textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Dry weather will continue through early next week (January 20)

- Pattern change for the latter part of the week (January 22-24)

Stable conditions will continue across the Northern Rockies for the next couple of days. Fog is still anticipated to hold on strong across the valleys of north central Idaho and extreme northwest Montana. As temperatures drop below freezing during the overnight hours in these foggy conditions expect some light ice formation on hard surfaces including paved roadways.

A subtle disturbance is expected to move across the region on Sunday which should help lift and potentially dissipate the fog and low stratus especially across western Montana. North central Idaho will probably remain stuck under the fog and low stratus.

The models are still trending towards a pattern change by the latter part of the work week. A glancing push of arctic air is expected on Wednesday which will bring in cooler temperatures and help break up the valley inversions, but precipitation will be limited. A more significant change in the pattern appears to be on course for Friday as another push of artic air moves into the Northern Rockies along with a potential fetch of moisture causing widespread snow. The timing of the arctic front along with the extent of the moisture is still uncertain at this time, but residents of the Northern Rockies should start preparing for winter conditions by the weekend.

AVIATION

Stable conditions will remain over the Northern Rockies for the next 24 hours. Fog and low stratus continue to impact the valleys of north central Idaho and extreme northwest Montana. KSMN will have difficult improving its visibility today. KGPI and KMSO are anticipated to have vicinity fog that could move over the terminals for a short period of time.

MSO WATCHES/WARNINGS/ADVISORIES

MT...ID...Air Stagnation Advisory until 4 PM PST Tuesday for Northern Clearwater Mountains...Orofino/Grangeville Region... Southern Clearwater Mountains.