textproduct: Great Falls

KEY MESSAGES

-Abnormally warm, dry, and breezy conditions continue today, with stronger winds developing across Southwest Montana valleys on Friday.

-A passing system Saturday into Sunday initiates a cooling trend toward seasonal averages, with light precipitation and high- elevation snow confined largely to far Southwest Montana.

-Cooler, more unsettled conditions return next week, though high uncertainty remains in timing and storm track.

DISCUSSION

/Issued 451 PM MST Thu Nov 12 2026/

- Meteorological Overview:

Strong upper-level ridging remains in control across Montana today and Friday, keeping conditions abnormally warm and dry with general breeziness across the region today. By Friday, a potent Pacific trough begins digging inland along the West Coast, increasing southwesterly flow aloft and tightening the surface pressure gradient across Southwest Montana. This setup will favor increased winds developing south of I-90, particularly channeled within north-south oriented valleys.

On Saturday, the trough tracks eastward across the Great Basin, breaking down the ridge and shifting flow aloft to southerly. This transition initiates a cooling trend that will bring temperatures back toward seasonal averages for the remainder of the forecast period. Moisture transported northward ahead of this wave will be heavily limited to Southwest Montana and the higher terrain, keeping most lower elevations dry. With snow levels hovering around 7,000 to 8,000 ft, any wintry precipitation will be restricted to the highest mountain peaks primarily from Saturday into Sunday. The fast- moving trough exits toward the Southern Plains on Sunday, allowing weak shortwave ridging to briefly rebuild by Sunday afternoon with partly sunny, dry conditions and seasonable temperatures.

Uncertainty increases substantially starting Monday as a deep upper-level trough moves inland across Southern California and re- establishes southwesterly flow aloft. While recent guidance shows a slight uptick in moisture potentially reaching parts of the area, centered largely from Tuesday night through Wednesday night, models remain divided on how this energy evolves. Earlier signals for this system closing off into a cutoff low are becoming less likely; instead, forecast spread now centers on how far south the trough digs and whether it simply progresses eastward or takes on a negative tilt and propagates northeastward, which would pull more active weather into the region. -JR

- Forecast Confidence & Scenarios:

High confidence surrounds the unseasonable warmth through Friday and the increasing winds in Southwest Montana valleys tomorrow.

Confidence is also high that the Saturday into Sunday system will be low impact, with precipitation probabilities heavily concentrated in far Southwest Montana. Along the Montana/Idaho border, probabilities are 50-60% for exceeding 0.10 inches of liquid and 30-40% for exceeding 0.20 inches, dropping to a 20% chance for >0.10 inches south of Highway 287. High snow levels will confine accumulations to a dusting from 8,000 ft and up, with 40-60% chance of >1 restricted solely to the highest peaks of the Centennial Mountains and Blacktail Range.

Confidence drops to low-to-moderate for next week due to ongoing model spread regarding how far south the incoming trough digs, its tilt, and its subsequent track. Currently, the 48-hour probability for receiving 0.25 inches or more of liquid from Tuesday night through Wednesday night sits at a widespread 20-40%, with higher probabilities favored across Southwest Montana:

Scenario 1 (Southern Dig / Progressive Eastward Track): The incoming trough digs further south and progresses steadily eastward across the Great Basin and Central Rockies. This keeps the primary moisture plume and strongest dynamic lift displaced south of Montana, resulting in near-seasonal temperatures and periodic, light precipitation with minimal winter impacts.

Scenario 2 (Negative Tilt / Northeastward Propagation): Rather than progressing straight east, the trough acquires a negative tilt and propagates northeastward across the Northern Rockies. Capitalizing on the recent uptick in moisture guidance, this evolution would bring more widespread precipitation Tuesday night into Wednesday night. In addition to increased precip, this scenario would promote further cold air to advect behind the system bringing the potential for below seasonal norms, though confidence in this track remains lower. -JR

AVIATION

13/06Z TAF Period

Freezing fog will prevail along the Milk River Valley including KHVR through Friday morning. How fast the fog clears will be dependent on when the easterly winds start to pick up. The latest model guidance points towards 13/19Z but it could be as early as 13/17Z or as late as 13/22Z. Once the fog clears, VFR conditions will prevail through the remainder of the period.

Across all other terminals, VFR conditions will prevail through the TAF period with passing broken to overcast high-level clouds. -thor

PRELIMINARY POINT TEMPS/POPS

GTF 39 66 40 62 / 0 0 0 0 CTB 32 55 29 57 / 0 0 0 0 HLN 33 60 35 55 / 0 0 0 10 BZN 32 61 33 56 / 0 0 0 10 WYS 25 52 27 42 / 0 0 10 50 DLN 32 57 34 50 / 0 0 0 30 HVR 32 56 31 58 / 0 0 0 0 LWT 39 67 38 63 / 0 0 0 0

TFX WATCHES/WARNINGS/ADVISORIES

None.