textproduct: Glasgow

KEY MESSAGES

- Increasing risk for severe thunderstorms today and this evening bringing strong winds, large hail, and heavy rainfall.

- Cold front tonight will bring gusty NW winds on Monday.

- Warm and dry conditions resume Tuesday as the western ridge rebounds.

DISCUSSION

WEATHER PATTERN OVERVIEW: Upper ridge over eastern Montana overnight will move east today while an upper trough moves in from the Pacific NW tonight.

Showers and thunderstorms will move through the forecast area today as the ridge axis moves east and a weak shortwave ahead of the upper trough moves through the ridge. Ample midlevel monsoonal moisture will begin streaming into eastern Montana and with high PWATs possible, some storms could produce heavy rain. The upper trough will knock down the ridge tonight with another round of storms. Strong winds aloft will increase vertical wind shear and coupled with moist, unstable air will bring increased severe risk. Any storms that develop may produce damaging winds and large hail. All thunderstorms have lightning, which may pose a risk of fire starts. Gusty southeast winds overnight will diminish this morning which will allow the Lake Wind Advisory to expire 3 AM.

Cold front moves through the area tonight and will bring gusty NW winds on Monday with cooler temperatures. A Lake Wind Advisory may be needed for Fort Peck Lake on Monday.

Ridge rebounds starting on Tuesday in the wake of the departing trough to bring dry conditions with temperatures slightly above normal.

FORECAST CONFIDENCE & DEVIATIONS: Made tweaks to PoPs and thunder chances today and tonight. No other changes to NBM. Confidence for storm chances is high today and tonight, though timing, severity and exact location of strongest storms remains uncertain.

AVIATION

UPDATED: 0600Z

FLIGHT CONDITION: VFR most of the time. areas of MVFR to IFR in stronger storms.

DISCUSSION: Varying amounts of mid and high clouds are expected today and tonight. Showers and isolated thunderstorms move east across the region this morning. A break in the storms is expected this afternoon. After 00z this evening, scattered shower and thunderstorms will move east through the area tonight. Some storms today and tonight could become severe with large hail and wind gusts to 50 knots.

WINDS: East to SE at 5 to 15 knots most of today becoming variable late this afternoon and remaining variable at 10 knots or less tonight. Any thunderstorm that passes over TAF sites could have strong, erratic wind gusts.

GGW WATCHES/WARNINGS/ADVISORIES

Lake Wind Advisory until 3 AM MDT early this morning for Central and Southeast Phillips-Central and Southern Valley-Garfield- McCone-Petroleum.