Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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867 FXUS65 KRIW 271701 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1101 AM MDT Sat Apr 27 2024 .KEY MESSAGES... - Rain showers and mountain snow will continue today. - Some showers linger tomorrow, but coverage looks to be less. - The forecast has trended more unsettled next week with a couple of rounds of showers and strong wind, but confidence in details remains rather low. && .DISCUSSION... Issued at 242 AM MDT Sat Apr 27 2024 Precipitation is ongoing across approximately the western half of the area, with emphasis on the easterly upslope areas against the Wind River Range, Absarokas and the Salt and Wyoming Range. One place that has overperformed has been Dubois, where a perfect low level upslope flow (around 120 to 130 degrees) and good precipitation rates have cooled temperatures to around freezing to bring a couple of inches of snow, including some on the roads. Most other areas have just wet roads, with the exception of South Pass where the Winter Storm Warning is in effect. Snow levels look to remain around 7500 feet or so through the day. Precipitation will continue today, although intensity East of the Divide should begin to decrease this afternoon as low pressure over Colorado begins to move away, starting to shut off the moisture. It still looks like some good rates in the morning though, so we will continue the highlights as is for now. A trailing trough axis will move into western Wyoming this afternoon and bring a round of showers into the evening. It is possible a few locations may receive advisory level amounts, especially in the Tetons and Salt and Wyoming Ranges. We will not issue any highlights though. The heaviest precipitation will fall in the afternoon, and given recent warm weather and the almost May sun angle, snow should have trouble sticking to roads. In addition, the heaviest snow would fall above pass level where impacts would be minimal. We will issue some Special Weather Statements to cover for this though. This trough axis will then slowly move across the state on Sunday, and bring some additional showers and isolated thunderstorms. Coverage will be less though, especially East of the Divide where the chance will be generally less than 1 out of 2. Past Sunday, uncertainty in the forecast increases significantly. The main driver of the weather will be an upper level low moving in from the northern Pacific, into the Pacific northwest and across the northern Rockies through at least midweek. Deterministic and ensemble guidance has trended further south with some shortwaves rotating around the low, which would increase shower coverage across the area through midweek. There is some agreement on the main waves moving through on Monday and Wednesday, with a break on Tuesday. There are still differences on exact timing and placement of the heaviest precipitation. Guidance also differs on when the low kicks east of the area, differing by as much as 36 hours. There has been poor consistency though, with the deterministic models flip flopping over the past couple of days. So, although we around a 1 in 2 chance in confidence on some unsettled weather continuing, confidence is very low in the details. Strong wind is also possible Monday through at least Wednesday with the jet over the area, but confidence in meeting high wind criteria is mixed, basically a 1 in 2 chance or a coin flip. Ridging should bring some drying toward the end of the next work week. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1047 AM MDT Sat Apr 27 2024 Mainly VFR conditions for the entirety of the period with LND lifting right above to start the period. JAC is likely to see MVFR ceilings and visibility with light rain on station between 01-05Z. Otherwise, lifting to VFR after and to the end of the period. Elevated winds at BPI, PNA, RKS, and CPR gusting up to 18-25kts through about 00-01Z before diminishing due to radiational cooling and improving skies. Mid level ceilings remain overnight scattering out by the end of the period around 16-17Z and winds less than 10-12kts. Winds will increase at BPI, COD, PNA, and RKS with daytime heating and mixing to the surface after 16-17Z lasting into the next period. No other weather elements are expected with aviation weather much improved from the past day or two. 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... Winter Weather Advisory until 3 PM MDT this afternoon for WYZ002. Winter Storm Warning until 9 PM MDT this evening for WYZ015. && $$ DISCUSSION...Hattings AVIATION...Lowe