textproduct: Great Falls

KEY MESSAGES

- Wildfire smoke will bring hazy skies or smoky conditions to the Northern Rockies, with air quality degradation through the week.

- Hot temperatures will continue through Saturday, with Saturday being the hottest day.

- Afternoon showers and thunderstorms are possible across Southwest and portions of Central Montana through Friday.

- High Winds are possible along the Rocky Mountain Front Saturday night through Sunday morning, with gusty winds expanding to all areas on Sunday.

DISCUSSION

/Issued 1222 AM MDT Thu Jul 30 2026/

Upper level ridging through the day on Saturday will help to maintain well above normal temperatures across all of the Northern Rockies, with high temperatures peaking on Saturday as increasing flow and strong warm air advection brings readings into the mid-90s to near 110 degrees. While overall dry conditions will persist beneath this ridge there remains enough monsoonal moisture spreading north and east across portions of Southwest and into Central Montana to support isolated to widely scattered showers and thunderstorms during the afternoon and evening hours through Friday. Biggest impact from the showers and thunderstorms will be gusty and erratic outflow winds. By Saturday night the upper level ridge will be broken down by a potent upper level trough sliding east across Southern Canada, with this trough and attendant (dry) cold front brining gusty winds to all areas for the day on Sunday and below temperatures for the day on Monday. - Moldan

- Forecast Confidence & Scenarios:

Return of Extreme Temperatures by Saturday...

Climate anomaly indicators remain honed in on Saturday being the hottest day of the upcoming week, with ECMWF EFI values peaking between 0.75 and 0.9 across Southwest through North Central Montana; which continues to suggest unusual to very unusual hot temperatures with respect to early August climatology. This is remarkable considering that August 1st is only one day removed from the climatological peak for average high temperatures across Southwest through North Central Montana.

The table below represents the potential high temperature scenarios for select cities across Southwest through North Central Montana, with the "Low End" scenario being the NBM10Pct (10% chance that temperatures are lower than the listed value), "Most Likely" scenario being the NBM50Pct, and the "High End" scenario being the NBM90Pct (10% chance that temperatures exceed the listed value).

Saturday's High Temperature Scenarios LOCATION Low End | Most Likely | High End Browning 88 | 93 | 95 Cut Bank 95 | 100 | 102 Havre 104 | 108 | 110 Great Falls 102 | 103 | 105 Lewistown 98 | 101 | 103 Helena 98 | 100 | 104 White Sulphur Springs 94 | 97 | 99 Bozeman 99 | 103 | 105 Dillon 94 | 97 | 98 Ennis 93 | 97 | 99 West Yellowstone 89 | 91 | 93

While wildfire smoke can significantly influence high temperatures by limit heating...the past few days have only seen minor impacts to forecasted highs. Therefore the earlier (in the week) concerns that I had on forecasted highs being held below the 50Pct, or "Most Likely" scenario, on Saturday have decreased. Given this increased confidence in hot temperatures occurring on Saturday, most notably over portions of the Central and North Central Montana plains, an Extreme Heat Watch has been issued from 18z Saturday through 18z Sunday due to the hot daytime temperatures and limited cooling (as compared to climatology) during the overnight hours.

High Winds from Saturday night through Sunday morning...

H700 winds of 40-60kts, which is an impressive 3 to nearly 4 standard deviations above normal per NAEFS analysis, are prog'd to overspread the Rocky Mountain Front from 00z Sunday through 18z Sunday. BUFKIT soundings support ideal thermal profiles, especially between 06z and 14z Sunday, for mountain wave activity across the Eastern Glacier Park Region out to Cut Bank. This anomalous cross barrier flow combined with the potential for mountain wave activity has increased concerns that High Winds could materialize across all of Glacier County and portions of western Toole and central Pondera Counties. For this reason a High Wind Watch has been issued from 03z Sunday through 18z Sunday for these areas, with the most concerning timeframe being between 06-14z Sunday. Those looking to travel or recreate along the Rocky Mountain Front should be prepared for strong winds; which could make driving and hiking difficult, lead to falling trees in the backcountry, and/or lead to the spread of existing/new wildfires.

The table below represents the potential wind gust scenarios for select locations along the Rocky Mountain Front, with the "Low End" scenario being the NBM10Pct (10% chance that gusts are lower than the listed value), "Most Likely" scenario being the NBM50Pct, and the "High End" scenario being the NBM90Pct (10% chance that gusts exceed the listed value).

Saturday Night/Sunday Wind Gust Scenarios LOCATION Low End | Most Likely | High End Many Glacier Valley 35 mph | 50 mph | 60 mph Logan Pass 35 mph | 45 mph | 55 mph St Mary 40 mph | 55 mph | 65 mph Two Medicine Valley 40 mph | 60 mph | 70 mph Marias Pass 35 mph | 40 mph | 50 mph East Glacier 45 mph | 55 mph | 65 mph Browning 40 mph | 45 mph | 60 mph Cut Bank 40 mph | 45 mph | 55 mph Heart Butte 40 mph | 50 mph | 65 mph

- Moldan

AVIATION

30/12Z TAF Period

VFR conditions will predominately prevail throughout the 3012/3112 TAF period; however, regional wildfire smoke may at times reduce VIS to low-VFR, with slantwise visibility being affected across all terminals over the next 24 hours. Otherwise scattered showers and thunderstorms will begin to develop between 18-21z this afternoon over the higher terrain of Southwest and Central Montana. These showers and thunderstorms will then lift northeast, possibly as a cluster, from the late afternoon through evening hours and potentially affect the KEKS, KBZN, KHLN, KGTF, and KLWT terminals with gusty and erratic winds.

For KGTF: Light and variable winds will veer to the southwest and west through the afternoon hours, with isolated gusts being possible due to deep, diurnal mixing from the late afternoon into the early evening hours. The probability of this west wind exceeding a 15kt crosswind is 10% between 30/23z and 31/02z. - Moldan

FIRE WEATHER

Elevated to critical fire weather conditions is expected Saturday afternoon through Sunday evening across North-Central, Central, and Southwest Montana. On Saturday, hot temperatures in the upper 90s to near 110 degrees will combine with minimum RH values as low as 8% and gusts up to 50 mph with stronger gusts expected along the Rocky Mountain Front to create the potential for critical fire weather conditions. Sunday will be cooler but low RH values and strong winds are still expected which will still pose a significant concern not only for ongoing fires but any potential new starts that occur. Given all this, a Fire Weather Watch remains in effect from Saturday afternoon through Sunday. -thor

PRELIMINARY POINT TEMPS/POPS

GTF 96 61 97 60 / 0 10 10 0 CTB 90 55 91 55 / 0 0 0 0 HLN 94 59 96 60 / 20 30 10 0 BZN 94 57 95 57 / 20 20 10 0 WYS 85 46 87 47 / 10 10 0 0 DLN 89 54 90 55 / 20 20 10 0 HVR 97 60 98 58 / 10 10 10 0 LWT 91 59 93 59 / 30 20 10 0

TFX WATCHES/WARNINGS/ADVISORIES

Extreme Heat Watch from Saturday afternoon through late Saturday night for Cascade County below 5000ft-Eastern Pondera and Eastern Teton-Judith Basin County and Judith Gap.

Fire Weather Watch from Saturday afternoon through Sunday evening for Central and Eastern Lewis and Clark National Forest Areas-Chouteau and Fergus Counties-Eastern Glacier/Toole/Central/Eastern Pondera/Liberty-Helena and Townsend Ranger Districts of the Helena National Forest-Hill and Blaine Counties-Lewis and Clark National Forest Rocky Mountain District-Rocky Mountain Front-Lincoln Ranger District of the Helena National Forest.

High Wind Watch from Saturday evening through Sunday morning for East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera-Northern High Plains.

Extreme Heat Watch from Saturday afternoon through Sunday morning for Bears Paw Mountains and Southern Blaine-Fergus County below 4500ft-Western and Central Chouteau County.