textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Unseasonably warm, dry, and windy today bringing elevated fire weather concerns especially across southwest Montana.

- Light rain continues today for northwest Montana

- Cold front passage on Saturday will bring increased winds, a chance for precipitation, and a return to more seasonal temperatures.

The Northern Rockies remain positioned on the southern periphery of an upper-level ridge within a progressive, unseasonably warm southwesterly flow. An atmospheric river remains focused into southern Canada, though peripheral moisture will continue to clip northwest Montana today. In contrast, the remainder of western Montana and north-central Idaho will experience dry conditions and breezy westerly winds. The most critical combination of warm and dry conditions will once again impact areas south of the I-90 corridor, particularly across southwest Montana and Lemhi County, where 25 to 35 mph gusts will overlap with the warmest and driest boundary layer conditions.

Persistent precipitation continues today across northwest Montana, where liquid totals over the last 12 hours have ranged from nominal valley amounts to over 0.50 inches in the high terrain. High-resolution guidance suggests a 30 to 50% probability of an additional 0.50 inches of rainfall through Saturday morning, primarily favored north of the Highway 2 corridor. The combination of rain-on-snow and unseasonal warmth maintains a risk for localized rock and debris slides in unstable terrain. While area rivers will see steady rises, current hydrologic forecasts keep stages below action levels.

A cold front will move through the region on Saturday, bringing breezy conditions in the afternoon. This boundary will trigger a period of light to moderate convective showers. Post-frontal cold advection will return temperatures to near-seasonal averages by Saturday night. Light snow is possible following the front, though no significant accumulations or travel impacts are anticipated. A brief drying trend follows for the remainder of the weekend before a more robust Pacific system introduces widespread wind and precipitation chances Tuesday into Wednesday.

AVIATION

Predominant VFR conditions will continue for most terminals south of the I-90 corridor (including KMSO, KBTM, and KSMN) through the next 24 hours. While mid-to-high level cloud decks will persist, ceilings are expected to remain above 5,000 ft AGL. The primary aviation concern for these southern sites remains breezy westerly surface winds, with gusts of 25 to 30 kt expected during the afternoon hours. As surface winds decouple after 21/03Z, lingering 35 to 40 kt southwesterly flow at ridgetop levels will introduce a risk for localized low-level wind shear (LLWS) and mechanical turbulence, particularly at KBTM and KHRF.

Across northwest Montana, including KGPI, an active moisture plume will maintain lower flight categories. Periodic light rain will result in occasional MVFR ceilings and visibility through Saturday morning. High-terrain obscuration will be frequent as peripheral moisture interacts with the higher terrain.

MSO WATCHES/WARNINGS/ADVISORIES

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