Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
637 FXUS65 KMSO 140905 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 305 AM MDT Fri Jun 14 2024 .DISCUSSION...The upper level flow will become southwesterly today as western Montana and north central Idaho is situated between high pressure to the east and a low pressure system moving onto the Pacific northwest coastline. While temperatures will remain warm (similar to Thursday), increased winds aloft and unstable conditions will allow for breezy winds by afternoon and evening. Most areas will remain dry today, other than southwest Montana where a few showers or an isolated thunderstorm is possible. The low pressure system will begin to move inland on Saturday, pushing a cold front through the region. Cooler temperatures are anticipated with widespread showers, especially across northwest Montana. Breezy conditions will continue, and will likely be stronger than Friday. Current model guidance shows a roughly 40 to 60 percent chance that gusts will exceed 40 mph for many valleys in western Montana. This will likely make for challenging conditions for recreationalists on area lakes, as well as for high profile vehicles. Unstable conditions may allow for thunderstorm development across northwest Montana in the afternoon, which could further allow strong wind gusts locally. A significant wet and cold weather system is expected Monday into Tuesday, with a general consensus (around 70-80 percent of model solutions) supporting a closed low feature moving through the region. Current model solutions show a roughly 50 to 60 percent chance that liquid precipitation amounts will be 1.00 inch or more along the Continental Divide into southwest Montana and extending westward into eastern portions of Idaho and Clearwater County. Snow levels are tricky with this particular system as forecast models are notoriously biased too warm with late season closed low systems such as this. Areas that receive the heavier precipitation will likely see snow levels driven to 5000 feet or lower! In fact, similar events to this one, in June 2008 and 2001, produced a small area of valley snow down to 2800 feet. There is insufficient confidence in either low pressure track or intensity currently, but you are encouraged to follow future forecasts as 1 to 2 inches of heavy, wet snow on trees with leaves could easily cause broken branches leading to localized power outages with winter driving conditions over area mountain passes. For terrain above 6000 feet, a trace to 14 inches is possible, while in the Bitterroot, Anaconda, and Pintler Mountains, Bob Marshal Wilderness, and Glacier National Park Region the highest terrain has a 50 to 60% chance of receiving a foot of snow or more. This amount of snow accumulating on trees with foliage could cause branches to go down on back country roads, be prepared. Due to the high impact potential above 6000 feet and moderate confidence of the event actually happening, winter storm watches have been issued along the Continental Divide from the Canadian border through MacDonald Pass on I-90, including Georgetown Lake and the Anaconda and Pintler Mountains. The main snow event will be overnight Monday through Tuesday. && .AVIATION...Winds aloft will increase significantly from the southwest today ahead of an approaching weather system. These winds will be able to mix down into the valleys by this afternoon, with gusts to 25kts common across all of western Montana and north central Idaho. Increased cloud cover is also anticipated today. A few showers or an isolated thunderstorm is also not out of the question, primarily southeast of a line from KHLN to KHRF to KGIC. Showers or thunderstorms will be capable of producing a few localized wind gusts to 35 kts. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Winter Storm Watch from Monday afternoon through Tuesday evening for West Glacier Region. Winter Storm Watch from Monday evening through Tuesday evening for Butte/Blackfoot Region...Potomac/Seeley Lake Region. ID...None. && $$