Forecast By SnowBrains Meteorologist – Eric McNamee
1:25 PM MST, 5/19/2021
A strong upper-level low will move into the state tonight and bring 1-3 FEET of snow to the mountains of Western Montana through Sunday.
Precipitation will begin later tonight as moisture moves in from the Pacific and interacts with the terrain.
Precipitation will continue on and off into the weekend as the center of the low moves further inland.
Snow will be heavy due to it being late in the season.
This could possibly result in some power outages across the region.
By Sunday, conditions will generally dry out as the trough moves east out of the state.
Looking out long-term, global ensembles are indicating below-average temperatures and slightly above-average precipitation for Montana.
A strong upper level low pressure system, currently centered around Vancouver Island, will dive southeastward through Washington today. As it does so, it will send copious amounts of Pacific Moisture towards the Great Falls CWA, resulting in rain, and valley snow, to develop from west to east across the area. With this system moving into the area, don`t expect highs to climb much past morning lows, as increasing clouds filter out most of todays sunshine. As this upper level low continues to slide southward across Washington and Oregon through the day today and overnight tonight, surface high pressure will move eastward across Central Canada, which will cause northerly wind to bring some colder air near the surface to the area. This influx of colder air near the surface will help to allow rain to change to snow across most of the area, while enhancing the overrunning flow brought on by southerly winds aloft on the east side of the upper level low. With plentiful moisture aloft, decent lift, and temperatures through the cloud layer just a few degrees below freezing, the snow that falls will likely have rather low snow to liquid ratios, making the snow quite heavy and wet. While warm ground temperatures may help to limit snowfall accumulations, trees and power lines will quickly cool to near freezing, allowing snow to quickly accumulate on them, especially given the wet nature of the snow. Power outages will be one of the main concerns, as well as hypothermia for newborn livestock and those recreating in the backcountry. -NWS Great Fallls 5/9/2021