textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Showers, isolated thunderstorms, and cooler temperatures return this weekend. - Increasing potential for widespread precipitation by Wednesday and Thursday next week with a closed low pressure system.

As an upper level trough approaches the region today from the west, increasing breezy conditions are anticipated. The combination of breezy and dry conditions will create elevated fire weather concerns across southwest Montana today and Saturday, so please exercise extreme caution with any open flames or ignition sources.

A cold front will move through the region on Saturday, dropping temperatures by about ten degrees and bringing localized showers and thunderstorms, primarily to northwest Montana and along the Continental Divide. Sunday will feature cooler weather and more widespread but light rain, with minor snow accumulations possible in the mountains above 5,500 feet, particularly south of Interstate 90. For those with sensitive plants or gardens, frost potential develops Sunday and Monday mornings as drier air builds over the region and skies begin to clear. Monday looks like the more widespread day for frost in the lower valleys of western Montana and higher valleys of north central Idaho. However, some frost is also possible across northwest Montana valleys Sunday morning.

By mid-to-late next week, a large weather system is expected to bring significant and widespread precipitation across western Montana and north central Idaho. Ahead of this system, thunderstorms may become more numerous across the region, especially by Tuesday. Most locations have a high probability (60 to 80 percent chance) of receiving over half an inch of rain between Wednesday and Friday. While less likely, this system has a 10 to 20 percent chance of tapping into deeper moisture, potentially bringing one to two inches (or possibly more!) of rain along the Continental Divide. If these heavier amounts materialize, localized flooding could become a concern, especially in recently saturated areas such as the Mission Mountains and surrounding valleys.

AVIATION

VFR conditions will generally prevail today, though an approaching upper-level trough will induce strengthening surface winds and breezy afternoon conditions across all airfields, with gusts up to 20 kts. A cold front sweeping through on Saturday will introduce localized showers and isolated thunderstorms, primarily impacting routes across northwest Montana and along the Continental Divide in southwest Montana, which will lead to brief periods of MVFR conditions and localized mountain obscurations. Flight conditions will further deteriorate on Sunday as widespread light precipitation develops and freezing levels lower to near 5,500 feet MSL, resulting in more extensive mountain obscurations and scattered MVFR ceilings, particularly for higher terrain and passes south of the I-90 corridor.

MSO WATCHES/WARNINGS/ADVISORIES

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