728 FXUS65 KBYZ 152231 AFDBYZ Area Forecast Discussion...Updated National Weather Service Billings MT 431 PM MDT Wed May 15 2024 .UPDATE... Updated POPs and removed mention of thunder for much of the area the rest of the day into the evening. Isolated sprinkles or light shower still possible over central and east...less than 20% coverage at best. SW part of our CWA (mainly mountains) does not appear to have ingredients for much convection worthy of measurable precipitation. Thunder may be difficult elsewhere...but a brief rumble could occur...just do not feel worthy of thunderSTORM terminology except far NE zones and around Big Horns. BT && .DISCUSSION... Tonight through Friday night... Trailing end of shortwave will push E through the forecast area tonight. A weak warm front will be over areas E of KBIL later tonight. Current radar showed isolated showers over the area ahead of the wave. Surface CAPE was 500-1000 J/kg E and S of KBIL with not much shear. PWAT's were in the .5-.6 range. Models do not handle these subtle lift situations well, so blanketed area with isolated PoPs early this evening, with higher PoPs in the NE Bighorns, then had low PoPs along and ahead of warm front late this evening and overnight. Expecting a few thunderstorms through 03Z. Inverted-v soundings suggested gusty winds possible with thunderstorms. WNW flow with energy in the flow will be over the area Thursday through Thu. evening. MUCAPE from SREF was 500 J/kg and Bulk Effective Shear will climb to over 30 kt during the day, and PWAT's will be .5-.8 inches. Models showed scattered QPF over the area in the afternoon, shifting E and becoming more widespread in the evening. The morning will be dry, then 20% PoPs move into the NW zones after 21Z. PoPs increase to 40% and shift E of KBIL in the evening. Cannot rule out a few stronger storms based on instability and shear. Will have strong dry adiabatic mixing which will promote breezy and warm conditions. Highest wind gusts will be W of KBIL near 40 mph. Probability of hitting 80 degrees ranges from 40 to 70% at most climate stations. Forecast highs will range from 75-80 degrees over the area. Next strong trough will move SE through the area Friday and Friday night. Two cold fronts will accompany this system. PWAT's will be .5-.8 inches with MUCAPE around 500 J/kg, and Bulk Effective Shear will be 40-50 kt. PoPs increase through the day to 50-80% in the afternoon. Highest PoPs will be over central parts of the area including KBIL. PoPs then decrease from W to E Fri. night. Again, strong thunderstorms are possible in the afternoon and evening. The other concern for Friday will be strong winds. Several areas of strong pressure rises cross the area during the afternoon through late in the evening, which favor strong winds. However, upward motion from the cold front and trough will offset pressure rises. Probability of wind gusts of 48 kt (55 mph) or higher in KLVM will be 42% at 21Z. Nudged wind gusts across the area toward the NBM 90th percentile. Gusts to at least 50 mph are expected W of KBIL, while KBIL will have gusts to around 30 mph. The EFI showed values between .5-.8 in the W, suggesting stronger wind gusts than model climate values. However, SOT was zero, so nothing too extreme was forecast. Will watch this period for possible wind highlights. Arthur Saturday through Tuesday... Unsettled weather associated with general troughing continues through the extended forecast. Models show a potential upper low moving through the state into Saturday morning, with the last of some energy and precip lingering in the far east. With the departing low, cooler temperatures, closer to normals, are in store. Highs in the mid to upper 60s on Saturday and into the low 70s on Sunday. A zonal/NW flow pattern will be in place for much of Saturday before another upper low digs into the northern Rockies on Sunday. Gusty winds in the 20-40mph range are possible Sunday with a cold front passing through with the upper low. The stronger winds are most likely in the western areas where there is a 40-60% chance of wind gusts in the 30s mph. Widespread chances for precipitation will begin Sunday, with a 30-60% chance for showers/thunderstorms through Tuesday. High temperatures Monday and Tuesday will be around normal to slightly above normal with temps in the mid to upper 60s. && .AVIATION... Isolated showers will continue to progress through the area this evening into tonight. The majority of this activity will be weak, with only a low chance for thunder mainly over the Bighorn Mountains late this afternoon. Otherwise, VFR conditions will prevail. For Thursday, isolated showers, with a rumble of thunder or two, are possible, but the overall chance is low. Breezy conditions with wind gusts around 30-35 kts will occur Thursday afternoon along the western foothills from K6S0 to K3HT. Arends && .PRELIMINARY POINT TEMP/POPS... Tdy Thu Fri Sat Sun Mon Tue ------------------------------------------------------- BIL 070 051/079 050/071 043/067 043/067 042/063 045/063 2/W 22/T 28/T 40/U 13/W 24/W 46/W LVM 069 045/076 047/067 037/068 040/064 037/061 040/061 1/B 11/N 16/T 30/U 14/W 24/W 46/T HDN 070 047/079 049/073 041/068 040/069 040/064 043/065 2/W 21/B 48/T 60/U 12/W 23/W 45/W MLS 071 049/077 050/072 043/065 043/069 042/066 044/065 2/W 21/B 36/T 51/U 11/U 22/W 34/W 4BQ 066 048/076 050/078 042/065 043/071 042/064 044/064 2/W 20/B 24/T 61/U 11/U 22/W 45/W BHK 067 045/075 048/074 040/064 039/069 039/065 040/063 2/W 21/B 25/T 52/W 11/U 22/W 24/W SHR 069 044/076 047/077 037/067 041/070 038/060 040/063 2/W 21/B 25/T 60/U 02/T 24/T 55/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings