textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Warming trend today through mid week.

- Thunderstorm chances expand northward Tuesday and Wednesday. Gusty outflow winds and lightning as the main concerns.

- Cooler temperatures this weekend, shower/thunderstorm chances continue.

Through Wednesday: High pressure will rebuild across the Northern Rockies today, bringing stable conditions and light winds. Temperatures will trend warmer, peaking around 10 degrees above seasonal norms Tuesday and Wednesday. Air quality may degrade across northwest Montana Tuesday and Wednesday as weak easterly overnight flow transports smoke from the Camp Creek Fire into the region.

Monsoonal moisture will surge northward Tuesday, introducing shower and thunderstorm chances up to the I-90 corridor. Deeper moisture will encompass most of the region Wednesday, expanding storm coverage. A mix of wet and dry thunderstorms will heighten the risk for lightning-initiated fire starts. Strong outflow winds will accompany any activity, with an isolated storm or two potentially producing near-severe gusts (50-60 mph), primarily in southwest Montana on Wednesday.

Thursday through Weekend: Ensemble guidance maintains high confidence (>90%) in a Pacific Northwest trough returning late this week into the weekend. While exact timing and specific impacts remain uncertain, expect moderating temperatures and an uptick in winds over several days, likely opening another window for elevated fire weather. A minority but growing number of ensemble solutions supports a closed-low track, which would yield more widespread precipitation, a trend to monitor.

AVIATION

High pressure rebuilding across the region will maintain widespread VFR conditions into Tuesday, accompanied by light, terrain-driven winds at all terminals. A warming trend through midweek will noticeably elevate density altitudes across regional airfield elevations, impacting aircraft performance. Wildfire smoke will remain the primary driver of localized slant-range visibility degradation. In particular, a light easterly gradient tonight is expected to transport smoke from the Camp Creek Fire into northwest Montana, while overnight drainage flow from the Nature Grove Fire may degrade slant-range visibility near Hamilton (KHRF).

Monsoonal moisture surging northward will bring increasing shower and thunderstorm chances Tuesday into Wednesday. Initial convection Tuesday afternoon will pose a threat for localized, erratic convective outflow winds gusting 20-30 kt. Monsoonal moisture deepens on Wednesday, expanding convective coverage and increasing storm intensity. Outflow winds will trend higher Wednesday afternoon, with isolated cells capable of producing localized severe gusts exceeding 40-50 kt, mainly across southwest Montana.

MSO WATCHES/WARNINGS/ADVISORIES

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