textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- High temperatures will peak on Tuesday, with many valleys reaching the mid 50s with a few spots over 60.

- A Pacific trough will arrive Wednesday morning, bringing widespread rain and mountain snow, followed by much cooler temperatures and gusty winds through Thursday.

Expect occasional light rain and high-elevation snow showers across southern Idaho County and Lemhi County today. Mountains accumulations will be light (generally less than 1-2 inch). Most of western Montana and north-central Idaho will enjoy a dry, mild day with high temperatures in the upper 40s to low 50s. Skies will stay mostly sunny for the northern valleys, while some lingering mid-level clouds may persist across Lemhi County and the southern Bitterroot.

Tuesday will likely be the warmest day of the week as the ridge of high pressure reaches its peak strength. Expect plenty of sunshine through the afternoon, allowing valley temperatures to climb into the mid-50s to low 60s in some locations. By Tuesday evening, clouds will thicken from the west ahead of an approaching Pacific system.

A Pacific trough is projected to cross the region during the middle of the week, and there is high confidence (80%+) in widespread rain and mountain snow starting Wednesday morning. Initially, snow levels will be quite high (around 5,000 feet) on Wednesday before dropping toward valley floors by Thursday morning as cooler air filters in. There is medium uncertainty regarding the snow levels for the Thursday morning transition. Model solutions differ on the speed and strength of the incoming cold air; a faster cold front could result in a slushy morning commute for the valleys, while a slower arrival would keep impacts restricted to the mountain passes.

Westerly winds will become gusty behind the cold front, particularly along the Continental Divide and through the Butte/Blackfoot region.

Friday into Next Weekend: The region stays in a cooler, unsettled northwest flow. Scattered snow showers will continue, primarily focused over the mountains. We are also keeping a very close eye on the March 9-11 period, as long-range ensembles continue to hint (20-30% chance) at a potentially much colder weather system. If this verifies, we could see a drastic shift back to winter-like temperatures and valley snow.

AVIATION

VFR conditions will prevail for most of north-central Idaho and western Montana through the next 24 hours with light, terrain- driven surface winds. While some high-level cirrus will drift over the region, ceilings will remain well above impact thresholds. However, KSMN and southern ranges will continue to see moisture from a southern-stream system lead to deteriorating conditions today. Expect lowered ceilings (MVFR) and scattered rain/snow showers through this afternoon. Terrain will be frequently obscured across southern Idaho County and the Lemhi/Bitterroot ranges due to low clouds and precipitation. Conditions should begin to improve after 03z Tuesday as the moisture exits to the southeast.

MSO WATCHES/WARNINGS/ADVISORIES

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