Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
600 FXUS65 KBYZ 062111 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 311 PM MDT Mon May 6 2024 .DISCUSSION... Tonight through Tuesday night... Dynamic upper low currently over northeastern WY is affecting our weather in several ways, with a severe thunderstorm threat over Carter and Fallon Counties as low-level east/southeasterly winds bring relatively warm, moist air and associated instability to those areas, steady rain over central areas, snow in the Bighorn Mountains, and strong gusty winds over western and central areas. Ensemble means generally show 500 mb low meander over the western Dakotas into Tuesday night, with more weather impacts for our area. They also show 700 mb winds strengthening over our area late this afternoon-evening then staying strong through Tuesday night. At the surface, low pressure probably in the lower 980s mb will also meander in the western Dakotas. As we go through the rest of this afternoon, the surface boundary in Carter/Fallon Counties should move northeastward and the area of appreciable instability will depart the area. Thus, the severe thunderstorm threat should diminish late this afternoon or early evening. The Severe Thunderstorm Watch for Carter and Fallon Counties is in effect until 7 PM MDT tonight. Main hazards from the thunderstorms will be strong, damaging wind gusts and large hail. The surface pressure gradient between the surface low to our east and higher surface pressure to our west plus strong 700 mb winds over our area should support more strong, gusty winds over much of the area tonight into Tuesday evening. Look for wind gusts to 50-60 mph through Tuesday night, so have extended the High Wind Warning and expanded it in area to include much of the lower elevations except for Fallon County. If you will be traveling with a high profile vehicle during this time please use caution. The low pressure system should also bring more precipitation to the region. A band of rain forced by frontogenesis is gradually sliding eastward, east of Billings, into southeast MT. Look for much of the additional rainfall tonight into Tuesday morning to occur in southeast MT, where large-scale ascent and frontogenesis work constructively to produce precipitation. NBM shows a 30-65% chance of at least 0.75 inches additional rain tonight from roughly Rosebud/Treasure Counties eastward to the Dakota border. Greatest probability is near Miles City. Then for Tuesday afternoon a disturbance rotating around the upper low should bring another round of rain into Tuesday night to much of the area including Billings. The combination of rain and wind will make for unfavorable conditions for travelers and anyone outdoors. Snow in the Bighorn Mountains will continue into this evening before diminishing. Additional snow accumulation there will be up to 7 inches or so. Use caution if you will be heading to the high country. Snow should return to the Bighorn Mountains Tuesday afternoon into Tuesday night. Low temperatures will generally be in the 30s and 40s tonight then 30s Tuesday night. High temperatures on Tuesday will be in the 40s and 50s. RMS Wednesday through Monday... Cool and unsettled weather to start the extended period, then dry weather with a warming trend expected. On Wednesday, models were not in good agreement with the position of the upper low that is affecting the area during the short-term. Upper low was progged to be E or SE of the forecast area depending on the model. Either way, cyclonic flow will be over the region and a back-door cold front moves SW through the eastern part of the area. PWAT`s are forecast to be around normal for this time of year with not any notable instability. Highs will only be in the 40s and 50s. With plenty of energy in the flow aloft, PoPs are high, near 100% through the day. NBM probabilities of a half /0.50/ inch or more of rainfall were 58% for KBIL and 39% for KSHR on Wednesday. And the EFI had a high value of .8 for snow over areas NW and S of KBIL (this includes Tue. night). So have a mix of rain and snow W and S of KBIL mainly in the morning. Not expecting any low elevation snow accumulation, but the mountains will have decent accumulation with close to a foot in the highest elevations of the Beartooths/Absarokas. In addition, winds will still be an issue based on the ECMWF ensemble, and the EFI showing .8-.9 over the SW half of the forecast area. Gusts into the 50s are not out of the question for this area. For Thursday, upper ridge builds in from the W and results in a high over low pressure situation. PoPs remain moderately high, from 40-60% through Thursday. Low- elevation rain with mountain snow will continue, with the mountains picking up a few more inches of snow. Highs will be near normal. A high over low situation will continue through Saturday with model differences. Other than some low PoPs over the NE Bighorns, the area will be dry with highs climbing into the 70s. NW flow will be over the area for Sunday and ridging or zonal flow will be over the region on Monday. Next best precipitation chance is Mon. afternoon with 20-40% chances of showers and thunderstorms. Arthur && .AVIATION... Strong wind gusts will continue tonight through Tuesday with NW winds gusting from 45 to 55 kt, and lighter winds in the KBHK area. From KBIL-KSHR W, expect MVFR to VFR conditions. E of this line, there will be IFR/LIFR conditions due to rain and thunderstorms. Severe thunderstorms, with wind gusts to 65 kt and large hail, are possible over Fallon and Carter Counties through this evening. Conditions will be from MVFR to LIFR over the entire area Tue. afternoon. Expect localized to areas of mountain obscuration through Tuesday. Arthur && .PRELIMINARY POINT TEMP/POPS... Tue Wed Thu Fri Sat Sun Mon ----------------------------------------------------------- BIL 043/051 039/050 043/060 042/069 045/075 047/077 049/076 46/W 9+/W 97/T 11/U 01/U 11/U 13/T LVM 037/049 036/046 038/057 037/065 040/071 043/073 045/074 15/W 9+/W 84/W 10/U 01/U 12/W 13/W HDN 041/050 037/053 042/062 040/069 041/075 044/078 046/077 +8/W ++/W 97/T 21/B 01/U 11/U 12/W MLS 039/045 039/055 042/063 043/067 043/074 045/076 047/076 99/W 99/W 64/W 11/U 01/U 11/U 12/W 4BQ 037/045 037/051 041/060 043/066 041/072 045/076 047/075 +8/W 99/W 85/W 11/B 01/U 11/U 12/T BHK 036/045 034/054 038/063 040/065 040/070 042/073 044/074 89/T 88/W 43/W 11/U 01/U 01/U 11/U SHR 039/053 034/046 038/057 037/064 037/070 041/073 043/073 74/W 9+/W 97/T 21/B 01/U 12/T 13/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...High Wind Warning in effect until midnight MDT Tuesday night FOR ZONES 29>32-57-173. Severe Thunderstorm Watch 188 in effect until 7 PM MDT this evening FOR ZONES 33-37. High Wind Warning now in effect until midnight MDT tonight FOR ZONES 34-42-138-170-235. High Wind Warning in effect until 6 PM MDT Tuesday FOR ZONES 36-37-58. High Wind Warning remains in effect until 6 AM MDT Wednesday FOR ZONES 63-65-66-141-172-228. WY...High Wind Warning now in effect until midnight MDT tonight FOR ZONE 199. Winter Weather Advisory remains in effect until midnight MDT tonight FOR ZONE 198. && $$ weather.gov/billings