textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Unseasonably warm today, with temperatures 10-15 degrees above normal.

- Cold front Friday afternoon brings strong west winds, choppy lakes, and elevated fire weather concerns.

- Cutoff low this weekend brings rain showers to Northwest Montana and snow to high peaks of Glacier National Park.

The Northern Rockies will be under the influence of a southwesterly flow pattern aloft today, with temperatures running 10-15 degrees above normal. An upper level ridge axis along and east of the divide will lead to dry conditions, with plenty of sunshine. Southerly winds will develop by the afternoon, as a low pressure system reaches the Oregon coastline. The strongest gusts (20-30 mph) will be felt across the higher elevations and southern Idaho County, ID.

A significant change arrives Friday as a dry cold front approaches from the west, associated with the aforementioned low pressure system. The front will bring gusty to locally strong winds across western Montana, crossing the US-93 corridor between 400-700 PM MDT. Most locations will see peak wind gusts of 30-40 mph, with localized gusts of 45 mph or greater across the Bitterroot Valley and in southwest Montana. The Bitterroot Valley in particular will experience localized wind channeling effects as stronger gusts (45+ mph) descent from narrow west-east orientated canyons towards the valley floor. These stronger gusts may lead to localized power outages Friday evening. Higher gusts of 45-60 mph will be felt across mountain ridgetops and the higher peaks Friday evening. Furthermore, choppy conditions on regional lakes and elevated fire weather conditions are expected. A brief line of high-based showers will accompany the front, along and north of the I-90 corridor, but little to any precipitation is expected.

A shortwave trough will track along the USA-Canada border Friday night into Saturday morning, focusing shower activity across northwest Montana and in Clearwater County, Idaho. Snow levels will lower to around 6,000 feet by Saturday morning. Snow showers will bring localized snow accumulations to mountain ranges in northwest Montana, and the higher terrain of Glacier National Park, including Logan Pass. This system will bring a significant weather change, increasing the risk of hypothermia from colder temperatures and snowfall following recent warm and dry conditions. Seasonably cool and breezy conditions will persist through Sunday.

AVIATION

The Northern Rockies airspace will be under the influence of a warm and dry southwesterly flow pattern today. South-southeast winds will develop by this afternoon for most terminals, with gusts of 10-15 kts from 24/2000-25/0000Z. High clouds will periodically pass through the area, with VFR conditions expected.

MSO WATCHES/WARNINGS/ADVISORIES

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