textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Widespread light snowfall Wednesday.

- Pockets of light freezing rain in valleys and snow at pass level are possible later this week.

- February will begin with very mild temperatures.

Temperatures this morning ranged from just below zero to the low teens in western Montana, and into the upper teens in the lower valleys of north-central Idaho. Satellite imagery showed pockets of fog and low clouds across northwest Montana, particularly along Flathead Lake. This fog will continue to lift this afternoon as mid-to-high-level clouds arrive from the northwest. These clouds are expected to remain overnight, which will limit fog redeveloping and keep overnight lows from dropping as cold as this morning. Despite the dry weather, afternoon high temperatures are expected to remain near normal for the next couple of days.

On Wednesday, the ridge of high pressure will weaken, allowing a weak weather disturbance to move south out of Canada. This system will bring widespread light snowfall to most locations across the Northern Rockies. While accumulations will remain limited, isolated slick spots are possible for the Wednesday morning commute. Mountain passes along the Montana/Idaho border, as well as Marias Pass, are expected to see 1 to 3 inches of snow by the end of the day, with a trace to half an inch in the valleys of western Montana. Temperatures in north-central Idaho will be warm enough to limit snow accumulation below 4,000 feet.

Additional waves of moisture will be possible Thursday through Saturday. Forecast models are split, with 50 percent showing a trace to a tenth of an inch of precipitation across northwest Montana and north-central Idaho, while the other half suggests drier conditions. Given the recent cold spell, ground temperatures will remain frozen even if air temperatures rise above freezing. This could create potential for light freezing rain or a wintry mix. Black ice would be the primary impact, especially at night. As winds shift to the west later in the week, many locations could break the inversion and warm well into the 30s and 40s, possibly hitting 50 degrees in a few spots.

Februarys opening act features temperatures in the 40s and 50s, continuing a winter that has leaned far more Pacific than Arctic. Models indicate a strong warming trend with Pacific air flowing into the region.

AVIATION

Clouds will increase from the northwest today. Morning fog and low stratus have improved, and persistent cloud cover overnight is expected to prevent fog from returning. This cloud cover will also keep temperatures from dropping as low as previous mornings. Another dry day is expected Tuesday, with widespread light snowfall returning to the Northern Rockies on Wednesday. Accumulations are expected to be light, with less than half an inch in the valleys.

MSO WATCHES/WARNINGS/ADVISORIES

MT...None. ID...None.