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KEY MESSAGES

- High heat is expected across northeast Montana today. Highs will be in the upper 90s to around 110. An Extreme Heat Warning is in effect through tomorrow morning. There is potential for an extension into the southeast for tomorrow afternoon.

- A Red Flag Warning is in effect for today, and a Lake Wind Advisory and High Wind Warning for tonight due to a strong surface boundary moving through the area. - Temperatures will moderate early this work week, but are expected to remain above normal. Precip chances return by Tuesday night.

DISCUSSION

WEATHER PATTERN OVERVIEW: An upper ridge is over the area, and the peak heat is expected to build in today before the ridge breaks down slightly tomorrow. The base NBM indicates lows staying above 65 degrees for this morning and Monday morning, so it will be difficult to stay cool enough to sleep comfortably. There is an extreme heat warning in place for the heat through this evening. There is potential for this warning being extended in the southeast for at least tomorrow afternoon when the next meteorologist updates the forecast this evening.

Repeated CAM runs have suggested strong downdraft CAPE (up to 2700 J/kg) and enough of a forcing this evening in the northwest to bring down some severe wind gusts. A marginal risk for dry thunderstorms has been put out by SPC for the northwest part of the area from about 4 PM this evening through 10 PM.

A strong southerly low level jet in the southeast has permitted a High Wind Warning to be put out for gusts as high as 60 mph for part of tonight, and a Lake Wind Advisory is in effect for a surface front moving through overnight. A Red Flag Warning is also in effect through this evening for low relative humidity, high heat, and gusty south winds.

Tomorrow is expected to be a bit quieter with headlines. Although the heat is expected to come down a tad, high temperatures will still be rather toasty in the upper 80s to upper 90s. This pattern will likely remain in place for the next 3 days.

A slight breakdown in the ridge is expected with a shortwave trough that is supposed to move through on Tuesday afternoon. A few wiggles in the upper level flow are expected on Wednesday and Thursday, so shower and storm chances will continue through the end of the work week most likely. The warm temperatures may inhibit widespread accumulating rain from soaking into the ground, but any precipitation is welcome.

FORECAST CONFIDENCE & DEVIATIONS: Blended HRRR and HRWFV3 for day 1 and day 2 winds. Increased PoPs to slight chance in the west for this afternoon and evening.

There is HIGH confidence on temperatures exceeding 100 degrees for high temperatures and low temperatures struggling to drop below 65 degrees for today, and low to moderate confidence of a few locations reaching 100 tomorrow.

There is low to moderate confidence in fire weather concerns for today. There is high confidence in the Lake Wind Advisory, and moderate confidence in the High Wind Warning for tonight.

There is LOW to MODERATE confidence of an isolated dry thunderstorm producing a 60 to 65 mph wind gust from 4 PM to 10 PM today in the western half of the CWA.

There is HIGH confidence of precipitation chances returning by Tuesday evening.

AVIATION

UPDATED: 1830Z

FLIGHT CATEGORY: VFR

DISCUSSION: Mainly dry weather and mostly clear skies are expected over the TAF cycle. A few model runs suggest isolated dry thunderstorms for KGGW later today.

There is low confidence (5-10%) in isolated gusts as high as 65 mph from 22Z through 04Z Monday. A gust of wind may simply come out of an otherwise innocent looking cloud with virga coming out of the bottom.

DENSITY ALTITUDE: Hot temperatures near and above 100 degrees will lead to needs for increased length of runway and increased power for take off. Worst times will be in the afternoon and evening from 18Z to 03Z today.

WIND: For KGGW and KOLF, south southeast at 10 to 20 knots with gusts to 30 knots, becoming north at 10 to 20 knots with gusts to 32 knots for KGGW and KOLF after 02Z, decreasing to 8 to 15 knots after 12Z, becoming northeast at 8 to 14 knots after 18Z Monday. For KSDY and KGDV, south at 10 to 20 knots, becoming north northeast after 14Z.

LLWS: From 04Z to 12Z, south at 40 knots becoming west northwest.

GGW WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 6 AM MDT Monday for Central and Southeast Phillips-Central and Southern Valley-Daniels-Dawson- Eastern Roosevelt-Garfield-McCone-Northern Phillips-Northern Valley-Petroleum-Prairie-Richland-Sheridan-Southwest Phillips- Western Roosevelt-Wibaux.

Red Flag Warning until 9 PM MDT this evening for Southern Petroleum and Southern Garfield Counties-The Lower Missouri River Breaks including the Charles M Russell National Wildlife Refuge.

Lake Wind Advisory from 9 PM this evening to 6 AM MDT Monday for Central and Southeast Phillips-Central and Southern Valley- Garfield-McCone-Petroleum.

High Wind Warning from 9 PM this evening to 4 AM MDT Monday for Dawson-Eastern Roosevelt-McCone-Prairie-Richland-Sheridan-Wibaux.