Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
293 FXUS65 KMSO 241906 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 106 PM MDT Mon Jun 24 2024 .DISCUSSION...Westerly flow aloft with the upper level jet positioned just north of the border and some low level instability will keep the forecast for this afternoon dry and windy for much of the Northern Rockies. Westerly flow gives way to a ridge of high pressure on Tuesday. While dry (low relative humidity) conditions continue, winds will relax under the ridge. Daytime high temperatures on Tuesday through Wednesday will rebound back up from today, reaching the upper 80s to low 90s in the valleys of western Montana, and the mid to upper 90s in western Idaho and Clearwater Counties. As the ridge moves east on Wednesday, a trough of low pressure will approach the Pacific Northwest. Flow aloft will transition to the southwest, bringing Pacific moisture with it. There will be enough instability, wind shear, and moisture available on Wednesday afternoon to fuel thunderstorms across Lemhi County and southwest Montana (20 to 30 percent chance), as well as Idaho County and northwest Montana (about 15 percent chance). Model forecast soundings indicate potential for strong winds (30 to 40 mph gusts) associated with any thunderstorms that are able to form. A cold front associated with this system will pass on Wednesday afternoon or evening, resulting in temperatures dropping to slightly below normal for the balance of the work week. The low will arrive in the Northern Rockies by Thursday afternoon. Expect widespread rain and enhanced westerly winds. The northerly track of the low and the southerly position of the upper level jet will favor northwest Montana and Clearwater County for precipitation and southwest Montana and Lemhi County for wind. Salmon will have about a 60% chance of exceeding 30 mph gusts, and Butte will have about a 30% chance. The wettest area will be along the Canadian border and the Continental Divide north of about Highway 200, where there will be about a 40 to 50 percent chance of exceeding 0.25 inches by Friday morning. Friday will be a transition, as high pressure begins to build back for Saturday morning. Model consensus is favoring high pressure for Saturday. Agreement breaks down on Sunday, with about 40% of ensemble solutions showing more unsettled weather. && .AVIATION...A ridge building over the region today and tomorrow will keep aviation impacts to a minimum with VFR conditions today and tomorrow. Expect gusty west winds of 20 to 25 knots at KSMN and KBTM through this evening. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$