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Forecast Discussion for Spokane, WA

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FXUS66 KOTX 151055
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
255 AM PST Fri Dec 15 2017

.SYNOPSIS...
Snow will spread over much of the Inland Northwest today. The
heaviest accumulations will be over southeast Washington and the
southern Idaho Panhandle. It will be drier for Saturday before
another weak weather system brings light snow on Sunday. A
stronger and wetter system arrives next Tuesday into Wednesday.

&&

.DISCUSSION...
Today through Saturday Night: Localized light snow falling from
the low clouds this morning, most notably over the West Plains of
Spokane. Pavement was already cold so this dusting of snow
shouldn`t impact roads much. The main frontal band of snow is
currently over NW Washington at 2:30am. It will move into the
Cascades by sunrise. At 10am, the band should extend from
Sandpoint to Ellensburg. This should mean a start time in the
Spokane metro area just before noon. By this time, road pavement
temperatures will probably around 35F, so initially the snow will
melt on the roads. But if it snows hard enough, there will be
road accumulations. North of Highway 2 it should be cold enough
for the roads to accumulate snow.

A mixed bag of precipitation types (snow, sleet, freezing rain) is
possible from Wenatchee to Moses Lake and southward, mainly this
morning and early afternoon. This could lead to slick roads and
side walks but won`t be enough ice to cause tree or power line
problems.

The front will slowly exit over southeast WA and the southern
Panhandle tonight. This is the favored area for snow accumulations
with this flow pattern. As such, winter weather advisories have
been issued for the Palouse, central Panhandle, L-C valley, and
the Camas Prairie. Saturday should be dry but cold and cloudy. RJ

Sunday through Thursday: Active weather pattern continues. The ridge
is rather flattened and easily over-topped by disturbances
running over it and pushing moisture through it Sunday through
Tuesday morning. With this in mind pops will still paint a good
possibility of valley rain and mountain snow with a rain shadow
expanding in the lee of the Cascades into the Columbia Basin and
points further east at times Sunday through Tuesday morning.
Models depict a shortwave digging on the back of a baroclinic band
with moderate amounts of precipitable water running through it
Tuesday and pass the resulting low pressure system aid its
associated frontal features through Eastern Washington and
Northern Idaho in the Tuesday/Wednesday time interval. This is
followed up with ridge axis positioning well off the coast
allowing for a cold northerly flow Thursday which appears void of
significant shortwaves in the latest models. As far as how this
plays out with temperatures it should allow for a warming trend
maxing out on Tuesday as the low pressure system works through
followed by a cooling trend brought about by the northerly flow
that follows after. Winds could be breezy Tuesday due to the low
pressure systems surface low positioning in Southern British
Columbia bringing about a tight south to north pressure gradient
followed by a shift to breezy southwest winds Wednesday when the
back edge of the same low pressure system passes through. /Pelatti


&&

.AVIATION...
12Z TAFS: Stratus and fog in the lower elevations will be overrun
by a frontal system today. The front will be aligned from
Sandpoint to Ellensburg by 18Z, and exiting the southern Panhandle
overnight. KEAT and KMWH could see a mixed-bag of precipitation
types. For the remainder of the TAFs it should be just snow with
IFR conditions this afternoon and evening. RJ

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  25  30  25  34  31 / 100  10   0  20  40  40
Coeur d`Alene  33  27  30  23  34  31 / 100  20  30  20  60  70
Pullman        32  27  30  23  34  32 / 100  60  40  10  30  70
Lewiston       35  30  36  25  38  35 /  80  80  20  10  20  50
Colville       33  23  33  26  32  29 /  40  10   0  30  40  30
Sandpoint      32  27  32  24  33  30 /  80  40  20  20  60  80
Kellogg        31  25  28  21  31  29 / 100  80  50  10  50  90
Moses Lake     31  27  35  27  36  30 /  40   0   0  10  20  10
Wenatchee      35  30  37  28  35  30 /  20   0   0  20  30  20
Omak           33  26  34  27  32  28 /  10   0   0  30  30  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory until 10 AM PST this morning for Central
     Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-Lewis
     and Southern Nez Perce Counties-Lewiston Area-Northern
     Panhandle.

     Winter Weather Advisory from 1 PM this afternoon to 4 AM PST
     Saturday for Central Panhandle Mountains-Idaho Palouse-
     Lewiston Area.

     Winter Weather Advisory from 1 PM this afternoon to 7 AM PST
     Saturday for Lewis and Southern Nez Perce Counties.

WA...Air Stagnation Advisory until 10 AM PST this morning for East
     Slopes Northern Cascades-Lower Garfield and Asotin Counties-
     Moses Lake Area-Northeast Blue Mountains-Northeast
     Mountains-Okanogan Highlands-Okanogan Valley-Spokane Area-
     Upper Columbia Basin-Washington Palouse-Waterville Plateau-
     Wenatchee Area.

     Winter Weather Advisory from 1 PM this afternoon to 4 AM PST
     Saturday for Lower Garfield and Asotin Counties-Washington
     Palouse.


&&

$$

NWS Spokane, WA (OTX) Office Area Forecast Discussion

Discussion Script by Ken True at Saratoga Weather - WFO Script by SE Lincoln Weather