textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Easterly gap winds during the overnights through Sunday morning: choppy lakes and strong canyon winds.

- Widespread rain and mountain snow above 7,000 feet late Saturday night, through Sunday, into Monday.

- Drying and warming conditions by mid-week.

Isolated showers will continue over high terrain east of Highway 93 this afternoon before diminishing. An easterly surface pressure gradient will build tonight and persist through Sunday morning, generating east-to-northeast wind gusts toward 30 mph through favored canyons, on the west slopes of major mountain ranges, and on regional lakes including Flathead Lake. Saturday through the early evening will remain mostly dry and slightly warmer than Friday ahead of the main incoming system.

A closed upper-level low tracking across the region will push widespread showers and embedded thunderstorms from west to east starting after midnight Saturday night and continuing through Sunday. Recent model guidance has shifted the low track slightly farther north, also slightly increasing precipitation forecasts across north- central Idaho and northwest Montana where 0.50 to 1.25 inches of rainfall is expected. Southwest Montana will remain on the drier periphery and within a fetch of elevated west and southwest winds, again fostering near-critical fire weather conditions based solely off of RH and winds. Snow levels drop to around 7,000 feet Sunday into Monday morning, creating wet, cold, and raw conditions in the backcountry increasing the risk for hypothermia to those who are unprepared.

The low exits east by Tuesday, yielding to a split-flow pattern aloft by mid-week. Temperatures will rebound toward and above seasonal averages alongside a general drying trend, though minor embedded disturbances will maintain low-end shower chances.

AVIATION

VFR flight categories will prevail across regional terminals through Saturday afternoon. However, isolated thunderstorms are possible near KGPI between 11/2100Z and 12/0100Z, capable of brief reductions in local visibility due to light rain. An easterly surface pressure gradient will develop this evening between 12/0100Z and 12/0600Z across the region, with northeast winds strengthening at KGPI after 12/0800Z with gusts up to 20 knots. This near-surface easterly flow will generate localized turbulence and low-level wind shear downwind of canyon exits into Saturday morning. Widespread rain showers and lowering MVFR/IFR ceilings will arrive from west to east near and after 13/0600Z Saturday night into Sunday.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Fire Weather Watch from Sunday afternoon through Sunday evening for East Beaverhead.

ID...None.