textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Tonight/Wednesday: Pass level snow, potential minor travel impacts.

- Wednesday night/Thursday: Strong cold front with snow levels to valley floors but light valley accumulations. Moderate pass level travel impacts continue. Snow squall potential in Southwest Montana.

- Next Weekend: Warmer and drier.

Today through Wednesday Morning: A broad, disorganized upper-level trough remains over the region early this morning, producing light remnant showers. Expect a mostly dry day for most populated areas with seasonable temperatures, meanwhile occasional showers continue on the terrain. Breezy southwest winds will develop this afternoon, with gusts reaching 25 mph.

The next plume of Pacific moisture will begin moving into the Northern Rockies this evening and continue through Wednesday ahead of an approaching low-pressure system. The heaviest precipitation is expected to focus across north-central Idaho into northwest Montana. Snow levels will hover near 4,500 feet, keeping most snow impacts confined to the higher terrain. While Lookout, Marias, and Lolo passes will likely (60-80% chance) receive a few inches of new snow, accumulations on roadways are expected to be primarily restricted to pass elevations, quickly turning to wet roads just below pass levels.

Midweek Cold Front & Snow Squall Potential Wednesday Afternoon- Thursday: A strong cold front associated with the low- pressure system will sweep through the Northern Rockies late Wednesday afternoon and evening. This front will increase precipitation intensity while causing snow levels to drop rapidly. Current model guidance indicates the bulk of the moisture will focus along the frontal boundary.

Travelers should be alert for potential snow squalls as the front moves through southwest Montana Wednesday evening. Rapidly deteriorating visibility and slick roads should create moderate travel impacts on mountain passes Wednesday night and Thursday morning. While the strongest dynamics for a prolonged event appear to stay north of our area, wrap-around moisture may impact Glacier National Park through Thursday. There continues to be a minor chance (25%) for a weak closed low to develop over Southwest Montana, enhancing precipitation there, something watch. Widespread shower activity is expected across the region Thursday; valley locations will likely see snow showers, but accumulations will be minimal. High elevations should see light additional accumulations through Friday under northwest flow.

The Weekend & Beyond: A ridge of high pressure will shift over the region this weekend, ushering in a warming and drying trend. This reprieve will be short-lived, however, as the next weather disturbance is projected (by 80% of ensemble clusters) to arrive by early next week.

AVIATION

A broad upper trough remains overhead early this morning with some light remnant showers and mountain obscurations ongoing. VFR conditions will be common at terminals today as ceilings lift but some mountain obscurations will continue, especially across Northwest Montana. Southwest winds will pick up to 10-15 kts with gusts of 20-25 kts at terminal sites this afternoon. Winds will diminish in most valleys from I-90 southward by sunset, but remain elevated in northwest Montana valleys. As precipitation increases tonight, elevated ridgetop winds may occasionally impact terminal sites.

Speaking of precipitation, rain/snow will quickly increase along the ID/MT border by early evening and spread eastward overnight. Precipitation in Western Montana valleys will often be lacking because of downsloping conditions. Snow levels will range from 4000-5000 feet by Wednesday morning.

MSO WATCHES/WARNINGS/ADVISORIES

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