textproduct: Glasgow

KEY MESSAGES

- Dangerous heat will continue in the SE today and Wednesday with an Extreme Heat Warning for Richland, Dawson, Prairie and Wibaux Counties through Wednesday night. Will have an Heat Advisory for most of the remainder of NE Montana through 2 am Wednesday. - There is the possibility of severe thunderstorms tonight with heavy rain over the NW half of the forecast area.

- Flood watch for flash flooding in effect tonight for Petroleum and southern Phillips Counties.

DISCUSSION

WEATHER PATTERN OVERVIEW: Closed upper high will linger over the northern high plains through Wednesday, keeping the heat going over the Dakotas and into our SE zones through Wednesday. Will maintain Extreme Heat Warnings for Dawson, Richland, Prairie and Wibaux Counties where heat indices up to 110 is possible today and Heat Advisories for the most of NE Montana except for Daniels and Sheridan Counties today. Then an upper disturbance sends storms northeast into the CWA this evening. Updraft helicity and Max Updraft from the HREF is showing severe thunderstorm potential for the western zones. With the high Precip Waters (1.0 to 1.8"), flooding could also be a concern. Will maintain the Flash Flood Watch for the Petroleum and Phillips Counties for tonight.

East to NE winds will be strong enough today and tonight for a Lake Wind Advisory over Fort Peck Lake.

Wednesday and beyond: Upper low over the Pacific NW then moves NE into the Prairie Provinces of Canada while the upper ridge rebounds over eastern Montana. This should keep temps warmer than normal with small chances for showers and storms.

FORECAST CONFIDENCE & DEVIATIONS:

There is high confidence in the heat continuing especially in the SE today and Wednesday. High confidence in thunderstorm chances in the NW tonight but low confidence in timing and lower confidence for thunderstorm chances for Wednesday and beyond.

Tweaked pops at times tonight and Wednesday to provide better hour to hour consistency. Otherwise, did not deviate from NBM.

AVIATION

UPDATED: 0845Z

FLIGHT CATEGORY: VFR most of the time. KGGW may have periods of MVFR conditions at times tonight.

DISCUSSION: Mainly dry weather and mostly clear skies are expected today. There will be increasing mid level clouds this evening. KGGW will have showers and thunderstorms at times after 02z with periods of MVFR conditions possible. SFC WIND: NE wind 5 to 15 knots early becoming east 15 to 20 knots with higher gusts this morning and continuing from the east this afternoon and backing to the NE tonight.

GGW WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 2 AM MDT Wednesday for Central and Southeast Phillips-Central and Southern Valley-Eastern Roosevelt-Garfield- McCone-Northern Phillips-Northern Valley-Petroleum-Southwest Phillips-Western Roosevelt.

Lake Wind Advisory from 10 AM this morning to noon MDT Wednesday for Central and Southeast Phillips-Central and Southern Valley- Garfield-McCone-Petroleum.

Flood Watch from this evening through late tonight for Central and Southeast Phillips-Petroleum-Southwest Phillips.

Extreme Heat Warning until 2 AM MDT Thursday for Dawson-Prairie- Richland-Wibaux.