textproduct: Glasgow

KEY MESSAGES

- Hot temperatures continue though at least Thursday with highs in the 90s to around 100 degrees. - Gusty southeast winds starting Tuesday will lead to critical fire weather in areas of dry fuels and a hazard to small craft on Fort Peck Lake.

- Isolated thunderstorms are expected by Tuesday evening, with additional chances through the week.

DISCUSSION

WEATHER PATTERN OVERVIEW: Temperatures will continue to heat up across NE Montana heading into Tuesday thanks to an upper ridge pattern. High temperatures Tuesday will be well into the 90s to around 100 for the Missouri and Yellowstone River Valleys. Afternoon humidity as low as the 10-15% range and gusty southeast winds starting Tuesday will raise elevated to critical fire concerns dependent on fuels. At this time, most of the area has a Heat Advisory Tuesday and areas east of Hwy 24 have a Red Flag Warning due to less green up there. With similar conditions extending into at least Wednesday, there is potential for more heat or fire headlines. A high vapor pressure deficit from the hot and dry week will eventually lead to a degree of curing of fuels as well. The gusty southeast winds also present boating hazards for Fort Peck Lake and the persistent pattern will not allow them to subside much for a few days after ramping up on Tuesday. The Lake Wind Advisory has been extended through Wednesday night.

On Tuesday afternoon, an upper trough with lee cyclogenesis will move in from the west to produce thunderstorms across central Montana. These storms will make progress eastward into NE Montana by the evening. An isolated strong gust from a thunderstorm or collapsing shower is certainly possible with inverted-V soundings, though most activity will remain to be forced over higher terrain of central Montana.

Wednesday through Friday will continue to feature a deep trough across the western CONUS and a ridge to the east. NE Montana will be sandwiched in between with thunderstorm chances each day, especially in afternoon and evening hours. Some of the storms have the potential to be on the stronger side and may produce brief heavy downpours. However, the latest model trends have favored NE Montana remaining hotter/drier under the ridge side which poses more of a continued fire weather threat.

FORECAST CONFIDENCE & DEVIATIONS:

NBM was largely used for the forecast period, with slight adjustments for the wind and fire headlines with highly anomalous heat in place. Confidence is high for hot, dry, and windy conditions on Tuesday leading to heat, fire weather, and lake wind concerns, as well as convective potential later in the day. Confidence is more moderate on the synoptic scale after Wednesday, impacting thunderstorm coverage and temperatures.

AVIATION

LAST UPDATED: 0000Z.

FLIGHT CAT RANGE: VFR.

DISCUSSION: Excellent flying weather looks to continue through Tuesday afternoon with mid to high clouds moving across the terminals at times.

DENSITY ALTITUDE: will be high due to thinner air in the afternoon with temperatures up to near 100 degrees through Thursday.

WIND: Light and variable with occasional gusts to 15 kts out of the west, then establishing out of the southeast at 10 to 20 knots, gust 30 kts after 15Z Tuesday.

EQUIPMENT: KSDY obs are unavailable and will be AMD NOT SKED.

/GAH

GGW WATCHES/WARNINGS/ADVISORIES

Lake Wind Advisory from 9 AM Tuesday to 6 AM MDT Thursday for Central and Southeast Phillips-Central and Southern Valley- Garfield-McCone-Petroleum.

Heat Advisory from noon to 9 PM MDT Tuesday for Central and Southeast Phillips-Central and Southern Valley-Daniels-Dawson- Eastern Roosevelt-Garfield-McCone-Northern Phillips-Northern Valley-Petroleum-Prairie-Richland-Sheridan-Western Roosevelt- Wibaux.

Red Flag Warning from noon to 9 PM MDT Tuesday for Dawson/McCone/Prairie/Richland/Wibaux Counties-Fort Peck Reservation and Daniels/Roosevelt/Sheridan Counties.