textproduct: Glasgow

KEY MESSAGES

- Scattered rain showers and isolated thunderstorms with a marginal risk for severe outflow winds tonight.

- Seasonable temperatures and widespread rain showers are expected Sunday night and Monday.

- Much below normal temperatures with significant mixed precipitation is becoming more likely for Thursday and Friday.

DISCUSSION

WEATHER PATTERN OVERVIEW:

Warmth under an upper ridge pushing to the east has produced steep lapse rates and mixing ahead of increasing instability and shear, with a shortwave trough and cold frontal passage this evening. While not aided by elevated synoptic winds like earlier this week, the setup is prime for at least a few 50-60 mph gusts from outflow of any showers and thunderstorms that develop, especially over Phillips and Petroleum counties this evening.

Beginning Sunday evening, an upper low to the west transitions into an open trough and the SW flow aloft brings more moisture into Montana, producing widespread showers with a slight chance of thunderstorms Sunday night and Monday. Models and ensembles still differ on how quickly to move the upper trough through the forecast area. At this point, the NBM lingers chances for showers through Tuesday in some areas.

The next system will bring chances for showers beginning either Wednesday afternoon or evening with colder temperatures starting on Thursday. This will introduce chances for accumulating snow, particularly for elevated areas Thursday night. Chances for at least 2" of snow at this time are 20-40%.

FORECAST CONFIDENCE & DEVIATIONS:

The only deviations made were slight adjustments to winds mixing in the best agreement from hi-res model data and an increase in thunder probability for this evening to reflect a widespread slight chance.

There is moderate or average confidence in temperatures through the week. While there is moderate to high confidence in two systems producing wetting precipitation, confidence is generally low for widespread accumulating snow to occur later in the week.

-JEZ

AVIATION

LAST UPDATE: 1830Z, Saturday, April 11

FLIGHT CAT RANGE: Mostly VFR to MVFR

DISCUSSION: High and mid level clouds are increasing this afternoon. Scattered showers and isolated thunderstorms will move from SW to NE this evening. KGGW and points west are the most favorable areas for a thunderstorm with strong downburst wind gusts between 00-03Z, while other sites may need an amendment for gustier winds in the vicinity of showers.

LLWS: Pockets of wind shear between 04-08Z tonight with west wind 40 to 50 knots within 2000 feet AGL.

GGW WATCHES/WARNINGS/ADVISORIES

None.