textproduct: Great Falls

KEY MESSAGES

- Windy conditions tomorrow along the northern Rocky Mountain Front, with gusts up to 85 mph possible.

- Slightly cooler temperatures on Sunday, followed by seasonably average temperatures through the middle of next week.

- Cooler temperatures and increased chances of precipitation late next week into next weekend.

UPDATE

Updated forecast is out. The only change this evening was to add Eastern Toole County and Liberty County to the high wind warning. Strong winds look like they should mix down in this area, especially near the Sweet Grass Hills. Otherwise the current forecast is on track. Main concern will be the strong winds on Saturday, with the strongest winds likely occurring Saturday afternoon. Brusda

DISCUSSION

/Issued 200 PM MDT Fri Oct 16 2026/

- Meteorological Overview:

Upper level ridging continues over the region today, bringing mostly sunny skies, dry conditions and above average temperatures. As this afternoon progresses, the ridge will begin to flatten, increasing the pressure gradient and creating windy conditions, mostly confined to the Rocky Mountain Front. The ridge continues to flatten into Saturday, causing the pressure gradient to tighten even more as convergence aloft increases. This will bring strong upper level winds that, combined with diurnal heating and terrain influences, will mix down to the surface along the northern Rocky Mountain Front. This will bring very windy conditions to the northern Rocky Mountain Front, specifically in the area north of Highway 200 and west of I-15. The gusty winds are expected to dissipate by late Saturday evening as the strongest upper level winds move east and diurnal heating subsides.

Zonal flow aloft will build again on Sunday, allowing for slightly cooler temperatures and continuing the stretch of dry weather. By Monday morning, weak ridging takes its place as an upper level trough begins to move down the Pacific Coast towards northern California. This will create southwesterly flow aloft by Monday evening, which will last through the middle of next week, allowing for seasonably average temperatures.

By Thursday, the trough will have moved south of the Great Basin, creating a more direct southerly flow aloft, before moving northeast towards Wyoming. This will allow temperatures to warm on Thursday before cooling down on Friday. Increased moisture aloft will get carried north by the upper level southerly flow, increasing precipitation chances towards the end of next week into next weekend. There remains shearing and splitting in the trough late Thursday into next weekend, so while one can expect cooling temperatures and increased precipitation chances late in the forecast period, confidence in the forecast specifics for this time remains low.

- Forecast Confidence & Scenarios:

Confidence has increased on stronger winds impacting the northern Rocky Mountain Front Saturday. Models are in good agreement on an increase in the 700 mb winds, now showing around 75-80 kts, and vertical cross sections show these strong winds mixing down to the surface from late Saturday morning to late Saturday night due to diurnal heating and turbulent mixing from the terrain of the Rocky Mountains. As a result, there is also more model agreement on the wind gusts at the surface, with the spread of 10th percentile and 90th percentile wind gusts only being about a 10 mph difference. Due to the stronger 700 mb winds and increased confidence in their timing and location, the High Wind Watch (along the northern Rocky Mountain Front) has now been upgraded to a High Wind Warning, with gusts up to 85 mph possible.

Confidence was lower on these stronger 700 mb winds mixing to the surface along the rest of the Hi-Line. Soundings showed a low level inversion across the Hi-Line, which would inhibit mixing. This is supported by the vertical cross sections showing the stronger winds aloft not mixing down to the surface. While windy conditions will still be present across the Hi-Line tomorrow, the lower confidence in the strongest winds being mixed down to the surface resulted in the High Wind Watch not being extended across the Hi-Line. -Dzomba

AVIATION

17/00Z TAF Period

VRF Conditions will prevail through the TAF period. Gusty winds will continue across Central and North Central Montana through the night, tapering slightly, before increasing again on the day Saturday. High winds are expected across the Hi-Line tomorrow, with KCTB being of greatest concern with gusts 45-50kts likely, with the potential for gusts to exceed 55kts. Terminals KHVR and KGTF will also experience gusty winds with gusts 30-40kts, mixing will limit higher end gusts but there is a low (20%) chance of gusts over 50kt at both terminals. Mountain wave turbulence will also be of concern across the divide as wind pick up Saturday evening. Winds will persist beyond the end of the TAF period. -JR

PRELIMINARY POINT TEMPS/POPS

GTF 46 71 42 61 / 0 0 0 0 CTB 44 68 35 57 / 0 0 0 0 HLN 33 71 35 62 / 0 0 0 0 BZN 32 65 33 59 / 0 0 0 0 WYS 21 56 22 58 / 0 0 0 0 DLN 32 64 33 60 / 0 0 0 0 HVR 41 76 37 62 / 0 0 0 0 LWT 45 72 39 60 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

High Wind Warning from 9 AM Saturday to midnight MDT Saturday night for East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera-Eastern Toole and Liberty-Northern High Plains-Southern High Plains-Southern Rocky Mountain Front.