Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
432 FXUS65 KMSO 151831 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1231 PM MDT Sun Sep 15 2024 .DISCUSSION...A cut off low is deepening off the U.S. West Coast today setting up southwest flow over the northern Rockies. That will keep us cloudy with isolated light showers through tonight. Tomorrow, the low will be down over northern California and will start to move eastward. As it does this, the flow over our region will turn more southerly and set up a good pattern for thunderstorms. Current forecasts just have general thunderstorms with the potential for small hail and gusts around 40 mph. Tuesday and Wednesday the models have the low moving northeast setting up a wrap-around moisture with moderate to heavy rain for central Idaho and western Montana. Among ensemble modeling systems there is quite a lot of variation on the track of the upper level low, and as a result there is also quite a lot of variation in the precipitation amounts. Central Idaho, including Riggins and Orofino, and northwest Montana, including Troy and Libby, are on the western edge of the moisture, so they have some of the most extreme uncertainty in the forecast. On the low end (10th percentile), they have no rain in the forecast, whereas on the high end (90th percentile), they have a 1.25 to 1.5 inches. Further east, the 10th to 90th percentiles range from 0.25 to over 1.5 inches over a 48 hour period which includes places like Missoula, Butte, and Salmon Idaho. We`ll get a break from the rain for the end of the week and into early next weekend. Then ensembles are showing a 10-15 percent chance of a high impact, high elevation snow even late next weekend in northwest Montana. There is a 10-15 percent chance for a foot of snow above 7,000 ft. in Glacier National Park. We`ll continue to watch that potential very closely. && .AVIATION...Southwest flow out of a cut off low system digging along the West Coast is causing mostly cloudy skies and light rain showers this afternoon and evening. These will continue through the night tonight with MVFR conditions at worst expected. Tomorrow as the low starts to progress eastward across northern California, southerly flow sets up over the region and general thunderstorms are expected Monday afternoon. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$