textproduct: Glasgow

KEY MESSAGES

- An intense and potentially dangerous heat wave will impact northeast Montana this weekend, where daily highs will be in the 90s and 100s and lows only get down to the upper 60s to low 70s.

- There will be a risk for critical fire weather conditions for southern areas on Sunday during the peak of the heat as winds and humidity will both be in the teens. - Temperatures will moderate early next week, but are expected to remain above average.

DISCUSSION

WEATHER PATTERN OVERVIEW:

Isolated and scattered showers and thunderstorms have moved into a more favorable environment this evening for maintenance, and should continue to drift to the east for the next several hours. Eventually the lack of heating and the establishment of a stable layer should kill off what storms are currently out there.

A large upper ridge will become strongly established over the western U.S. this weekend. This is the typical pattern for giving northeast Montana very hot temperatures with clear skies. An Extreme Heat Watch is in place for Saturday and Sunday. Afternoon highs each day will be in the 90s and 100s, and some ensemble members are hinting at near 110 degrees possible in the Yellowstone River Valley on Sunday. Combine this with poor recovery (lows in the 60s and 70s each night) and higher than normal humidity (dew points in the 50s to near 70 degrees) for much of the region, and this creates a potentially dangerous heat situation for all groups of people.

While conditions will moderate some and precipitation chances will return next week, overall temps will remain near to above normal for this time of year, and heat stresses could last well into next week, especially for sensitive groups. FORECAST CONFIDENCE & DEVIATIONS:

No changes were made to the forecast from base this evening. Confidence continues to increase with respect to this weekend bringing dangerous heat to northeast Montana. Beyond this weekend, confidence lowers but is still moderate in continued warm conditions with a return of precipitation.

Cliff

AVIATION

UPDATED: Thursday July 9 at 0530Z

FLIGHT CATEGORY: VFR

DISCUSSION: Isolated to scattered showers and thunderstorms continue to drift across northeast Montana this overnight. Of the main TAF sites, it is most likely for GGW and OLF to be impacted by these storms overnight. Conditions clear for the rest of Thursday once the storms die off.

WIND: While overnight winds should remain light and variable for most areas, any airfields in the vicinity of the showers and storms could see erratic and gusty winds. Otherwise, winds will stabilize more out of the west from 5-15 kts for most of Thursday.

Cliff

FIRE WEATHER

Confidence in any critical fire weather conditions at this point is relatively low, but there is some indication that, as long as the forecast remains as it is now, that Sunday could be an elevated to near critical fire weather day, mainly for Fire Weather Zone 137 in the southwest and the southern portions of Fire Weather Zone 122. Should all the necessary conditions come together, the critical potential would be due to the extreme heat (temperatures in the 100s), low humidity (10-15% in the afternoon), and winds that are likely going to be between 10-20 mph out of the southeast.

GGW WATCHES/WARNINGS/ADVISORIES

Extreme Heat Watch from Saturday morning through late Sunday night 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.