Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
334 FXUS65 KMSO 042020 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 220 PM MDT Sat May 4 2024 .DISCUSSION...A closed low pressure circulation spinning off the coast of the California-Oregon border is quite prominent on satellite imagery this afternoon. This feature, along with an amplifying ridge east of the Continental Divide, will be the main players in the weather over the next couple of days. For this afternoon and well into tonight, higher pressure east of the Divide will power easterly winds gusting to about 20 mph across much of western Montana and Lemhi County, especially along the Divide and higher terrain east of about Highway 93. As the Pacific low makes its way inland across Oregon, it will push Pacific moisture into the Northern Rockies from the southwest. Rain will start over north-central Idaho this afternoon or evening and spread northwest overnight tonight and on Sunday. Cooler temperatures associated with this system will bring snow levels down to about 5000 feet by Monday morning. Motorists should expect snow over Homestake, Lost Trail, and Lolo Passes as well as Gilmore Summit in Idaho. Chances for 2 inches of snow by Monday morning about about 50 to 80%. Unsettled weather will continue on Tuesday, mostly in the form of clouds, rain, and gusty west winds. As this system moves east of the Continental Divide, it will send wraparound moisture into the Glacier Park region of northwest Montana for Wednesday morning. Impacts on Wednesday morning should be limited to high terrain of Glacier Park. One notable exception will be Marias Pass, where there is a 60- 70% chance of about 4 inches of snow on Wednesday morning. The bulk of the low pressure system will move off to the east while a portion of energy drifts back to the Great Basin region during the latter part of the work week. This pattern shift will leave the Northern Rockies in a weak northerly to easterly upper level flow Wednesday through Friday. Temperatures will gradually warm, but still remain below normal. Shower activity is expected to decrease in coverage and intensity each day. Model ensemble solutions are leaning towards a positively tilted ridge over the northwestern U.S. by next weekend. This scenario would mean a warming and drying trend for the weekend. && .AVIATION...An approaching trough from the west and high pressure east of the Continental Divide will result in gusty easterly winds to about 20-25 knots this afternoon and overnight tonight. Expect increasing clouds and decreasing ceilings as the trough approaches. Rain showers will move from southwest to northeast tonight and become widespread on Sunday. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$