Winter Weather in Washington, January 11 to 16, 2024

Area Forecast Discussion
National Weather Service Spokane WA
334 PM PST Thu Jan 11 2024

.SYNOPSIS...
Temperatures will become much colder today into early next week
with an Arctic front. This will bring the potential for snow,
blowing snow, and snow squalls the region through this evening.
Bitterly cold wind chills with northerly winds Friday through
Saturday. Drier but cold weather is expected for several days
before more snow moves in by mid-week. Meanwhile the temperatures
should moderate slowly later in the week.

&&

.DISCUSSION...

...STRONG ARCTIC COLD FRONT WILL PUSH THROUGH THE INLAND NORTHWEST
OVERNIGHT...

Tonight Through Saturday: A strong arctic front cold front
is currently dropping southward through the Okanogan Valley
and into the Columbia Basin. This air mass features low dewpoint
temperatures in the single digits and winds of 30-45 mph. The
harshest conditions are occurring in the Okanogan Valley and the
Waterville Plateau and this should continue through much of the
night. Meanwhile even colder air was being bottled up just east of
the Continental Divide and this should surge in overnight as a
surface low just south of the Silver Valley drops further south
overnight. Once that occurs...northeast winds will pour down the
Purcell Trench and then spread across the Spokane/CdA area and
eventually into the eastern Columbia Basin.

*Temperatures & Wind Chills: Temperatures and dewpoints will
 plummet accordingly with wind gusts of 20-30 mph expected
 overnight. Low temperatures will be tricky as locations which
 remain windy through the night won't be nearly as cold as what
 the NBM is forecasting. Case in point...the NBM forecast for
 Sandpoint is -11F whereas the MOS guidance is generally in the
 single digits above zero. Coeur d'Alene is similar with an NBM
 forecast of -10F and MOS values around -2F. Omak isn't quite as
 extreme with a  -4F NBM forecast and a 5F MOS forecast. Although
 we nudged these locations closer to MOS it will be cold no
 matter what verifies when computing the wind chill. Tonight wind
 chill values from Spokane to Bonners Ferry will bottom out in the
 -17f to -26f range with similar values in the Okanogan Valley and
  Waterville Plateau. These values will support the upgrading of
  the wind chill watches to wind chill warnings. Meanwhile in some
  of the more protected locations across north- central and NE
  Washington, winds won't be as much of a concern but the dry air,
  clearing skies, and rapid radiation potential will allow
  locations such as the Methow Valley, Republic, and Colville
  areas to plummet into the teens below zero. Since this is
  similarly cold to the wind chill areas we will just issue wind
  chill warnings to simplify the messaging of the cold
  temperatures. In either case, wind or not this is dangerously
  cold situation and protections should be put in place.
  Hypothermia and frostbite are likely without the proper
  clothing.

  Winds will begin to decrease slowly on Friday
  afternoon as the arctic air becomes fully established area.
  Nonetheless we will still see wind chill values in single digits
  to mid teens below zero. High temperatures will only peak in
  the single digits over most valley locations with mid teens in
  the LC Valley and lower Columbia Basin. Some records for cold
  high temperatures will likely fall including Spokane where we
  have a high around 2F the record is 3 set in 1909. Other records
  are possible in Omak 4F (4F set in 1911) and Pullman 5F (6F in
  1949). These temperatures are over 30F colder than normal for
  this time of year.

* Snow: This will remain a concern through the evening due to a
  complex setup. We are dealing with a very unstable air mass,
  mainly across the southern half of eastern WA into the southern
  half of the ID Panhandle. Part of the heavy snow will revolve
  around Puget Sound Convergence Zone which is delivering snow,
  some of it heavy at times in Wenatchee, Leavenworth and Stevens
  Pass. This should continue into the early evening. The other
  area of concern will be focused over SE WA into NC ID where the
  unstable air will combine orographic ascent and the approaching
  cold front. This will certainly result in bands of snow over
  these locations with possible snow squalls into the evening with
  the greatest risk over the Palouse, Blue Mountains, LC Valley
  and Camas Prairie. Snow intensities of 1-2" per hour could occur
  with these bands. The snow will likely vary significantly over
  small distances and placing the heavy bands will be near
  impossible. We will continue with the current batch of winter
  weather highlights with the heaviest totals likely over the
  Blues and Camas Prairie with amounts possibly ranging from 5 to
  10 inches. Any snow which falls will eventually be blown by the
  incoming winds from the front. Difficult travel conditions are
  likely in open areas. Adding to the travel issues, we are also
  looking at the possibility of some flash freeze conditions over
  the southern half of WA and the Idaho Panhandle. Any snow which
  falls during the daylight hours will melt before quickly
  refreezing overnight. fx

Friday Night through Thursday: Bitterly cold temperatures will
continue Friday night and Saturday morning. There is the potential
of some near or record breaking low temperatures. Also, our
temperatures will struggle to 'warm' into the double digits
Saturday afternoon. We could see record low high temperatures in
some places as well. The strong gusty winds will have subsided,
but winds around 10 to 15 mph will continue at times Fri night
through early Sunday across parts of the Okanogan Valley, Columbia
Basin, Spokane/CdA area and up Highway 95 to the Canadian border.
The wind chill warning will continue through Saturday morning, and
have expanded to include northeast WA, the Methow valley and an
advisory for the Moses Lake area. Additional highlights of
advisories or warnings for wind chills will likely be needed for
Sunday in some areas, but don't want to confuse the messaging.
Even though we have temperatures warmer Sunday morning, there
could be some locations that see colder or as cold temps compared
to Saturday. When the winds decrease, and our skies clear, is when
we could see our coldest temperatures, especially for locations
with snow on the ground.

Saturday we will see mostly clear to partly cloudy skies. The
wave that had a potential to impact our southern forecast area on
Saturday looks to stay south of the area, and only have a slight
chance of snow Sat night for SE WA and the southern ID Panhandle.

The forecast remains dry through Monday, and our temperatures will
start to slowly moderate. Temperatures will still be well below
average for the middle of January with high temps Monday in the
single digits and teens.

There are some discrepancies as we head into Tuesday and beyond.
The question becomes what happens to the ridge along the west
coast. Does the ridge axis move east a bit and protect us, or
will the axis remain along the coast and send waves down the
front side of the ridge into eastern WA and north ID? By
Wednesday there are 12% of the ensembles showing a deep trough
moving in from the north, but that 12% is all European models. 33%
keep the ridge strong, which is 90% of the GFS models. Then 36%
show a broad flatter ridge and 19% showing some northwest flow and
lower heights. Lots of potential scenarios. The basic idea is that
temperatures will continue to moderate up towards average, but
still be 5 to 9 degrees below average, and we will see an
increased chance of snow starting Tuesday afternoon and continuing
through the remainder of the forecast period. /Nisbet

&&

.AVIATION...

18Z TAFS: Intense snow associated with a compact upper level
disturbance tracked through the KGEG-KSFF-KCOE corridor right
around issuance time, however that feature has now pushed SE into
the central ID with periods of moderate to heavy snow expected
there with IFR conditions. For KGEG-KSFF-KCOE we will likely see
MVFR and occasional VFR conditions due to cigs. As a stronger
arctic front pushes in from the NE late this afternoon or early
evening we could see the reformation of snow showers and possible
IFR conditions but only light accumulations are expected. For KMWH
and KEAT primarily VFR conditions are expected with increasing
north winds however like the other sites there will be a small
chance of snow showers in KMWH with the arctic front this evening.
The toughest locations will be KPUW and KLWS which should see
southwest winds of 30-40 mph and some occasional snow showers
through early afternoon. Later this afternoon and evening as the
arctic front moves into these locations we should see a better
chance of MVFR and possible IFR conditions from snow. Several
inches of snow still look possible for KPUW and around an inch for
KLWS. It should be relatively light and fluffy snow which could
lead to blowing and drifting later tonight. Later in the TAF
period all sites, save KLWS will likely see VFR conditions with
clearing skies behind the arctic front. fx

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence
on the snow and arctic from moving through. Low to Moderate
confidence in snow squalls.

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

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        -1   2 -11   3  -4   9 /  30   0   0   0  10   0
Coeur d'Alene  -3  -1 -15   2  -7  10 /  30   0   0   0   0   0
Pullman         2   6  -9   8  -2  10 /  80  10   0  10  20  10
Lewiston       16  18   1  11   5  16 /  90  10   0  10  20  10
Colville       -8   2 -17   2 -11   9 /  10   0   0   0   0   0
Sandpoint      -3   1 -14  -1  -7   8 /  30   0   0   0   0   0
Kellogg        -4   2 -18   2  -9  11 /  70  20   0   0  10  10
Moses Lake      5  16  -1  10   2  16 /  20   0   0  10  10   0
Wenatchee       9   9  -2   6   1  14 /  40  10   0  10  10   0
Omak           -1   7  -7   6  -1  15 /   0   0   0   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory until 4 AM PST Friday for Coeur d'Alene
     Area-Lewiston Area-Northern Panhandle.

     Wind Chill Warning from 10 PM this evening to noon PST Saturday
     for Central Panhandle Mountains-Coeur d'Alene Area-Idaho
     Palouse-Northern Panhandle.

     Winter Storm Warning until 4 AM PST Friday for Central Panhandle
     Mountains-Idaho Palouse-Lewis and Southern Nez Perce
     Counties.

WA...Winter Weather Advisory until 4 AM PST Friday for Lower Garfield
     and Asotin Counties-Washington Palouse.

     Wind Chill Warning from 10 PM this evening to noon PST Saturday
     for Northeast Mountains-Okanogan Highlands-Okanogan Valley-
     Spokane Area-Upper Columbia Basin-Washington Palouse-
     Waterville Plateau-Western Okanogan County.

     Winter Storm Warning until 4 AM PST Friday for Western Chelan
     County.

     Winter Storm Warning until 10 AM PST Friday for Northeast Blue
     Mountains.

     Wind Chill Advisory from 10 PM this evening to noon PST Saturday
     for Moses Lake Area.

&&