Winter Weather Advisory 21, NWS Missoula, MT

Area Forecast Discussion...UPDATED
National Weather Service Missoula MT
510 AM MST Tue Feb 21 2023

.DISCUSSION...A mix of rain and snow has been falling across the
Northern Rockies all night, and is now taking the form of banded
precipitation in the early morning hours (at the time this
discussion was written.) So far, temperatures remain warm enough
that most valleys are still accumulating rainfall, but that will
change rather rapidly throughout the day as the Arctic front, now
crossing the Montana/Alberta border and butting up against the
Continental Divide, makes its way first into Northwest Montana
later this morning/early afternoon. It will then shift southward
and into west central Montana, north central Idaho, and southwest
Montana throughout the day and into tonight. Precipitation will
swiftly turn to snow and blowing snow, in addition to creating a
flash-freeze scenario on surfaces, as the front continues marching
through the region. The ongoing Winter Storm Warnings, Watches,
and Advisories remain in effect to account for this flash freeze
risk and the high impact it will have on the general public. In
addition, heavy mountain snow will combine with rapidly dropping
temperatures and strong winds to create dangerous backcountry
conditions and difficult travel over area mountain passes through
the day and into Wednesday.

Once the Arctic front has pushed through most of the region,
precipitation will mostly end and bitterly cold temperatures and
dangerous wind chills down to as low as -30F for valleys will
linger both Wednesday and Thursday. Bitterly cold ambient
temperatures are expected for both valleys and mountains over the
next several days. Some lingering precipitation will be possible
along the spine of the Divide and across portions of central Idaho,
however the easterly to northeasterly gradient and the deep cold
dome of air will keep conditions feeling very wintry through the
end of the week. Temperatures will begin to moderate Saturday and
Sunday across the entire region.

&&

.AVIATION...Gusty winds out of the southwest will rapidly change
to north-northeasterly throughout the day as an Arctic front
pushes over the Continental Divide and impacts most aviation
terminals today. Low level wind shear will be a concern during
this time, particularly this morning, as the atmosphere undergoes
this change. Banded precipitation currently showing up on the
radar have begun to trek from north to south early this morning
and will continue to do so throughout the morning. Temperatures
will be warm enough to support rainfall at most terminals until
the Arctic front arrives, first at KGPI with a burst of snow and
gusty winds, and then into west central Montana and southwest
Montana/central Idaho through the day.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning until 5 AM MST Wednesday for
     Kootenai/Cabinet Region.

     Winter Storm Warning until 5 AM MST Wednesday for West Glacier
     Region.

     Winter Storm Warning until 5 AM MST Wednesday for
     Flathead/Mission Valleys.

     Winter Storm Warning until 5 AM MST Wednesday for Lower Clark
     Fork Region.

     Winter Weather Advisory until 11 AM MST this morning for
     Missoula/Bitterroot Valleys.

     Winter Storm Watch from 5 PM MST this afternoon through late
     tonight for Missoula/Bitterroot Valleys.

     Winter Storm Warning until 5 AM MST Wednesday for
     Bitterroot/Sapphire Mountains.

     Winter Weather Advisory until 11 AM MST this morning for
     Butte/Blackfoot Region.

     Winter Storm Warning from 11 AM this morning to 5 AM MST
     Wednesday for Butte/Blackfoot Region.

     Winter Weather Advisory until 11 AM MST this morning for
     Potomac/Seeley Lake Region.

     Winter Storm Warning from 11 AM this morning to 5 AM MST
     Wednesday for Potomac/Seeley Lake Region.

ID...Winter Storm Warning until 4 AM PST Wednesday for Northern
     Clearwater Mountains.

     Winter Storm Warning until 4 AM PST Wednesday for Southern
     Clearwater Mountains.

     Wind Advisory until 10 AM PST this morning for
     Orofino/Grangeville Region.

     Winter Weather Advisory until 5 PM MST this afternoon for
     Eastern Lemhi County...Western Lemhi County.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
1059 AM MST TUE FEB 21 2023

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

1030 AM     HEAVY SNOW       4 SSE CRESTON           48.14N 114.10W
02/21/2023  M2.0 INCH        FLATHEAD           MT   TRAINED SPOTTER

            OCCURRED IN 1 HOUR. VISIBILITY 100 FEET.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
1234 PM MST TUE FEB 21 2023

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

1233 PM     HEAVY SNOW       4 SSE CRESTON           48.14N 114.10W
02/21/2023  M7.0 INCH        FLATHEAD           MT   TRAINED SPOTTER

            FELL SINCE 8AM, 4.5 HOURS.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
136 PM MST TUE FEB 21 2023

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

1040 AM     NON-TSTM WND DMG 7 S WOODS BAY           47.91N 114.03W
02/21/2023                   LAKE               MT   UTILITY COMPANY

            POWER OUTAGE DUE TO A TREE IN A LINE. AT THE
            TIME, YELLOW BAY POINT SHOWED NORTHEAST
            WINDS OVER 30 MPH AND IT WAS SNOWING 2 INCH
            PER HOUR RATES.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
138 PM MST TUE FEB 21 2023

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

1146 AM     NON-TSTM WND DMG 5 W WHITEFISH           48.42N 114.44W
02/21/2023                   FLATHEAD           MT   UTILITY COMPANY

            POWER OUTAGES.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
139 PM MST TUE FEB 21 2023

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

1155 AM     NON-TSTM WND DMG 3 ENE CRESTON           48.21N 114.08W
02/21/2023                   FLATHEAD           MT   UTILITY COMPANY

            POWER OUTAGES DUE TO A TREE IN A LINE.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
144 PM MST TUE FEB 21 2023

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

0100 PM     BLIZZARD         2 NNW LA SALLE          48.34N 114.26W
02/21/2023                   FLATHEAD           MT   BROADCAST MEDIA

            HODGSON ROAD BETWEEN TRUMBLE CREEK ROAD AND
            WHITEFISH RIVER WAS CLOSED DUE TO WHITEOUT
            CONDITIONS. A RECENT MEDIA PHOTO SHOWED THAT
            THE WHITEOUT CONDITIONS HAVE CEASED, BUT IT
            APPEARS THERE IS SEVERE DRIFTING.

&&