textproduct: Glasgow

KEY MESSAGES

- Areas of rain beginning tonight lasting through Tuesday. Low end chances for seeing a weak thunderstorm tonight. A Lake Wind Advisory is in effect from 9 PM tonight through 9 AM Sunday.

- Overnight temperatures Sunday and Monday are expected to be near freezing.

- Isolated to scattered thunderstorms on Wednesday afternoon.

DISCUSSION

WEATHER PATTERN OVERVIEW:

Upper troughing over much of the western CONUS will bring well below normal temperatures and areas of precipitation through the beginning of the work week. Precipitation will begin to push east into eastern MT around 6 PM this afternoon and continue through Monday night. There is decent chance windy conditions may overlap with a dry slot over southeastern zones tonight into tomorrow morning. The 12Z GFS from yesterday and 12Z GFS ensemble from today continue to show a dry slot setting up over the central part of the area tonight, sort in the shape of an upside down U. Prairie, Garfield, Western Roosevelt, and McCone counties are the most likely places to see the dry slot, so precipitation amounts are below one tenth in that area through Tuesday. For all other counties, the most likely range of total rainfall is one tenth to around a half an inch. There is less than one inch of snow forecast to accumulate in southwest Phillips county through Tuesday, and in the far northern parts of the area.

While thunderstorms are unlikely with this system, there is a 10 to 15 percent chance for thunder tonight. As the low pressure moves in, some CAMs indicate wind gusts exceeding 50 mph in the far southeast tonight.

The upper trough will continue to remain over the area after Tuesday, although a bit weaker than this weekend. This will likely allow shortwave troughs to sneak through the overall flow, bringing some isolated thunderstorm action to the area. The next chance for thunderstorms appears to be Wednesday. Who's ready for a rollercoaster??

FORECAST CONFIDENCE & DEVIATIONS: Made a deviation to the base forecast in the far southeast part of the area tonight by increasing winds manually based on CAM models.

There is high (80 percent) confidence in the Lake Wind Advisory for Fort Peck Lake for tonight.

There is moderate to high (50 to 70 percent) confidence in total rainfall amounts through Tuesday.

There is moderate confidence that any snow that falls in the north and far west will remain below one inch of accumulation.

There is low to moderate confidence in scattered thunderstorms occurring on Wednesday afternoon.

AVIATION

LAST UPDATED: 1830Z

FLIGHT CAT RANGE: VFR today, MVFR tonight

DISCUSSION: Scattered high clouds with a few isolated showers. Clouds will continue to increase toward overcast as a majority of the precipitation begins to push east over TAF sites after 0Z Sunday. The chance of seeing a weak thunderstorm is 10 to 15 percent, opted to leave it out of TAFs at this time.

WINDS: For KSDY, KGDV, and KOLF, east winds 10 to 20 mph with gusts to 30 mph, becoming north northeast after 12Z. For KGGW, southeast at 10 to 20 with gusts to 30 mph, becoming north after 4Z.

GGW WATCHES/WARNINGS/ADVISORIES

Lake Wind Advisory from 9 PM this evening to 9 AM MDT Sunday for Central and Southeast Phillips-Central and Southern Valley- Garfield-McCone-Petroleum.