textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Light snowfall Wednesday, especially through north central Idaho.

- Pockets of light freezing rain in valleys and snow at pass level are possible Thursday into Friday, especially in the mornings.

- Mild temperatures expected for the beginning of February.

High pressure over western Montana and north central Idaho will begin to break down tonight in advance of a weak weather system. Showers will spread first into north central Idaho Wednesday morning, then into western Montana by afternoon. Enough forcing with this system exists to produce some light snow accumulations through primarily north central Idaho down to roughly 2500 feet, impacting portions of the Highway 12 corridor. There is a 60 to 80 percent chance of seeing at least an inch of snow for locations such as Lolo Pass, Lookout Pass and in the higher terrain, however lower elevations most likely will see half of an inch or less. Though generally light, slick spots are a possibility during the morning commute.

Although weak high pressure begins to build back into the region Thursday into Friday, additional waves of moisture are anticipated to move through the ridge, bringing periods of showers to northwest Montana and north central Idaho in particular. Snow levels will likely begin to rise during this timeframe, especially Thursday night into Friday. As this occurs a period of mixed precipitation (including light freezing rain) will be possible in valleys. This overall looks like a light event, but it only takes a tiny bit of ice to make things slick, especially over bridges/overpasses. Showers will be decreasing on Saturday and many valleys will be much warmer than average for this time of year!

High pressure looks to be the dominant feature over the western US for much of next week, which is well represented by virtually all ensemble model solutions through at least day 9 (Feb 5th). Mild conditions are anticipated, though valley inversions may strengthen with the ridge in the later part of next week. Forecast models do show a weak disturbance moving through the ridge on Monday, which will briefly increase cloud cover and bring some light snow to mountain passes.

AVIATION

VFR conditions with dry weather is expected through tonight. Despite a weak ridge of high pressure, increasing clod cover and relatively dry conditions in the lower levels should keep fog formation at bay. A weak wave will bring light snowfall across north-central Idaho generally after 28/1200Z, then transition to mountain snow showers by the afternoon across the remainder of the region. Increasing winds near ridge top levels to around 35kts may lead to some increased mechanical turbulence, particularly after 28/1800z.

MSO WATCHES/WARNINGS/ADVISORIES

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