textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- A warm front will clip north-central Idaho and southwest Montana this afternoon through Monday morning, bringing light rain and mountain snow showers.

- High pressure peaks on Tuesday, likely resulting in the warmest temperatures of the week with many valleys reaching the mid 50s.

- A Pacific trough arrives Wednesday, ushering in cooler air and widespread rain and snow showers through Thursday.

An upper-level ridge is currently providing dry conditions and light winds for much of western Montana. However, ensemble models have converged on a solution showers clipping north-central Idaho, Lemhi County, and southwest Montana starting this afternoon. Expect light rain in the valleys (like the Salmon and Clearwater) and light snow for the mountains (Lost Trail Pass). Valleys like Missoula and Kalispell will likely remain dry with just an increase in mid-level clouds. Highs today will reach the 40s and low 50s under mostly clear skies in the north.

The ridge of high pressure will reach its maximum strength on Tuesday. This will likely be the warmest day of the week for the entire region. Clouds will begin to thicken late in the evening ahead of the next system.

A transient Pacific trough is projected to cross the Northern Rockies on Wednesday and Thursday. There is high confidence (85% agreement) that this system will bring widespread rain and snow showers. Initially, snow levels will be quite high (around 5,000 feet) on Wednesday, but will drop toward valley floors by Thursday morning as cooler air filters in. Breezy westerly winds will re- emerge, particularly along the Continental Divide and terrain- exposed locations like the Butte area.

Unsettled northwest flow will persist for the rest of the week and into the weekend, and passing disturbances will maintain hit- or-miss snow showers in the mountains.

Long Range: We continue to monitor teleconnections for a potential Arctic intrusion during the second week of March. While confidence in timing is low, the potential exists for beneficial mountain snow and periods of valley rain and snow.

AVIATION

VFR conditions will prevail at all regional terminals (KMSO, KGPI, KBTM, KSMN, KHRF) through the next 24 hours. High pressure will maintain light, terrain-driven surface winds and high-level cirrus. Patchy fog is possible in the more sheltered valleys of north-central Idaho and northwest Montana, though terminal- specific impacts are not anticipated. This afternoon, a clipping warm front will increase mid-level cloud decks across north- central Idaho and southwest Montana. Localized MVFR is possible near KSMN as light rain and mountain snow showers develop.

MSO WATCHES/WARNINGS/ADVISORIES

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