wind remaining 50 knots or more through this period before decreasing, and bringing lighter wind as a result. The area still looks good with most areas having at least a 3 out of 5 chance of wind gusts past 55 mph. There could be a few high gusts around Lander as well, but these would be isolated. We will issue a Special Weather Statement to cover for this. And we have a snowy part of the system as well. Snow has been falling largely above 8000 feet today, bringing slick conditions to the mountain passes, mainly Teton and Togwotee passes. The current Advisory looks to be in good shape right now, although a bulk of the snow should fall before noon as the best forcing moves east of the area by that time. We will continue as is for now. Snow levels may fall to around 7000 feet this afternoon, so there could be some light accumulation in the valleys, but nothing to write home about. There should be a lull in the snow and wind later this afternoon and through tonight. Then, another Pacific trough will approach the area. There is a bit more uncertainty with this one, as the models have different placement of the heaviest QPF. Ensemble guidance gives a greater than 4 out of 5 chance of over 6 inches of snow in the western mountains through Saturday. Chances of 12 inches are more limited though, generally less than 1 out of 2. And areas that have the greatest chance are the Wind River Range and southwestern Yellowstone, areas where impacts are fairly limited. I could see some more highlights here, but will hold off for now with the current Advisories so as not to confuse people. One difference here is that colder air will be in place, with 700 millibar temperatures falling to minus 9 Celsius by Friday evening across the western valleys, making most of the precipitation in the form of snow. Chances of over 3 inches in the valleys remain small, generally 1 out of 3 or less though. Although there will not be a white Christmas, it could be a white Boxing Day, at least late in the day. Some snow could even make it in southern Wyoming in the afternoon or evening, but accumulations here should remain on the light side. As for east of the Divide, there will be one more mild day. However, the peak of the heat will be today with temperatures about 10 degrees cooler on Friday than Christmas day as 700 millibar temperatures fall about 5 degrees Celsius. It will still be well above normal though. There could be another period of high wind as well, as the pressure gradient tightens ahead of the trough and southwest flow increases with 700 millibar wind again reaching 50 to 55 knots. Ensembles are giving a greater than 1 out of 2 chance of wind gusts past 55 mph from South Pass through Casper and also in the Lee of the Absarokas. We will hold off on any highlights for this, given the current ones in effect. If conditions look likely, we can issue on the day shift today or early Friday morning. As for precipitation, chances look small again with the downsloping flow. There will be one more system for Saturday, and that will really put an end to the mild weather, at least temporarily. This will be in the form of a Canadian cold front that will bring a colder airmass from, you guessed it, Canada. As for precipitation, given the continental origin, moisture is limited and with the front's fast movement, amounts would be light. Many areas east of the Divide could see some snowflakes for the first time in a while though on Saturday into Saturday night. Temperatures then return to levels more normal for late December on Sunday. The numbers we have in the forecast may be the coldest they could get though. If there is little or no snow on the ground, albedo would be limited. It will feel rather cold though, given the recent balmy weather. The cold weather won't last long though, as ridging builds back over the area and flow turns westerly again for much of next week. This will bring a return to above normal temperatures, although not as warm as this past week. It will also likely be rather windy at times given the fast zonal flow. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 315 PM MST Thu Dec 25 2025 West of the Continental Divide...KJAC/KRKS/KPNA/KBPI Terminals Breaks in the cloud cover combined with favorable instability has allowed for scattered convective showers Thursday afternoon. Even a few rumbles of thunder have been observed. The convection tracks northeast until 01Z-03Z/Friday when instability wanes and showers dissipate. Brief MVFR is possible with these showers, but these will be quick-hitting in nature. The next wave of Pacific moisture reaches western Wyoming between 05Z-08Z/Friday, with KJAC seeing the earliest precipitation. Initial light rain around 06Z/Friday changes to snow at KJAC late tonight before intensity increases and IFR conditions develop around 12Z-14Z/Friday. MVFR light snow holds off until closer to 18Z/Friday at KPNA/KBPI. Gusty surface southwest wind 15-30kts returns to KRKS late Friday morning and continues through the remainder of the period. KJAC sees an increase in south- southwest wind 10-18kts in association with the Friday morning snowfall. Mountain tops occasionally obscured, with mountains obscured after 06Z/Friday. East of the Continental Divide...KCPR/KCOD/KRIW/KLND/KWRL Terminals Passage of a midday shortwave and convective outflows have played havoc with surface wind speeds and directions across central Wyoming Thursday afternoon, impacting KCPR, KRIW, and KLND. In general, KCPR and KCOD to keep a gusty 12-25kt southwesterly wind overnight, while downsloping wind of similar intensity returns to KLND early in the period. Speeds increase again at KCPR, KCOD, and KLND late Friday morning, while KRIW and KWRL hold off until 18Z-19Z/Friday before westerly wind picks-up. Lingering Thursday late day convective showers fade between 01Z-03Z/Friday. A few showers drift east off the Absaroka and Wind River Mountains Friday afternoon, but impacts would be limited in duration at KCOD and KLND so have left out PROB30 at this range. Mountain tops occasionally obscured. Please see the Aviation Weather Center and/or CWSU ZLC and ZDV for the latest information on icing and turbulence forecasts. && .CLIMATE... Issued at 152 AM MST Thu Dec 25 2025 Another day of record high temperatures are likely today across much of the area. There were eight record high temperatures at our nine official climate sites yesterday, with only Big Piney not having a record high. Two locations, the Riverton Airport and Greybull had their all-time warmest December temperature on the afternoon of the 24th. This brings the total of record high temperatures this month so far at our nine official climate sites to 59. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 5 AM to 11 PM MST Friday for WYZ001-002-012-014-024. && $$ UPDATE...Wittmann DISCUSSION...Hattings AVIATION...CNJ CLIMATE...