Winter Storm and Heavy Snow in Idaho, February 11 to 13, 2019

Area Forecast Discussion
National Weather Service Missoula MT
232 PM MST Mon Feb 11 2019

...PROLONGED SNOW WITH PERIODS OF MODERATE SNOW THROUGH THE MIDDLE
OF THE WEEK...

.DISCUSSION...The brief break in snow this afternoon will be
short-lived as a warm front quickly brings a return to snow
during this evening.

A period of overrunning (warm frontal boundary moving over a cold
air mass near the surface) will produce moderate to heavy snow
tonight into Wednesday across portions of north central Idaho and
northwest Montana. Snow will initially impact north central Idaho
and western Montana tonight before spreading across northwest
Montana by early Tuesday morning. Winter Storm Warnings have been
issued for parts of north-central Idaho and northwest Montana as
intense period of snowfall is expected as the warm frontal
boundary is lifted over the cold air stuck near the surface.
Snowfall rates on the order of one to two inches per hour will be
common along this warm frontal boundary as it lifts northward into
northwest Montana Tuesday morning. 6 to 10 inches of snowfall is
anticipated across these areas, with over a foot of snow in the
higher terrain near the Idaho/Montana border. Further south and
east, across west central Montana, snowfall will generally be the
1 to 4 inch range.

A surface low will track across central Oregon into northeast
Washington tonight and will act to increase a southerly pressure
gradient across north central Idaho. This will bring an increasing
trend to winds through the Camas Prairie in Idaho and southwest
Montana through Tuesday afternoon. The wind combined with
snowfall will make for a period of lowered visibility due to
blowing snow across the Camas Prairie, particularly near the
Grangeville area.

Warm and moist air will continue to stream across much of the
Northern Rockies Wednesday. The greatest impacts will be felt
across the I-90 corridor west of Missoula through Lookout Pass and
for Highway 2 from Columbia Falls through Marias Pass. Elsewhere
a band of light to moderate snowfall will track north to south
from northwest Montana through west-central Montana and north-
central Idaho Wednesday morning through the afternoon, with
additional snowfall expected. By Wednesday evening, snowfall
across Lookout, Lolo, and Marias Passes will need to be measured
with a yardstick!

There are still questions on the evolution of the weather pattern
for Thursday and Friday. The moisture and snow focus does still
look to transition southward but may only linger for a short
period of time during Wednesday night and Thursday morning.
Another weather system is likely to arrive on Friday with higher
snow levels to start and periods of snow for the weekend.

&&

.AVIATION...Radar returns are starting to increase as a warm front
moves into the region. Snow will return during the evening with
widespread lowered ceilings, obscured terrain, and consistently
reduced visibility through the overnight and into Tuesday morning.
Moderate to heavy snow is expected in portions of north-central
Idaho and northwest Montana tonight through at least Tuesday
night. Winter Storm Warnings have been issued to account for the
heavy snow, where low elevations can expect 6 to 10 inches of snow
by Tuesday evening and around 20 inches in the mountains.
Southwesterly winds will increase in the terrain and in
Grangeville tonight.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 9 AM MST Tuesday
     Missoula/Bitterroot Valleys.

     Winter Storm Warning from 11 PM this evening to 5 PM MST
     Wednesday Lower Clark Fork Region.

     Winter Storm Warning from 2 AM to 1 PM MST Tuesday
     Flathead/Mission Valleys.

     Winter Storm Warning from 2 AM Tuesday to 5 PM MST Wednesday
     West Glacier Region.

     Winter Storm Warning from 11 PM this evening to 5 PM MST
     Wednesday Kootenai/Cabinet Region.

     Winter Weather Advisory until 9 AM MST Tuesday
     Bitterroot/Sapphire Mountains.

     Winter Storm Warning from 2 AM to 1 PM MST Tuesday
     Potomac/Seeley Lake Region.

ID...Winter Storm Warning until 10 AM PST Tuesday Orofino/Grangeville
     Region.

     Winter Storm Warning until 4 PM PST Wednesday Northern
     Clearwater Mountains...Southern Clearwater Mountains.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
755 PM MST MON FEB 11 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0754 PM     SNOW             COLUMBIA FALLS          48.37N 114.18W
02/11/2019  M3.0 INCH        FLATHEAD           MT   PUBLIC

            3 INCHES FELL OVERNIGHT SUNDAY AND MONDAY
            MORNING.

&&