Alert archive / Montana / Winter Weather Advisories in 2021

Winter Weather Advisory 59, NWS Missoula, MT

December 7, 20214 counties in Montana

NWS Missoula, MT issued this winter weather advisory at Dec 7, 2021, 6:21 AM MST for 4 counties in Montana. It was in force for 4 hr.

The area

The counties it named.

The facts

Issued: Dec 7, 2021, 6:21 AM MST (13:21 UTC)
Expired: Dec 7, 2021, 10:05 AM MST
In force: 4 hr
Issued by: NWS Missoula, MT

Counties Flathead County, MT, Lake County, MT, Lincoln County, MT, Sanders County, MT

The radar

The Missoula radar (KMSX), 122 km from the middle of the area, began a volume at 13:24 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What forecasters said that day

The local office's own words before this winter weather advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Missoula, MT wrote its last area forecast discussion before this winter weather advisory went out at Dec 7, 3:38 AM MST, 2 hours 43 minutes earlier.

Area forecast discussion, Dec 7, 3:38 AM MST, 2 hours 43 minutes before

Area Forecast Discussion
National Weather Service Missoula MT
338 AM MST Tue Dec 7 2021

.DISCUSSION...Northwest flow aloft with a weak upper level jet
stream moving through the region will continue to produce very
light snowfall through at least this morning. Additional snow
accumulations will be light (generally an inch or less) but slick
conditions will continue through the morning commute. Temperatures
for most valley locations are expected to warm above freezing
today. The one exception is across valleys of northwest Montana,
where more stubborn inversions will be slower to dissipate.

The next weather system will approach tonight, focusing
precipitation initially through northwest Montana and the Idaho
panhandle (I90 corridor and northward). With stubborn valley
inversions likely still in place in these areas, a wintry mix of
precipitation is expected. Forecast models continue to indicate
the potential for light freezing rain, which could make for
particularly slick conditions during the Wednesday morning
commute.

Warmer air is expected to raise snow levels through the day on
Wednesday as high as 4500 feet ahead of an approaching cold front.
Forecast models continue to indicate a tightening pressure
gradient, and with the atmosphere destabilizing, breezy winds are
anticipated, especially in the higher terrain. The cold front will
surge through central Idaho and western Montana Wednesday evening,
quickly lowering snow levels back to valley floors. Mountain
passes will likely be snow covered through this time period, with
some valleys also receiving some snow again by Thursday morning.

Colder conditions will settle over the region for Thursday into
Friday, with lingering precipitation in the terrain. The next
weather system arrives Saturday into Sunday. This weather system
has a tap into subtropical moisture and will likely lead to some
significant snowfall for the mountains across northwest/west
central Montana and north central Idaho. Valleys will also receive
snowfall, though how much is still in question. This certainly
could shape up to produce a decent valley snowfall, especially
across northwest Montana.

&&

.AVIATION...Light snow will continue this morning through the
terrain of central Idaho, and much of west- central Montana,
including at KMSO. Locally lowered visibility and terrain
obscurations will be the main concerns with snowfall.
Precipitation should become more focused on the terrain by mid
day.The next shortwave is set to arrive tonight into Wednesday
with more widespread mixed precipitation once again. Locations
across northwest Montana (including KGPI) could see a period of
freezing rain around 08/0900z, continuing into mid morning
Wednesday.

&&

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

     Winter Weather Advisory until 9 AM MST this morning Lower Clark
     Fork Region.

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

     Winter Weather Advisory until 9 AM MST this morning
     Potomac/Seeley Lake Region.

     Winter Weather Advisory until 9 AM MST this morning
     Butte/Blackfoot Region.

ID...Winter Weather Advisory until 8 AM PST this morning Northern
     Clearwater Mountains.

     Winter Weather Advisory until 8 AM PST this morning Southern
     Clearwater Mountains.

&&

In the hours before

Local storm report, Dec 7, 1:23 AM MST, 4 hours 58 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
123 AM MST TUE DEC 7 2021

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

1155 PM     SNOW             6 NW MISSOULA           46.92N 114.09W
12/06/2021  M2.2 INCH        MISSOULA           MT   CO-OP OBSERVER

            CO-OP OBSERVER STATION MSOM8 MISSOULA 6 NW
            WFO.

&&

Local storm report, Dec 7, 6:07 AM MST, 14 minutes before

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The office that day

Everything else NWS Missoula, MT issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Dec 7, 2:56 PM MST	Winter Weather Advisory	MSO	Flathead, Lake, Lincoln, Mineral, Missoula, Sanders	20 hr

Nearby

Winter Weather Advisories in Montana, 2021 Every winter weather advisory in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; radar from the NEXRAD Level II archive.