textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Cool, breezy and wet conditions Tuesday through Wednesday

- Another frost possible Thursday morning, especially along and south of the Interstate 90 corridor

An incoming weather system from the Pacific Northwest will bring increasing clouds through this afternoon. By this evening, rain falling from these clouds may initially evaporate before reaching the surface, a process that can produce sudden, gusty winds of 30 to 40 mph. Rain will eventually reach the ground and become widespread overnight into Tuesday morning, with periods of showers and scattered thunderstorms continuing through Wednesday. The heaviest precipitation is forecast across north-central Idaho and along the Continental Divide in northwest Montana, where a half- inch or more of rain is highly likely (80 to 90 percent chance). The broader western Montana valleys will experience lighter rainfall amounts due to the rain-shadowing effect of the surrounding mountains, though localized areas could see heavier amounts under stronger showers or thunderstorms.

In addition to the rain, breezy winds of 25 to 35 mph and noticeably cooler temperatures will create raw, cold conditions in the higher elevations. Backcountry recreationists should be prepared for winter-like weather, as snow levels are expected to drop to roughly 6,000 to 6,500 feet by Wednesday morning, bringing the potential for 1 to 2 inches of snow accumulation. In addition, area lakes will see choppy conditions.

Forecast models indicate a drier trend for Thursday. However, clearing skies will bring the potential for frosty conditions Thursday morning, especially for locations along and south of the Interstate 90 corridor. Moving into Friday and the upcoming weekend, unsettled weather is expected to linger across the Northern Rockies. While the exact timing and intensity of individual weather disturbances remain uncertain, a weak cold front dropping from the north will keep temperatures near seasonal averages. Periodic chances for showers will also persist, primarily across western Montana, with relatively drier conditions expected across north-central Idaho.

AVIATION

Clouds will be increasing from west to east today. A southerly gradient has developed across the region and southerly gusts 15 to 25 kts will be possible at KGPI, KHRF, and KBTM. After 09/0900z light precipitation will develop at area terminals. While visibility will likely remain MVFR or higher, lowered ceilings are expected from drizzle or light rain showers.

MSO WATCHES/WARNINGS/ADVISORIES

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