textproduct: Great Falls

KEY MESSAGES

- Very warm afternoon temperatures likely most days this week.

- Daily chances for showers/thunderstorms. Some storms could be severe or produce heavy rainfall.

DISCUSSION

/Issued 143 PM MDT Sun Jul 12 2026/

- Meteorological Overview: The summer time upper level ridge of high pressure that has developed over the Western US, will generally reside over the Western US over the next week or so, just varying in how high of an amplitude it gets over Montana. The amplitude of the ridge will have some determination on hot it gets daily over the CWA.

For tonight, a weak upper level disturbance will move from southeast to northeast through the CWA. Because max temps this afternoon will be in the mid 90s, there is some potential some storms could produce strong wind gusts.

For Mon through next Sun...max daily afternoon temperatures will generally be above normal most days. Afternoon temperatures should not be quite as hot as this past weekend, but still very warm most days.

There will also be daily chances for showers/thunderstorms as upper level disturbances rotate around the upper level ridge. Some of the storms could be severe with isolated heavy rainfall possible from some storms as well.

- Forecast Confidence & Scenarios: With inverted V soundings this afternoon, any down drafts from thunderstorms could produce strong wind gusts. Thus a marginal for severe storms was placed for areas around Chinook and Harlem. Brusda

AVIATION

13/00Z TAF Period

The main concern this TAF period will be for scattered showers and thunderstorms this evening, mainly over the plains. A gusty wind shift to the northwest or north will continue to press into Central MT and Southwest MT through the evening. The strongest thunderstorms will be capable of strong and erratic winds gusts. Scattered showers and thunderstorms return tomorrow afternoon across SW MT and again will be capable of producing gusty and erratic winds. -AM

FIRE WEATHER

There is the potential that a few dry thunderstorms could develop over North Central MT this afternoon. Additionally, any thunderstorms that do develop could also produce strong wind gusts. The most favored area for thunderstorm development is generally along a line from Helena to Havre. Brusda

HYDROLOGY

The main thunderstorm concern for Tue through Thu will be the potential that some storms produce very heavy rainfall. Precipitable water is forecast to range from 1.50 to 2 inches. This would result in some storms producing very heavy rainfall in a short time. Thus much of the CWA is a marginal risk for flash flooding for later this week. Additionally, the heavy rainfall could cause additional impacts on burn scars, particularly the Horse Gulch burn area. Brusda

PRELIMINARY POINT TEMPS/POPS

GTF 62 95 64 90 / 20 0 30 10 CTB 62 90 63 85 / 10 0 20 20 HLN 65 96 67 91 / 20 0 30 20 BZN 60 96 61 93 / 10 0 10 10 WYS 49 95 52 92 / 0 0 0 10 DLN 57 93 59 90 / 0 10 20 20 HVR 63 96 66 92 / 20 0 20 30 LWT 59 93 59 90 / 10 0 0 10

TFX WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 9 PM MDT Monday for Bears Paw Mountains and Southern Blaine-Canyon Ferry Area-Cascade County below 5000ft- Eastern Pondera and Eastern Teton-Eastern Toole and Liberty- Fergus County below 4500ft-Gallatin Valley-Gates of the Mountains-Helena Valley-Hill County-Judith Basin County and Judith Gap-Madison River Valley-Missouri Headwaters-Northern Blaine County-Southern High Plains-Western and Central Chouteau County.