textproduct: Glasgow

KEY MESSAGES

- Lake Wind Advisory is in effect from 3 PM today to midnight tonight for Fort Peck Lake.

- Brief chance for rain this evening, with little to no accumulation expected.

- Breezy conditions on Monday and Tuesday with warm temperatures on Tuesday, followed by a chance for precipitation Tuesday night. Below average temperatures late in the week.

DISCUSSION

WEATHER PATTERN OVERVIEW: Northeast Montana is between an upper trough and upper ridge pattern, so this unstable zone is helping maintain some low to mid level clouds over the area. A shortwave trough is expected to graze the eastern part of the area this evening, and light rainfall may occur as this disturbance moves through. Most amounts are expected to remain below 0.03 inches.

The GFS ensemble suggests frontogenesis will occur with a shortwave trough over British Columbia on Monday. As this approaches, southeast winds on Monday are expected to crank up to 15 to 25 knots, followed by a warmup on Tuesday with strong northwest winds. This shortwave trough is expected to bring an opportunity for rain and snow showers on Tuesday night, as well as a drop in temperatures. Recent trends have indicated a wetting rain is expected across the northeast part of the area, but there is high uncertainty on this prediction.

There are precipitation chances that linger after Tuesday night, but there is high uncertainty about timing and location of any shortwave troughs or cold fronts. Temperatures are expected to slowly climb back to around normal for this time of year.

FORECAST CONFIDENCE & DEVIATIONS: Main deviations were for winds and PoPs. Increased winds to NBM 90 for most of the area for the shortwave trough passage this evening, and above NBM90 for Fort Peck Lake. Increased PoPs for the trough passage this evening, and manually to a chance PoPs tomorrow.

There is high confidence of a shortwave trough moving through the area tonight, and moderate confidence in precipitation occurring through midnight.

There is low to moderate confidence in precipitation occurring tomorrow.

There is moderate to high confidence in winds on Monday and Tuesday, with high confidence in temperatures through Wednesday.

There is moderate confidence in accumulating precipitation occurring with the shortwave trough on Tuesday afternoon into Wednesday.

There is low confidence in precipitation amounts beyond Wednesday.

There is moderate confidence in stress to newborn livestock as wind chill temperatures have potential to reach the single digits on Wednesday night.

AVIATION

LAST UPDATE: 1900Z

FLIGHT CAT RANGE: Scattered MVFR through 09Z Sunday, then VFR through 12Z, then isolated MVFR through 18Z Sunday, then VFR.

DISCUSSION: A weak trough pattern is allowing cloud cover to persist across TAF sites. A weak shortwave trough is forecast to move through the area this evening, so there is moderate confidence of rain showers and a brief increase in winds with this activity to contribute to MVFR conditions. An overall trough in northwest North Dakota has potential to push southwestward into Montana. This pattern brings moderate confidence of MVFR ceilings occurring on Sunday morning again, but this is expected to only last for a few hours.

WIND: West northwest winds 7 to 17 knots, becoming northwest at 10 to 20 knots between 00Z and 06Z, becoming north northwest at 6 to 12 knots after 06Z.

GGW WATCHES/WARNINGS/ADVISORIES

Lake Wind Advisory until midnight MDT tonight for Central and Southeast Phillips-Central and Southern Valley-Garfield-McCone- Petroleum.