textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Strong and gusty west winds continue through Friday, particularly across the higher elevations and along Continental Divide.

- Backdoor front brings snow, northeast winds across Glacier Park Region Friday into Saturday morning.

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

The main concern in the short term remains strong gusty westerly winds. Deep afternoon mixing will translate strong winds aloft down to the surface. Expect valley gusts generally in the 25-40 mph range, while mountain and ridgetop gusts frequently reach 50-70 mph. Aside from a couple light showers isolated to the mountains today, conditions will remain dry.

This breezy pattern simply hits "repeat" for Friday. We will continue to monitor the I-90 corridor from Garrison to Anaconda, where there is the possibility to reach gusts of 50 mph or greater Friday afternoon.

A backdoor cold front tracks across the US-Canada border and east of the Continental Divide Friday into Saturday morning. Recent guidance remains steadfast that this dense, cold air will struggle to make it westward across the Divide, to any significant extent, with about a 10% chance of arrival to the Flathead valley.

While the coldest air stays mostly banked to the east, some moisture in the prevailing flow aloft will produce light to moderate snow accumulations in the Glacier Park region and HWY 2 toward Marias Pass. While total snow accumulation looks relatively minor for such an area, persistent strong winds aloft and near the leading edge of the frontal boundary should lead to some blowing and drifting of snow causing travel hazards over Marias Pass through Saturday morning.

In the extended, ensemble guidance continues to indicate relatively weak and split upper level pattern with any storms tracking north and south of the region. Expect more days of mild temperatures and dry conditions through at least Tuesday of next week.

AVIATION

High confidence in VFR weather conditions through Friday, with strong winds and turbulence being the primary aviation hazards. Strong westerly flow will persist, with ridgetop winds sustained at 40-60 knots. Deep mixing will translate strong gusts down to the surface during the daytime with some relief from strong surface gusts overnight. Anticipate mechanical turbulence and mountain wave activity especially in the lee of local terrain. Overnight decoupling may introduce a separate threat for non- convective LLWS (speed and direction). Anticipate the boundary layer to mix out again and surface winds to realign with winds aloft as early as 27/1600z.

MSO WATCHES/WARNINGS/ADVISORIES

MT...Winter Weather Advisory from noon Friday to 2 AM MST Saturday for West Glacier Region.

ID...None.