Strong south winds developed in Grangeville and vicinity as an area of low pressure moved into northwest Montana.
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The episode as NWS MSO wrote it up.
Strong south winds developed in Grangeville and vicinity as an area of low pressure moved into northwest Montana.
The local office's own words before the first event, 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 the first event at Dec 26, 1:35 PM PST, 11 hours 20 minutes earlier.
Area Forecast Discussion
National Weather Service Missoula MT
235 PM MST Mon Dec 26 2022
.DISCUSSION...A much warmer air mass is settling in across north-
central Idaho and across western Montana. For example it is
currently 52 in Grangeville, Idaho and 47 in Butte. Snow levels
have risen to above 6000-7000 feet across the region. However
some valley inversions have been stubborn to scour out as seen by
temps in the lower to mid 30s in the Bitterroot and Missoula
Valleys. This leads to a continuation of freezing rain in these
lower valleys. Areas across northwest Montana, lower valleys in
Glacier NP and along Highway 200 east of Missoula will experience
a mix of rain and freezing rain through Tuesday morning. Please
use caution when traveling these corridors as some areas may be
wet, however some areas may have small stretches of freezing rain
which can be just as dangerous, especially at night. The
Bearmouth Corridor along I-90 can be especially treacherous.
Winter weather advisories are in effect through Tuesday morning
from the I-90 corridor northward.
This warm air mass is accompanied by a very moist subtropical
connection extending into the central Pacific. There will be an
abundance of precipitation over the next 24 hours. Precipitation
will be intense at times with amounts up 1 to 2.5". As mentioned
snowfall will be limited to areas well above pass level (above
6000 feet) so snow impacts are not expected for those traveling
over mountain passes.
Strong winds will exist across the Camas Prairie, especially in
the vicinity of Grangeville this evening through Tuesday morning.
Expect winds up to 35 mph with gusts up to 55 mph from the south.
By Tuesday evening, the low pressure system sending moist Pacific
air into the region will begin to traverse the Canadian border
north of Montana. South of the low, a cold front will enter the
Northern Rockies on Wednesday morning. The front will bring some
changes and impacts with it. First, winds will increase out of the
south ahead of the front, then shift to the west behind the front.
Gusts in the higher terrain will reach 40 to 50 mph on Wednesday
morning. Second, snow levels will lower to valley floors behind
the front, resulting in a transition from rain to snow for the
morning commute. Windy conditions will create downsloping effects
for most valleys, so the lion’s share of the snow will be in the
higher terrain. Expect a trace to one inch on the valley floors
and 2 to 8 inches along mountain passes by Wednesday evening.
Third, the temperature change could result in slick driving
conditions, also for the Wednesday morning commute across the
entire northern Rockies. Precipitation takes a short break on
Thursday for most of the region except for the higher terrain
where some lingering moisture and a fast-moving shortwave will
fuel light mountain snow over the Glacier Park area and the
Clearwater and northern Bitterroot Ranges. Flow aloft turns mostly
westerly on Friday. Embedded moisture will keep snow in the
forecast on Friday, favoring the Clearwater Range.
&&
.AVIATION...Periods of mist and fog will continue to impact KGPI
and KMSO into this evening. Precipitation will increase tonight
and continue on Tuesday as an atmospheric river traverses the
Northern Rockies. Pockets of cold air will remain in some valleys
of Northwest Montana with freezing rain as a concern especially at
KGPI. Other valley locations may hover in the mid 30s for air
temperature but still see ice accumulation due to cold ground
temperatures. An increasing southerly gradient should fully mix
out valleys on Tuesday with gusts of 20-25 kts at times. Low level
wind shear will be a problem into Tuesday morning.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory until 11 AM MST Tuesday for
Flathead/Mission Valleys...Kootenai/Cabinet Region.
Winter Weather Advisory until 11 AM MST Tuesday for West Glacier
Region.
Winter Weather Advisory from 7 PM this evening to 11 AM MST
Tuesday for Potomac/Seeley Lake Region.
ID...None.
&&The national radar mosaic for the moment the first event began.
1 strong wind. Local standard time, as filed.
A CWOP station a few miles northwest of Grangeville measured a peak wind gust of 71 mph. The Grangeville Idaho County Airport recorded a wind gust of 61 mph. No significant power outages were observed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2022Every state in 2022This day in weather historyWarnings in Idaho, December 2022
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1063160.