textproduct: Glasgow

KEY MESSAGES

- Active weather will continue is expected through Tuesday with heavy rain possible at times.

- SPC has an enhanced risk of severe thunderstorms today and tonight along the North Dakota border with a slight risk in the middle and marginal risk in the west.

- Temperatures warm starting on Tuesday and get warmer each day through Friday.

DISCUSSION

WEATHER PATTERN OVERVIEW: Upper trough digging into the Pacific Northwest will move east this weekend with a closed low expected over Montana by Sunday night. The trough pattern is expected to be strongest this weekend, which is part of why there is severe weather expected to occur for various parts of the area today and tonight. Lee trough and surface cyclogenesis is currently transporting warm, moist air into Montana in the southeast low level flow. Combined with southwest flow aloft creating vertical shear, forcing and destabilization along the front, there is support for organized severe thunderstorms today. SPC has a marginal risk in the west, slight risk in the center and an enhanced risk for severe weather in the east for today and tonight. There will be uncertainty today in how much low clouds will develop this morning and how long they will last if they do develop. If they don't develop or burn off with surface heating early in the day, severe weather is more likely. If the low clouds develop and stay into the afternoon, it is less likely for severe weather to occur.

High precipitable water and surface dewpoints suggest heavy rain potential in individual storms today. Although storms are expected to move somewhat fast, training of storms is possible, which means that storms may form over the same location more than once. Rain totals often accumulate enough to create rises in creeks and streams temporarily with this type of activity.

The upper low will move over Montana on Sunday and Monday with cool temperatures and frequent showers with thunderstorms at times. Winds will increase on the back side of the system with cold air advection.

With the upper trough moving east by midweek, temperatures will be on the rise into the holiday weekend. Fairly persistent weak trough over the Pacific Northwest will support occasional chances for showers and storm action.

FORECAST CONFIDENCE & DEVIATIONS: Increased surface winds for this evening into tomorrow with the oncoming surface low. The models often struggle with recognizing the strength of the surface spin.

There is moderate confidence of severe weather occurring in the eastern half of the area today, and low confidence on Sunday in the east.

There is moderate confidence in rainfall amounts through Monday and in temperatures climbing above average in early July.

AVIATION

UPDATED: 0600Z

FLIGHT CATEGORY: A mix of VFR and MVFR today and tonight.

DISCUSSION: An upper trough/low is positioning itself over the area through Monday, and strong southwest flow will allow off and on showers and thunderstorms to occur through the weekend. There is moderate confidence of MVFR ceilings for KGGW, KOLF, and KSDY this morning and low confidence at KGDV. Ceilings are expected to lift to VFR levels this afternoon and could return tonight.

WINDS: East at 10 to 20 knots overnight diminishing after 10z this morning. Look for variable wind directions today at 10 knots or less as surface low moves through northeast Montana. West to NW winds 5 to 10 knots are expected between 00z and 06z Sunday with winds becoming SW after 06z Sunday.

GGW WATCHES/WARNINGS/ADVISORIES

Lake Wind Advisory until 4 AM MDT early this morning for Central and Southeast Phillips-Central and Southern Valley-Garfield- McCone-Petroleum.