Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 261154
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
354 AM PST WED NOV 26 2014

.SYNOPSIS...
Mild and breezy weather is expected today and Thanksgiving. By
late this morning, snow levels should rise above the mountain
passes. Motorists with plans to travel over the mountain passes
should experience good conditions this afternoon through Friday
afternoon. The arrival of a cold front Friday night into Saturday
will bring winter driving conditions to the mountain passes and
much cooler weather for the weekend.

&&

.DISCUSSION...

Today: The axis of the heaviest precipitation will continue to
migrate northward today as the jet stream is shunted Alberta and
Montana. Forecasting snow levels in the northern Cascades,
northeast Washington and far north Idaho over the last 24 hour has
been brutal. There has been a tremendously tight gradient between
snow levels of 6000 feet in places like Stevens Pass and the
valley floor in the Methow Valley. Fortunately this morning,
precipitation amounts will not be as heavy as they were yesterday
afternoon and evening. An additional 1 to 3 inches of snow
accumulation is expected this morning over the Pasayten Wilderness
to Sherman Pass to the mountains near Sandpoint. Another inch or
two of accumulation will also be possible early this morning over
Lookout Pass before snow transitions to rain shortly after
sunrise. Winter Weather Advisories will remain in effect through
10 AM for Lookout Pass and the northern portions of Stevens, Pend
Oreille, Bonner and Boundary counties.

The temperature forecast has been lowered along the East Slopes of
the Cascades, Waterville Plateau into the Moses Lake area. Thick
low clouds and fog will likely linger for a good portion of the
day. For the Palouse, West Plains and Ritzville areas, south winds
of 10 to 15 mph should develop by late morning providing mixing to
warm temperatures into the 40s and 50s.

Tonight into Thanksgiving: Snow levels will be at or above 6000
feet for Idaho and Washington tonight into Thanksgiving. Mountain
passes will experience periods of rain during this busy holiday
travel period, but the roads should be in relatively good shape.
Thanksgiving has the potential to be one of the warmest days of
the month. Despite mostly cloudy conditions, breezy southwest
winds will provide the mixing needed this time of year to push
temperatures into the 50s over much of the region. /GKoch

Friday through Sunday night...The region will start out under a
relatively warm and wet pattern Friday then transition to a much
colder but drier regime over the weekend. Westerly flow aloft will
continue to direct a moisture laden fetch across the region
Friday. The areas most favored for precipitation will be the
Cascade crest and the rising terrain north and east of the
Columbia Basin. The entire eastern half of the forecast area will
likely see a decent amount of precip as a surface low tracks south
from southeast British Columbia into central Idaho by Saturday.
Right now models are generally tracking it through the Idaho
panhandle but the precise track will determine how far west into
the basin the precip will extend. QPF could easily top an inch or
two for north Idaho as the low slowly sinks south. Snow levels
will start out quite high, ranging from 5k to 7k ft. Only the
highest peaks will see snow on Friday.

An arctic front will drop south across the forecast area Friday night
and Saturday, bringing in much drier and colder air, chasing
precip to the southeast zones by Saturday evening. Plunging snow
levels will allow accumulating snow for the southeast valleys with
possible winter highlight criteria being achieved, particularly
for the Camas Prairie on Saturday. Temperatures will plummet
Friday night with single digits for the typical cold spots in the
northern valleys. Most locations will see a 20 to 30 degree drop
overnight with only the southernmost valleys escaping freezing
temps. As the low drops south, the building arctic high over BC
will strengthen the surface pressure gradient between them. Winds
will increase down the north-south valleys and be funneled down
the Purcell trench and into the west Plains and basin. Expect wind
chill temperatures below zero in the Okanogan valley where the
strongest winds and very cold temps will prevail.

Cold conditions will continue Saturday night and Sunday with much
of the forecast area remaining dry. The exception will be the
southernmost counties where the surface front will stall. Surface
winds will diminish but remain northerly, reinforcing the cold air
in the valleys. Southwest flow ahead of the next Pacific trough
will result in strong warm air advection in the mid levels for
Sunday night into Monday. This layer of warm air overrunning the
resident cold air at the surface could bring mixed precipitation
to the Columbia Basin, Wenatchee Valley, L-C valley and possibly
as far north as the Spokane area. Temperature profiles for the
northern valleys appear to be cold enough to support all snow.
/Kelch

Monday through Wednesday: An active weather pattern is expected to
continue through this period. The GFS has been more consistent
with pushing warm moist air mass form the Southwest into the
region compared with the ECMWF which is depicting a dry Northwest
flow. This set up is expected to bring widespread precip to the
region. Snow for most locations in the Inland Northwest excluding
the rain for the Palouse and Camas Prairie areas through Tuesday
morning. A small ridge is expected to begin to build in the region
on Tuesday and bring a decrease in the precip Columbia Basin and
continues snow to the Cascades, Idaho Panhandle, and Canadian
Border regions. Temperatures are expected to range from upper 20s
for highs and low teens for lows. /JDC

&&

.AVIATION...
12Z TAFS: A 24 hour rain event over much of the Inland Northwest
has left a soup of low stratus and fog. Deep surface low pressure
approaching Vancouver Island today will produce increasing
southwest winds over southeast Washington which should bring some
improvement to ceilings. Fog and stratus should lift at
Lewiston and Pullman this morning. Low level wind shear has been
included at Pullman prior to 17z. Nearby Alpowa summit is gusting
to 40 mph and NAM forecast sounding show strong winds at 2000 feet
off the deck. Cold air damming along the East Slopes of the
Cascades into the Moses Lake area could make ceiling and
visibility improvements very slow to evolve. The 12z TAFS show a
gradual lifting of the cloud deck, but this may be optimistic
looking at the dewpoints over the southern Columbia Basin which
will be advected into the cold stable air trapped along the East
Slopes. /GKoch


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        45  42  50  40  45  26 /  80  30  30  20  80  60
Coeur d`Alene  44  41  48  40  44  27 /  90  30  30  20  90  70
Pullman        54  44  53  42  48  31 /  30  30  30  20  80  80
Lewiston       56  47  58  45  52  37 /  10  10  10  20  70  80
Colville       38  38  46  38  42  20 /  90  60  50  40  80  10
Sandpoint      39  38  45  37  41  25 / 100  70  60  50  90  50
Kellogg        43  40  44  38  40  29 / 100  60  70  70  90  80
Moses Lake     46  44  55  40  50  25 /  10  10  10  10  30  20
Wenatchee      43  42  50  41  47  27 /  10  10  10  20  30  10
Omak           38  38  46  35  40  14 /  50  30  30  30  50  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory until 10 AM PST this morning for Central
     Panhandle Mountains-Northern Panhandle.

WA...Winter Weather Advisory until 10 AM PST this morning for
     Northeast Mountains.

&&

$$




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