textproduct: Great Falls

KEY MESSAGES

- Daily chances for showers and thunderstorms through the weekend, with the potential for some minor mountain snow on Sunday.

- Breezy and gusty winds on Sunday, especially along the Rocky Mountain Front.

- Well below normal temperatures by Sunday.

DISCUSSION

/Issued 1218 AM MDT Fri Aug 28 2026/

Closed upper level low over Gulf of Alaska and associated upper level trough over the Eastern Pacific will dig south to over the Pacific Northwest by Saturday morning before lifting and pivoting east northeast over the Northern Rockies through the day on Sunday. Southwesterly flow aloft ahead of the approaching upper level trough will continue to transport Pacific moisture north and east over the Northern Rockies through the timeframe, which combined with surface heating during the daylight hours and subtle waves lifting northeast within the overall flow will support showers and thunderstorms across portions of Southwest through North Central Montana. While an isolated strong thunderstorm can't be ruled out through Sunday, especially on today and Saturday, most thunderstorms will be of the garden variety and produce gusty and erratic winds. High temperatures in the upper 70s to upper 80s today will fall to the 60s to low 70s by Sunday as the upper level trough moves overhead, with increasing west winds during the day on Sunday.

An active pattern looks to stay in place across the Western CONUS beyond Sunday as longwave troughing looks to remain over the Eastern Pacific, with southwesterly flow over the Northern Rockies helping to maintain near to below normal temperatures and daily chances for showers and storms. - Moldan

- Forecast Confidence & Scenarios:

Strong and Gusty Winds on Sunday...

Climate anomaly indicators are suggesting an unusual, with respect to late August wind climatology, wind event along the Rocky Mountain Front as cross barrier flow increases in wake of a departing upper level wave. H700 flow per NAEFS analysis is prog'd to increase to between 40-50kts along the Rocky Mountain Front during the day on Sunday, which is 1 to nearly 2 standard deviations above normal for this timeframe. These values combined with deep mixing during the afternoon hours on Sunday in wake of the departing upper level wave will help to support breezy and gusty winds for most locations across the plains of Central and North Central Montana, most notably along and west of the I-15 corridor where NBM5.0 probabilities currently support a 90% or greater chance for wind gusts to exceed 35 mph, with the exception of the Southern High Plains zone where probabilities generally range from a 60-75% chance. The table below lists the NBM5.0 probabilities for wind gusts to exceed 45, 55 and 65 mph during the day on Sunday.

Sunday's Wind Gusts Probabilities LOCATION > 45 mph | > 55 mph | > 65 mph Babb 60% | 20% | 5% East Glacier 70% | 20% | 5% Browning 70% | 15% | 0% Cut Bank 70% | 20% | <5% Shelby 30% | <5% | 0% Heart Butte 75% | 25% | 5% Choteau 10% | <5% | 0% Augusta 20% | <5% | 0%

Light Mountain Snowfall on Sunday...

Snow levels are expected to fall to as low as 7500ft during the day on Sunday across the East Glacier Park Region as the closed low associated with the upper level trough pivots overhead. These lowered snow level would result in some mountain passes in the backcountry of Glacier National Park potentially seeing some minor snowfall, with the latest NBM5.0 probabilities indicating a 10-20% chance for snowfall accumulations to exceed 0.1" during the day on Sunday. What remains uncertain with respect to Sunday is how much precipitation will be left over across the Northern Rockies as snow levels fall to their minimums for the day; with latest guidance suggesting that most if not all of the precipitation will fall prior to snow levels "bottoming out", which would result in little to no snowfall overall. - Moldan

AVIATION

28/12Z TAF Period

VFR/low-VFR conditions will largely prevail throughout the 2812/2912 TAF period; however, brief periods of MVFR conditions can not be ruled at the KBZN, KEKS, KWYS, and KLWT terminals through 21z this afternoon as showers and isolated thunderstorms move north and east across Southwest and portions of Central Montana. Main impact from these showers and storms will be mountain obscuration, especially for peaks at and above 9kft.

For KGTF: Southwest winds throughout the TAF period will yield nearly a non-zero chance for crosswinds to exceed 15kts; however, shower and thunderstorm activity moving south and east of the terminal beyond 18z this afternoon could produce gusty outflow boundaries that could move north and west across the terminal. The greatest areal coverage (within 50nm of the terminal) of these showers and storms looks to occur between 18z-22z this afternoon, but isolated coverage will linger into the evening and overnight hours tonight. - Moldan

FIRE WEATHER

Elevated fire weather conditions will exist across portions of Fire Weather Zone 112 today as southwest winds peak between 15-20 mph during the afternoon and evening hours, with gusts near 30 mph. The breezy winds combined with minimum relative humidly values of 15-20% west of the I-15 corridor raises concerns for the potential of new fires to spread rapidly; however, with less than half of the fire weather zone expected to see wind gusts near 30 mph we will continue to hold off on any fire weather products. - Moldan

PRELIMINARY POINT TEMPS/POPS

GTF 85 57 77 49 / 20 20 60 80 CTB 81 50 73 46 / 0 10 40 40 HLN 82 54 76 50 / 30 20 70 90 BZN 78 51 75 46 / 30 50 60 90 WYS 67 41 65 36 / 90 80 90 90 DLN 77 50 75 43 / 30 50 70 80 HVR 89 56 83 50 / 0 20 30 60 LWT 82 54 76 47 / 20 20 50 70

TFX WATCHES/WARNINGS/ADVISORIES

None.