Winter Storm Warning 1, NWS Spokane, WA

Area Forecast Discussion
National Weather Service Spokane WA
953 AM PST Sun Jan 7 2024

.SYNOPSIS...
A weather system will continue to bring light to moderate
precipitation in Eastern Washington and North Idaho through
Sunday morning. Heavy mountain snow, strong winds and a cooling
trend are likely next week along with additional chances for
light lowland snow.

&&

.DISCUSSION...
...Heavy Cascade Snow, Locally Windy, and Trending Much Colder
Next Week...

Today: We're still faced with light snow showers rotating through
northeast Washington, north Idaho and through the Palouse early this
morning. The convergence zone continues to bring snow to the Cascade
mountain passes as well. The winter weather advisories for eastern
WA/north ID will end this morning, though snow showers and light
accumulations will persist for a few more hours in the Cascades this
morning. The backside of this weather feature will rotate eastward
today with a brief break in the winter weather heading into Monday.
Clearing skies today behind the weather system will keep
temperatures cold and surfaces slick.

Monday and Tuesday: The next weather system is dropping south from
the Gulf of Alaska and we're keeping the airmass primed with cold
air aloft ready for the plume of moisture to rotate into the
PacNW. The trough will dig into the WA/OR coast late Monday and
push eastward. A westerly/zonal flow into the coast and Cascades
will produce a prolonged period of precipitation aimed at the
Cascade mountains and eastern Washington through northern Idaho.
Outside of the southern Columbia Basin (Othello to about
Sunnyside) most areas will see widespread snow accumulations
through late Monday. Monday morning parts of Eastern WA including
the metro areas of Pullman & the Palouse, Spokane/Coeur d'Alene,
northern valleys of Pend Oreille and Bonner/Boundary counties will
pick up several inches which could slow down the morning commute.
Temperatures will remain relatively cool through the day Monday
into Monday night.

Tuesday is when a proverbial wrench is tossed into the forecast
mix. The trough takes a southwest track and brings warm advection
into eastern WA along with a substantial pressure gradient of
southwest winds. 850mb wind anomalies continue to increase with
40-50+ knots punching into NE Washington. These winds (25-30 mph
and gusts 40-55 mph) will accompany the warm nose and subsequently
work to erode away some of the snow while transitioning the
precipitation type from snow to rain for most lower elevations.
Snow levels will climb to above 3000 feet through the day Tuesday.
Snowfall amounts in the Cascades and Idaho Panhandle mountains
will favor this moist, unstable, westerly flow aloft. There still
remains a 60-70% chance for 1 inch/hour rates for upwards of 18
hours Tuesday with close to 3 feet of snow forecast for Stevens
Pass. Lookout and 4th of July Pass in Idaho will see 30% chance
for 1/2 inch/hour rates.

As the precipitation shuts down later in the day Tuesday the cold
air will filter back in and temperatures will take a very sharp
turn to the cold side. /Dewey

Wednesday through Saturday: "Cold" will be the most accurate
descriptor of this part of the forecast period. The early-week
system will begin wrapping up WednesdayCoeur d'Alene morning, and
its associated gusty winds will lessen into Wednesday afternoon.

For the remainder of the week, a frigid arctic airmass will filter
southward causing temperatures to plummet regionwide. The coldest
temperatures are expected Friday through the weekend. Eastern WA and
the ID Panhandle have a 60-80% chance of experiencing much below
normal temperatures from January 12th-15th. For reference, normal
temperatures for this time of year range throughout the 30s for
highs and the 20s for lows.

While confidence is high that it will get cold, there is a lot of
uncertainty about just how cold it will get. "Warmer" models are
predicting highs in the teens and lows in the single digits, while
colder models show highs struggling to get above zero and lows well
into the negatives.

Intermittent flurries will continue through the end of the week, but
accumulations are looking minimal at this point. /Fewkes

&&

.AVIATION...
18Z TAFS: An upper trough shifting over east WA/N ID will allow
for some spotty flurries or a brief snow shower through early
afternoon, then a ridge builds in before the next system
approaches. GEG/SFF/COE/PUW will see VFR/MVFR conditions, with
VFR elsewhere. Low clouds will start to expand over the east third
of WA and ID later tonight into Monday morning, with MVFR/lcl
IFR conditions. The next system approaching from the west will
bring some risk for -sn around TAF sites after 14-15Z Monday, but
the better risk holds on until Monday afternoon.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Confidence in the
ceilings for Spokane, Coeur d'Alene and Pullman is moderate to low.
A deepening inversion overnight into early Monday will bring a
moderate to high risk for stratus expanding around Spokane, Coeur
d'Alene, Pullman toward 12-15Z. In terms of the next snow moving
into Monday, confidence is low to just bordering moderate for
development before 18Z Monday.

------------------

Confidence descriptors:
Low - Less than a 30 percent chance
Moderate - 30 to 70 percent chance
High - Greater than a 70 percent chance

For additional probabilistic information for NWS Spokane airports,
please refer to the Aviation Dashboard on our webpage:
https://www.weather.gov/otx/avndashboard

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        33  21  32  29  40  29 /  30  10  70 100 100  50
Coeur d'Alene  31  18  31  29  39  28 /  60  20  70 100 100  70
Pullman        32  22  32  29  41  29 /  40  10  50 100 100  70
Lewiston       39  27  38  35  51  34 /  20  20  30  80 100  50
Colville       33  15  27  23  38  21 /  20   0  70 100 100  50
Sandpoint      33  19  29  27  35  27 /  80  30  80 100 100  90
Kellogg        31  21  31  29  38  29 /  70  50  80 100 100  90
Moses Lake     39  24  33  30  45  31 /   0   0  70  80  50  10
Wenatchee      38  26  32  30  40  31 /   0  10  70  90  70  40
Omak           33  20  32  29  42  24 /   0   0  50  90  80  30

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Storm Watch from Monday morning through Wednesday morning
     for Central Panhandle Mountains-Coeur d'Alene Area-Idaho
     Palouse-Northern Panhandle.

WA...Winter Storm Watch from Monday morning through Wednesday morning
     for Northeast Mountains-Okanogan Highlands-Spokane Area.

     Winter Storm Watch from late tonight through Wednesday morning
     for Central Chelan County-Western Chelan County-Western
     Okanogan County.

&&

Preliminary Local Storm Report
National Weather Service Spokane WA
143 PM PST Sun Jan 7 2024

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

0830 AM     Snow             13 NNW Coolin           48.65N 116.94W
01/07/2024  E9.0 inch        Bonner             ID   Public

0900 AM     Snow             1 NE Twin Lakes         47.87N 116.85W
01/07/2024  E9.0 inch        Kootenai           ID   Public

1015 AM     Snow             3 WNW Newman Lake       47.79N 117.16W
01/07/2024  M8.0 inch        Spokane            WA   Trained Spotter

0600 PM     Snow             Spirit Lake             47.97N 116.87W
01/06/2024  M7.0 inch        Kootenai           ID   Public

0800 PM     Snow             5 W Elmira              48.49N 116.58W
01/06/2024  M6.5 inch        Bonner             ID   Public

&&