textproduct: Great Falls

KEY MESSAGES

- Hot temperatures continue for another day before cooling off slightly during the workweek.

- Dry, breezy to windy, and hot conditions will bring elevated fire danger over southwest Montana this afternoon.

- Daily rounds of shower and thunderstorm activity returns by Monday and will be most widespread Tuesday through Thursday.

- Some storms will be on the stronger side and may contain strong, gusty winds, hail, and torrential downpours capable of localized flooding.

DISCUSSION

/Issued 1204 AM MDT Sun Jul 12 2026/

- Meteorological Overview:

Ridging aloft will maintain hot and dry conditions again today while southwesterly flow strengthens aloft. Deep layer mixing will transfer the 30 to 40 kt H700 winds to the surface especially over southwest MT where elevated fire weather conditions will be present later today. A subtle shortwave will clip the northwestern portion of the forecast area and will bring a northwesterly wind shift to most locales this afternoon and evening, although there will not be cooling relief on the backside of this feature.

The 597 dm high will move eastward towards the plains with southwesterly flow aloft becoming entrenched over the Northern Rockies by Monday. This will advect monsoon moisture in from the desert southwest and increase PWATS up the 0.90 to 1.30 inch range by Tuesday and Wednesday according to the North American Ensemble Forecast System (NAEFS). This moisture will interact with passing shortwaves and CAPE generally between 700 and 1500 J/kg for daily rounds of scattered showers and thunderstorms, with some storms containing strong, gusty winds, hail, and torrential downpours in addition to cloud to ground lightning. Temperatures will cool slightly from the weekend with the added clouds and convective activity.

A majority of ensembles highlight the the 597 dm ridge migrating back towards the Great Basin by early next week, but the Northern Rockies will remain on the periphery of this feature and still maintain an unstable west to southwesterly flow aloft for at least isolated to widely scattered shower and thunderstorm activity. - RCG

- Forecast Confidence & Scenarios:

Hot temperatures and breezy, dry conditions today...

Deep layer mixing and stronger southwesterly flow aloft will increase surface winds today while maintaining hot and dry conditions. The winds will be strongest for southwest MT areas east of I15, especially the south to north oriented valleys where isolated gusts over 50 mph will be plausible. The primary impact will be elevated fire weather conditions, see the fire weather section for more information.

As far as temperatures go, today will be the hottest day with highs generally running between 95 and 105 degrees. There will be some isolated areas along the Missouri River Breaks and in the Fort Belknap area that may see highs exceeding 105. Temperatures remain very warm heading into the workweek, although not quite as intense. No changes were made to the inherited heat advisories.

Daily rounds of showers and thunderstorms return for much of the upcoming week...

Increasing moisture and instability may bring a few isolated gusty showers and thunderstorms as early as late this afternoon and evening, especially over central and north-central MT. Otherwise, Monday through Thursday will see the most widespread showers and thunderstorms. While all these days will need to be monitored for localized strong, gusty winds, hail, and torrential downpours, Tuesday and Wednesday look to have anomalously high PWATS that may exceed 1.25 inches over central and north-central MT. These days will be highest at risk for localized flash flooding, especially flood sensitive areas like burn scars and urban areas. This has prompted the Weather Prediction Center to highlight much of the forecast area with a marginal risk (5 to 15% chance) for flash flooding for days 3 and 4. - RCG

AVIATION

12/12Z TAF Period

VFR conditions prevail through the TAF period with a gradual increase in high level clouds by this afternoon. Cumulus development this afternoon will progress to high-based showers and potentially an isolated thunderstorm or two across mainly eastern portions of north-central MT. The main risk with this is the potential for gusty and erratic downdraft winds, particularly near KLWT and KHVR. South to southwest surface winds increase at most terminals by early this afternoon with a wind shift to the northwest occurring from north to south across the area late this afternoon through this evening. Hoenisch

FIRE WEATHER

Fire weather concerns for today will continue to be most impactful across southwest MT where winds will be stronger and fuels are most receptive. Probabilities for wind gusts in excess of 40 mph increase to 60% or greater over much of southwest MT by this afternoon, especially for locations east of I15. This includes areas as far north as the valleys of Broadwater and Meagher counties. The combination of the winds with near record afternoon temperatures and critically low humidity have resulted in the Hot-Dry-Windy Index exceeding the 90th percentile over these areas this afternoon for elevated fire weather conditions. Additionally, there will be a weak boundary that brings a northwesterly wind shift during the evening hours. - RCG

PRELIMINARY POINT TEMPS/POPS

GTF 100 62 95 64 / 10 20 20 20 CTB 91 61 90 63 / 10 10 10 20 HLN 100 64 96 67 / 10 20 20 20 BZN 103 60 96 61 / 10 10 10 20 WYS 97 50 95 52 / 0 0 10 0 DLN 99 57 93 58 / 10 0 20 20 HVR 102 63 96 66 / 10 30 10 30 LWT 104 59 93 59 / 10 20 10 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.