textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Strong west winds across the higher elevations and near Continental Divide.

- Snow across Glacier Park Region Friday into Saturday.

- Mild and dry weather pattern for most places through at least the middle of next week.

A low pressure system moving east of the divide into Friday will drive a modest pressure gradient across the Northern Rockies. This pressure gradient will create gusty westerly winds, particularly across mountain areas, where peak gusts will reach 45-55 mph this afternoon. Valley areas can expect gusts of 25-40 mph, with the highest gusts in west-east orientated valleys. A similar pressure gradient pattern will continue into Friday, with peak wind gusts trending a touch higher in southwest Montana and along the divide. The I-90 corridor from Garrison to Anaconda stands out for stronger gusts, where statistic guidance has a >50% chance for peak gusts of 50 mph or greater. Subsequent shifts will monitor this trend closely for potential wind highlights.

The next weather system tracks along the US-Canada border late Friday into Saturday, with precipitation spreading across Lincoln and Flathead Counties. Model guidance has been consistent with focusing snow accumulations across the Glacier Park region, especially along US Highway 2 over Marias Pass. Confidence in snow amounts remains low, with low-end (25th percentile) and high-end (75th percentile) snow amount forecasts of 1 and 8 inches, respectively. Minor accumulations also are in play for US-93 from Eureka to Whitefish and in the Yaak region, where there's a 40-50% chance of measurable snow.

Forecast models show an arctic air mass banking along the Continental Divide Friday night into Saturday. Guidance has been consistent in recent runs with this arctic front struggling to push over the divide, with only a 10% chance of the colder air advancing into the Flathead Valley. The front will bring colder temperatures to higher elevations of Glacier Park and along US Highway 2 from Essex to Marias Pass.

Looking ahead to the middle of next week, a split flow weather pattern is highlighted by ensemble guidance with the storm track focusing well north in Canada and across the southwest US. This places the Northern Rockies under a ridge of high pressure will mild temperatures and little chance for precipitation.

AVIATION

A modest pressure gradient will drive gusty winds by this afternoon, with stronger ridgetop winds of 30-40kts leading to areas of mountain wave turbulence. Terminals can expect gusts between 15-25kts, primarily from 26/1900-27/0000Z, with stronger gusts at times along and near the Continental Divide.

MSO WATCHES/WARNINGS/ADVISORIES

MT...None. ID...None.