textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Today and Thursday will be the warmest days before the change back to fall-like weather.

- Choppy lake conditions on lakes for Thursday due to westerly winds between 15 and 25 mph, and locally higher speeds expected over the Divide.

- Stiff northeast winds are possible Friday night through Saturday creating choppy conditions on area lakes.

- Cutoff Low brings widespread rain, with snow above 6000 feet Saturday night into Sunday.

Northwesterly flow aloft behind a departing trough of low pressure will keep near-normal daytime high temperatures in the forecast for this afternoon. Expect clear skies across the Northern Rockies today and tonight. Upper level flow flattens out, becoming more westerly on Thursday as a broad trough of low pressure moves along the Canadian border. There will be enough moisture involved to keep some chances for precipitation in the forecast for northwest Montana in the morning. Elsewhere, Thursday looks warm and dry with increased westerly winds. Winds will be gusty enough to create choppy conditions on Flathead lake and elevated fire weather concerns for southwest Montana.

By Thursday night, a weak front will become the impetus for showers that continue throughout the day Friday. Northeast winds develop by Friday evening which will enhance shower activity over the Glacier Region, and also could cause Lake MacDonald to become choppy.

An impressive pressure gradient sets up on Saturday in response to the incoming low pressure system moving onshore over Oregon. There is a 50% chance that sustained winds could exceed 15 mph and gusts exceed 25 mph over Flathead Lake. Other areas, especially channeled locations could also experience elevated winds.

A cut-off low pressure system will track from southwest Idaho Saturday night to east of Great Falls by Sunday evening, bringing widespread light to moderate precipitation to central Idaho and western Montana. The heaviest precipitation will be roughly 100 miles north and south from a line from Grangeville, Idaho to Missoula to Great Falls with a range from 0.60" to 1.60" of total precipitation. The mountains within this line could receive 1 to 2 inches. This upper trough is a bit colder than the recent system, so snow levels could fall to around 6000 feet by daybreak Sunday morning. It could feel very wintry in the backcountry, especially along the Continental Divide and in Glacier National Park. A moderating and drying trend is expected by early next week.

AVIATION

VFR conditions and light diurnally driven winds continue into this evening. Patchy valley fog is once again possible on Thursday morning but less coverage than experienced this morning. High and mid level clouds increase from the northwest on Thursday with a few light showers in northwest Montana. Westerly winds also pick up with gusts of 20-30 kts on Thursday afternoon.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Red Flag Warning from noon to 9 PM MDT Thursday for East Beaverhead.

ID...None.