textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Cold mornings with valley fog for much of the rest of the week.

- A warming trend for high temperatures through the end of the week with Friday 10 to 15 degrees above average.

- Cold front coming this weekend brings gusty winds to northwest MT on Saturday.

High pressure slowly builds over the Northern Rockies, while low pressure develops over Southern California. This is a blocking pattern and will slow the progression of weather systems from west to east. Expect continued cool to cold mornings with patchy fog, especially along river valleys. Afternoon high temperatures slowly warm to the low 70s by Friday in western MT, or what is the average high for the 3rd week of September. Enjoy a small return to late summer.

Saturday a mostly dry, cold front breaks down the ridge and 'blocking pattern'. Expect a very breezy afternoon, especially north of I-90. Winds in the high terrain could gust 40 to 50 mph, while valleys experience gusts 20 to 30 mph. Humidities remain in the 30s, please exercise caution with any fall burning.

The pattern is expected to remain progressive to start next week, with greatly varying model outcomes. There remains many questions about how far south the next trough digs, how cold the associated air mass will be, and how much moisture is available for precipitation. More to come.

AVIATION

A ridge over the region is causing VFR conditions over the region during the day, but allowing some valley fog to develop at night. Terminals most likely to be affected by fog are KGPI and KMSO, though there's a chance for KSMN as well.

MSO WATCHES/WARNINGS/ADVISORIES

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