280 
FXUS66 KOTX 060519
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1019 PM PDT Sat Nov 5 2022

.SYNOPSIS....

Another winter storm will move into over the region on Sunday with
heavy snow expected across north-central Washington. Low land snow
will spread eastward into Idaho Sunday night into Monday morning
impacting the morning commute. Brisk north winds with cold wind
chills on Tuesday. Cold temperatures with lows down into the
single digits and teens will continue through the work week before
slowly moderating next weekend.

&&

.DISCUSSION...
Tonight through Monday: A very unstable, post-frontal airmass 
remains over the Pacific Northwest this afternoon. Looking at the
SPC Mesoanalysis, low level lapse rates of 9 C/km along with CAPE
values to around 250 J/kg are supporting numerous showers across 
eastern Washington and the Idaho Panhandle. Any showers will be 
capable of producing quick bursts of moderate to heavy 
snow/rain/graupel along with isolated strikes of lightning 
through the early evening. Roads will become slick under these 
heavier showers.
 
The well-advertised strong upper level is currently located near the 
central BC coast and will continue to slide down the coast tonight. 
Precipitation associated with this low will begin late tonight 
morning over central Washington. Strong dynamics along with a 
surface level wind shift to the northeast, enhancing the upslope 
flow along the east slopes of the Cascades, will support heavy 
snow across the north Cascades, the Okanogan valley, and the 
Okanogan Highlands tonight through tomorrow. Significant snow 
amounts are expected for locations such as the Methow Valley and 
the Okanogan Valley where models have been hitting these areas 
hard for the past several days. A previously mentioned challenge 
was the fact that Sunday afternoon will feature rising snow levels
as a warm front moves northward, but under these heavy snow 
amounts across the Okanogan valley, I do think it will be hard to 
see much warming during the day Sunday for these northern areas, 
which would support higher snow accumulations. Snowfall 
probabilities through 10AM Monday from the National Blend of 
Models (NBM) reveals

-Omak: 70% chance to see over 6 inches of snow, a 50% chance to see 
over 8 inches, and a 20% chance to see over 12 inches.

-Methow Valley: 90% chance to see over 6 inches of snow, 80% chance 
to see over 8 inches, and a 60% chance to see over 12 inches of 
snow. 

Winter Storm Warnings look good and will be in effect from 4am 
Sunday through 10 AM Monday. Precipitation will spread east through 
the day Sunday with a change to rain or a rain/snow mix as
temperatures warm above freezing for the Wenatchee area, the 
Basin into the Spokane area, Palouse and southward. Uncertainty 
still remains in the snow totals during the day on Sunday, but 
precipitation does look to transition to all snow by Sunday 
evening as an Arctic front begins to push south. The heaviest snow
Sunday night into Monday will be across the northeast mountains 
and north Idaho where colder temperatures support higher snow 
ratio amounts. Across these areas through 10AM Monday, the NBM has

Spokane: 60-70% chance to see snow over 2 inches of snow and a 20% 
chance to see over 4 inches.

Pullman: 40% chance to see over 2 inches and 10% chance to see over 
4 inches.

Sandpoint: 80% to see over 2 inches, and a 60% chance to see over 4 
inches. 

Highs on Monday will be much colder with the Arctic front passage 
with highs dropping into the 20s to mid 30s and lows in the teens to 
low 20s with single digits across our northern valleys. Breezy 
northeast winds will result in very cold wind chills Monday morning. 
/vmt

Tuesday through Wednesday: The Inland Northwest will be under a
trough of lower pressure through the middle part of the week. All
of the dynamics associated with this trough will dive south of the
region primarily into California, Nevada, and into southern 
Idaho. The National Blend of Models has a 10-30 percent chance for
snow from the Northeast Blue Mountains to the Camas Prairie and 
southern to central Idaho Panhandle Tuesday night into Wednesday 
morning. The 12Z model guidance has decreased these chances a bit 
though with a dry forecast the most likely scenario. Breezy north 
to northeast winds is expected down the Okanogan Valley and the 
Purcell Trench for Tuesday morning with sustained speeds of 10 to 
20 mph and gusts as high as 25 to 35 mph. The northeast winds will
spread out over the northern Columbia Basin and into the Moses 
Lake Area. Low temperatures for Tuesday will dip down into the 
single digits across the northern mountain valleys including the 
Methow Valley over to Republic, Colville, Northport, and Bonners 
Ferry to Sandpoint. The brisk northerly winds will result in wind 
chills down to near zero through the Purcell Trench in the 
Northern Panhandle.

Wednesday night through Saturday: A shortwave ridge of higher
pressure will build in behind the exiting trough. Mid to high
level clouds look to clear out setting up for more cold nights
with lows in single digits and teens, but winds will be weaker
with pressure gradients relaxing across the region. Weaker winds
and strong radiational cooling figures to set up the potential for
fog across the mountain valleys and into the northern basin across
the Highway 2 corridor. Temperatures will be below normal through 
the week into next week. There is a small chance for a weak 
weather system to impact the region over the weekend, otherwise 
there aren't any impactful weather systems that will bring much in
the way of precipitation through the rest of the week after 
Monday. /SVH

&&

.AVIATION... 
06Z TAFS: Convective rain and snow showers will continue to exit
the Idaho Panhandle overnight. The snow showers associated with
the Puget Sound Convergence Zone will also wane as the mid-level
flow weakens ahead of the incoming low. Our next round of
precipitation will spread into the Cascades between 12-15z and
into Wenatchee, Chelan, and Omak between 15-18z. Visibility as low
a half mile with moderate snow will be possible at Wenatchee 
during the mid to late morning. Look for the precipitation band to
make slow progress to the east Sunday and Sunday night with VFR
conditions at Spokane, Coeur d'Alene, Pullman, and Lewiston until
mid to late evening Sunday. /GKoch

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        27  42  21  31  14  28 /  10  30  80  60  10   0 
Coeur d'Alene  26  40  20  30  14  29 /  10  20  70  70  10   0 
Pullman        27  42  25  36  16  32 /  10  10  80  50  10   0 
Lewiston       34  48  33  41  26  36 /  10  10  80  50  10   0 
Colville       15  37  10  31   4  30 /  10  50  80  60  10   0 
Sandpoint      25  35  13  26  12  25 /  20  30  60  80  10   0 
Kellogg        25  38  22  28  11  27 /  30  10  60  70  10   0 
Moses Lake     29  45  23  39  20  32 /  10  60  70  30  20  10 
Wenatchee      31  38  26  36  23  30 /  20  70  70  40  30  10 
Omak           25  34  23  36  16  34 /  10  80  80  60  20   0 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Storm Warning from 4 AM Sunday to 10 AM PST Monday for 
     Northeast Mountains-Okanogan Highlands-Okanogan Valley-
     Waterville Plateau-Western Okanogan County.

     Winter Weather Advisory until 10 PM PST Sunday for Central 
     Chelan County-Wenatchee Area.

     Winter Weather Advisory until 10 PM PST Sunday for Western 
     Chelan County.

&&

$$