textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Minimal impact from light snow showers this morning, again tonight/Saturday morning.

- Strong Winds Sunday into Monday, with a 60 to 80 percent chance of widespread gusts over 40 mph in the valleys.

- Active Pattern for the rest of next week/weekend; potential for more wind and winter weather impacts.

Scattered light snow showers continue this morning within a northwest flow, primarily south of the I-90 corridor. These showers are producing brief accumulations on mountain passes, while patchy dense valley fog is a concern across northwest Montana. Aside from lingering terrain- based showers, today will feature a mix of sun and clouds with seasonable temperatures.

A weak disturbance, carrying residual moisture from a decaying atmospheric river, will arrive late this evening and persist through Saturday morning. This system is expected to bring 1-2 inches of snow to the ID/MT border passes. Valley impacts remain negligible, with only light, isolated showers anticipated.

Confidence is high for a transition to a more impactful weather pattern starting Sunday. A atmospheric river will target northwest Montana before shifting southward as a potent cold front crosses the region on Monday. While this front will eventually lower snow levels to valley floors, wind remains the primary hazard.

Ensemble guidance has trended upward, showing a 60-80% probability of valley gusts exceeding 40 mph across western Montana. In north-central Idaho, these higher probabilities are currently focused on the Grangeville area (70%). Furthermore, a favorable synoptic setup for mountain wave activity suggests localized gusts over 50 mph are possible from Sunday morning through Monday morning. Wind highlights are likely in upcoming shifts, as concerns grow regarding difficult travel for high- profile vehicles, potential tree damage, and localized power outages.

The active pattern is projected to persist through late next week into next weekend (March 14-15) as additional weak-to-moderate atmospheric rivers reach the Northern Rockies. The Climate Prediction Center (CPC) guidance for March 13-15 highlights a 20-40% chance of both high winds and heavy snow. While significant model variance regarding snow levels limits specific valley accumulation forecasts at this range, the period requires close monitoring for renewed winter impacts and at least moderate mountain pass travel disruptions.

AVIATION

Drier air is eroding mid-level clouds from north to south, favoring strong radiational cooling. KGPI remains the primary concern for patchy dense valley fog (LIFR) through 06/1600Z.

A few light showers persist south of I-90 in northwest flow, these remain terrain-focused. Expect VFR conditions at all terminals today (aside from morning fog) with light winds, though occasional gusts of 15-20 kts are possible in well-mixed areas.

A weak disturbance arrives after 07/0300Z, bringing moisture from a decaying atmospheric river. Expect increasing mountain obscurations and light precipitation through Saturday morning. Impact to terminal flight categories is expected to be minimal, though MVFR ceilings may develop near the ID/MT border.

MSO WATCHES/WARNINGS/ADVISORIES

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