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DISCUSSION

KEY MESSAGES:

1) Haze and smoke will continue to be problematic at times through at least Thursday.

2) Active weather is expected the next several days with varying amounts of showers and thunderstorms. A few storms this afternoon and tonight could become severe mainly south of the Missouri River.

WEATHER PATTERN OVERVIEW:

Smoke from several different Canadian wildfires has brought poor air quality and visibility as low as 1.75 miles to the forecast area overnight. HRRR smoke model keeps this smoke over NE Montana in varying concentrations into at least Thursday.

Quasi-stationary front will be near Great Falls, Lewistown and Billing today and tonight. Tight surface gradient to the east of the front will bring strong enough east winds today and tonight for a Lake Wind Advisory for Fort Peck Lake. There will be chances for showers and thunderstorms at times today with somewhat unstable atmosphere over the forecast area. The atmosphere will become more unstable this afternoon over the southern zones and a strong shortwave trough moves into the area tonight increasing the chances for showers and thunderstorms. The models have this wave moving through NE Montana during the day on Thursday with widespread showers and isolated thunderstorms.

This evening, updraft helicity again shows best coverage for isolated stronger storms affecting central and southern Montana. SPC currently has a marginal risk for severe storms mainly south of the Missouri River with the main threat being strong winds.

While the wave exits the forecast area Thursday night, a moist and unstable SW flow aloft will continue for the next several days with frequent chances for showers and thunderstorms continuing.

FORECAST CONFIDENCE & DEVIATIONS:

Confidence remains high for smoke continuing into Thursday.

Low confidence today for chances of showers and thunderstorms with higher confidence for precipitation for tonight and Thursday. Low confidence on rainfall amounts as it will depend on the timing and exact placement of thunderstorms and thus heaviest rainfall amounts.

No deviations from the NBM at this time.

AVIATION

Updated: 0815Z on June 11.

With varying concentrations of smoke over the area, visibility will vary from VFR to IFR today and tonight. There will be varying amounts of mid and high clouds over the area today and this evening with isolated showers and thunderstorms. Widespread showers and isolated thunderstorms will move into the area from the SW late tonight and continue during the day on Thursday. Widespread MVFR/IFR conditions will develop late tonight into Thursday morning with low clouds and rain reducing visibility. Look for east winds today at 10 to 20 kts in most areas and 15 to 25 knots around KGGW and east winds 10 to 20 knots tonight.

GGW WATCHES/WARNINGS/ADVISORIES

Lake Wind Advisory until 6 AM MDT Thursday for Central and Southeast Phillips-Central and Southern Valley-Garfield-McCone- Petroleum.