Helena, MT 59604 Weather

Key Messages

- Temperatures will be a roller coaster over the next several days with a mid-week warmup followed by another drop to near or slightly below seasonal averages for the weekend.

- Rain and Mountain snow will overspread the region Friday into Saturday bringing healthy liquid precipitation to lower elevations and accumulating snowfall above 4kft.

- Gusty winds develop across the area Friday afternoon into early Saturday morning. Highest gusts will be across Central MT and the Hi-Line.

Discussion

/Issued 1234 AM MDT Tue Oct 20 2026/

- Meteorological Overview:

Weak zonal flow aloft across North-Montana and weak southerly flow over SW Montana will keep conditions relatively quiet on Tuesday, with temperatures cooling to near-seasonal averages. Isolated, light showers remain possible near the Idaho border, but dry conditions will prevail everywhere else.

On Wednesday, an upper-level low settles along the California coast, increasing our southwesterly flow aloft over SW Montana while zonal flow persists across North-Central MT. Strengthened warm air advection with the southwesterly regime will rebound high temperatures back to well above seasonal averages. Mostly dry conditions will continue across the plains, though weak moisture advection supports a low chance for a shower or two along the ID/MT border.

An active synoptic pattern arrives late in the week, as the pacific low pressure eject inland, and begins to phase with the digging trough emerging out of Canada. A weak cold front will pass through the region Thursday night into Friday morning, helping initiate widespread precipitation that persists through early Saturday. This system will be fairly heavy in moisture with high confidence in a large area seeing over 0.5" of liquid precipitation. An axis of heavier amounts is likely across Southwest and Central Montana where areas could see over 1" of QPF. Precipitation will begin with high snow level Thursday night (Above 6kft). During the heaviest period of precip on Friday morning, diabatic and dynamic cooling will help pull levels down towards 5kft, transitioning much of the mountain ran to accumulation snow. As the primary deformation axis and moisture depart Friday night into Saturday, additional cold air advects in lowering snow levels below 4kft. However, mid-level drying will quick cut off precipitation rates, limiting low- elevation accumulation potential. Simultaneously, a tightening surface pressure gradient and increasing low-level lapse rates will help tap the stronger 700mb flow on Friday bringing gusty winds across the region.

- Forecast Confidence & Scenarios: Confidence is moderate to high regarding elevated post-frontal winds on Friday. The probability for gusts reaching or exceeding 45mph is 40-60% across the Hi-Line and central Plains, across the RMF and central Island ranges that rises up to 50-70%.

Aviation

20/12Z TAF Period

VFR conditions will prevail at all terminals during this TAF Period with light and variable winds and high-level clouds around. -IG

Preliminary Point Temps

GTF 57 36 71 44 / 0 0 0 0 CTB 56 30 66 38 / 0 0 0 0 HLN 62 34 66 40 / 0 0 0 0 BZN 63 33 65 37 / 0 0 0 0 WYS 59 27 60 28 / 10 10 10 10 DLN 63 35 64 37 / 0 0 10 0 HVR 61 32 68 37 / 0 0 0 0 LWT 58 34 70 44 / 0 0 0 0