Marine Weather and Tide Forecast for Bigfork, MT

FXUS65 KMSO 150930 AFDMSO

Area Forecast Discussion National Weather Service Missoula MT 230 AM MST Wed Jan 15 2025

DISCUSSION

KEY MESSAGES:

- Arctic front to bring the coldest temperatures of the winter this upcoming weekend into Monday.

- Elevated risk for dangerous wind chills (-30F or colder) along the divide Sunday night into Monday morning.

Valley inversions have developed over the past 24 hours as a broad ridge of high pressure settles over the region. These inversions will strengthen this afternoon as the ridge axis moves overhead, leading to modest warming at higher elevations. Valley high temperatures are expected to remain in the upper 20s to low 30s across the US-93 corridor, from Eureka south through the Flathead, Missoula, Bitterroot, and Salmon, Idaho Valley areas.

Model guidance shows strong agreement on a trough of low pressure digging southeastward across the Northern Rockies from British Columbia Thursday night into Friday. Snow showers are expected to develop along a cold front dropping south from Canada, with valley snow accumulations focused along the I-90 and Highway 200 corridors from Missoula eastward. Most valley areas will see light accumulations, ranging from a trace to up to 2 inches, as this system has limited moisture.

A secondary push of modified arctic air will move along the divide Friday morning, with a 50% probability that the boundary will reach as far as the Flathead Valley by day break. This boundary will continue tracking through western Montana and Lemhi County through Friday evening, as a digging shortwave trough within northerly flow pulls colder air across the divide.

Forecast guidance has trended colder for Sunday into Monday, with an increasing risk of dangerous wind chills ranging from -10F to -20F across western Montana and -30F or colder along the divide. A stronger push of arctic air is expected Sunday afternoon through Monday morning. The center of the arctic high has shifted westward, and ensemble forecasts now indicate a 50% probability of a 1050mb surface high along the divide by Monday morning. This arctic high will be particularly strong, with the last occurrence of a 1050mb high in Great Falls happening during the December 22, 2022, arctic event. During that event, Butte reached -40F, Kalispell -34F, and Missoula -19F, while single-digit temperatures were recorded in the lowest elevations of north-central Idaho.

Given the forecast trends and historical analogs, temperatures along the divide, including the I-90 and Highway 200 corridors east of Missoula, have been lowered, with greater confidence that lows could reach -20F or colder. These extreme temperatures will bring elevated risks for hypothermia, as well as impacts to outdoor recreation and agriculture interests. /AL
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