Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
390 FXUS65 KBYZ 211541 AFDBYZ Area Forecast Discussion...Updated National Weather Service Billings MT 941 AM MDT Tue May 21 2024 .UPDATE... Trough was moving E through the area this morning, producing rain over the far S and some showers from Powder River into Fallon and Carter Counties. Updated PoPs through 18z to better match radar trends. Also adjusted sky cover to increase clouds NE into Fallon County based on obs and satellite imagery. In addition, raised wind gusts for KLVM based on obs. It was still snowing hard on the NE Bighorns web cams...so Warning was in good shape. Snowfall rates should begin decreasing there this afternoon. Arthur && .DISCUSSION... Today through Wednesday night... Upper level low continues to slowly move east across the northern half of Wyoming, with an enhanced baroclinic leaf showing on satellite over central sections of southern Montana/northern Wyoming. Overall this system is looking less impressive than previously advertised with a system ejecting out of the 4 corners pulling energy out of it, and the parent low over southern Canada pushing northwesterly flow further to the south shunting the track a bit further south and funneling dryer air into the area. The result is that precipitation with this system is being confined to the Bighorn mountains and nearby lower elevations today. As a result have cancelled the Winter Storm Warning for the southwest mountains and the northern Bighorn/Pryor mountains. Still expect to see an additional 4 to 8 inches of snow through this afternoon for the area remaining in the Winter Storm Warning. NBM probabilities for over 10 inches of additional snow are around 40 percent for Bighorn mountain locations along the Johnson/Sheridan count line. With winds shifting out of the west- northwest today will see temperatures warming back into the low to mid 60s this afternoon. With the upper trof over the area, isolated to scattered instability showers can be expected over most areas, from this afternoon into the early evening hours. Precipitation with this activity should be under a tenth of an inch for most areas. Locations along I-90 south of Crow Agency have a better than 50% chance for more than a quarter of an inch of precipitation through this evening, including Sheridan Wyoming. Zonal flow to weak ridging will be over the area tonight through Wednesday morning, for dry conditions. Temperatures will drop into the 30s in many locations tonight with the potential for frost development. Take precautions to protect tender vegitation tonight. Next storm system moves quickly from near Seattle Wednesday morning to SE Idaho by Thursday morning. The latest deterministic model runs have come into good agreement with the timing and the track of the system through Wednesday night. Left front jet divergence moves into western zones late in the afternoon and spreads eastward overnight. Winds turn easterly during this same time frame, enhancing upslope lift. The combination of the two will see good chances (40-70%) of precipitation spreading west to east across the area Wednesday night. Snow levels drop from 8500 feet to 6500 feet Wednesday night. NBM snow totals Wednesday night currently range from 2 to 10 inches, heaviest in the Crazy mountains. Issued a Winter Storm Watch for the western mountain zones (Beartooth/Absaroka/Crazy mountains) starting at 6pm Wednesday evening going through Thursday evening. Chambers Thursday through Tuesday... Model agreement continues to support widespread precipitation, including mountain snow, for Thursday into early Friday. The latest NBM probabilities have a 55-85% chance (lowest over the east) of at least 0.25" through Friday and a 35-65% chance (lowest over the east) of over 0.5". For the mountains, this translates to a 60% chance of at least 6 inches of snow. Then, late Friday into early Saturday, shortwave ridging is expected to build in, bringing a brief period of drying and warmer temperatures to Saturday. Another low will move in late Saturday into early Sunday, and potentially linger through early Monday before ridging builds back over the region. Currently, Saturday and Sunday each have a 30-50% chance (lowest over the east) of precip over the plains and a 50-70% chance over the mountains and foothills. Then, as the ridge builds in, conditions are expected to become warmer and dry. High temperatures will be in the 50s to mid 60s through Friday, increasing to mid 60s to low 70s for Saturday. Sunday will drop back into the 60s before a warming trend begins, bringing back highs into the mid 60s to low 70s Monday and into the 70s to near 80 Tuesday. Archer && .AVIATION... Isolated to scattered showers and isolated thunderstorms are possible near all TAF sites through this evening. Areas of heavy rain will periodically reduce conditions to MVFR/IFR. Expect mountain obscuration. Archer && .PRELIMINARY POINT TEMP/POPS... Tdy Wed Thu Fri Sat Sun Mon ------------------------------------------------------- BIL 063 042/067 043/050 036/064 042/071 044/063 043/072 3/T 22/R 79/T 52/R 13/R 55/T 32/R LVM 060 038/060 038/048 033/062 040/065 037/060 038/071 3/T 16/T 9+/T 32/T 15/T 65/R 22/R HDN 063 038/070 044/054 035/065 039/073 044/066 042/073 3/T 21/B 59/T 62/R 12/R 55/T 32/R MLS 063 041/070 045/056 035/061 040/072 045/066 045/071 1/B 21/B 38/T 62/R 11/B 44/T 32/R 4BQ 062 040/070 044/062 036/062 039/073 045/066 044/068 4/T 20/U 27/T 72/R 11/B 34/T 32/R BHK 063 037/069 042/059 034/058 037/071 042/065 042/068 2/R 11/B 17/T 72/R 01/U 34/R 33/R SHR 057 035/066 040/057 033/062 037/071 039/064 040/070 +/T 21/B 48/T 62/R 12/R 45/T 33/R && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...Winter Storm Watch in effect from Wednesday evening through Thursday evening FOR ZONES 67-68. WY...Winter Storm Warning remains in effect until 6 PM MDT this evening FOR ZONE 198. && $$ weather.gov/billings