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000 
FXUS66 KOTX 252234
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
234 PM PST Sat Feb 25 2017

.SYNOPSIS...
Snow will return to the Inland Northwest tonight, Sunday, and
Monday. A prolonged period of snow showers will have the potential
to produce significant accumulations for the Idaho Panhandle and
portions of southeast and east central Washington. Chilly
temperatures will linger through Tuesday. A windy and milder weather
pattern will be possible Wednesday through Saturday.

&&

.DISCUSSION...
Tonight...The next system clearly visible on IR/water vapor
satellite imagery over British Columbia will drop south into
Washington and north Idaho tonight. Models show some strengthening
of this system as a surface low deepens from 1013mb near the
central BC coast this afternoon...to 1005mb as it nears the north
Washington coast late tonight. Moist isentropic ascent will
increase tonight...maximized across NE Washington into the Idaho
Panhandle where 1-2 inches is likely by early morning. However the
air mass will be cold enough that most places should receive light
snow...beginning over the northern mountains and Cascade crest this
evening...spreading south into the Upper Columbia Basin...Spokane/Coeur
d'Alene area...palouse...and Central Panhandle Mountains 
overnight. JW

Sunday through Tuesday night: Main story will be snow, a prolonged 
light snow event that will develop late tonight into Sunday turn 
more convective through early next week. Watching the next weather
disturbance dropping in from the north and spinning up a surface 
low on the WA/OR coast. A surface boundary will straddle the 
Inland NW from west to east with good low level convergence. 
Isentropic lift will increase through the day with good lift in 
the dendritic layer. Snow levels will be low with snow a good bet 
in all areas through the morning. By Sunday afternoon, the cold 
pool aloft shifts over northeast Washington while surface 
temperatures begin to rise to or slightly above freezing. The air 
mass will become more convective in the afternoon and evening with
snow banding possible. The track and set up of these bands is 
highly variable and looks like the best area will range from Deer 
Park to Athol south to Pullman to Deary, putting the Spokane/Coeur
d'Alene area right in the cross hairs. It will take on early 
spring like conditions. Shower activity will decrease slightly 
Sunday night, but return again for Monday. The snow showers 
coupled colder overnight lows with lead to refreezing of the 
roadways by Monday morning which could increase impacts across 
extreme eastern Washington into north Idaho. Surface temperatures 
will rise again to near or slightly above freezing by Monday 
afternoon and snow showers will decrease slightly Monday evening. 
Orographic lift will support snow showers across southeast 
Washington into the central ID panhandle into Tuesday. Shower 
activity is forecast to decrease Tuesday afternoon with evening 
with high pressure over the region. The flow aloft will become 
more northwesterly will moisture streaming aloft and bringing a 
threat of light mountain snow to the north late Tuesday night. 

Snow: 24 hour snowfall totals will range from 1-2 inches in the
valleys of north central Washington with 4-8 inches in mountains
for tonight into Sunday, with no winter highlights are expected.
Across the eastern third of Washington into north Idaho, 2-5
inches are more likely tonight into Sunday and winter weather
advisories will cover this, starting from north to south tonight.
Persistent snow showers Sunday night into Monday will bring
another 2-4 inches of snow for southeast Washington into the
central Idaho panhandle. The advisories will decrease from west to
east Monday into Tuesday. /rfox. 

Wed through Saturday: Much of our focus was on Wed, with N Idaho
snow and winds for much of Ern Wa and Cascade higher elevations
our primary concerns. Under broad ridging with a prolonged decent
moisture fetch over the region south of the jet, increasingly 
veered flow and will not only produced moderate snow accumulations
for the the N Idaho Mtns but will also produce a wide lee-
Cascades pcpn shadow that should keep much of the Upper Columbia 
Basin dry, though windy. Mtn wind gusts could exceed 50 mph. 
Valley snow accumulations are possible for the N Id Panhandle Wed
morning as well. Snow, rain, and windy conditions for all but the
lower Basin zones will be less of an issue until another 
potentially very windy and snowy wave moves in for next weekend. 
bz

&&

.AVIATION...
00Z TAFs: A stratocumulus deck this afternoon with areas of MVFR
conditions over NE WA/N Idaho will dissipate early this evening
with the loss of daytime heating. The next system arrives tonight. Snow
will develop late this evening into the overnight hours for the 
region from north to south. The most steady snow with lower 
visibilities is expected at Spokane, Coeur d'Alene, Sandpoint, and
Pullman. 1 to 3 inches is expected at these airports by 18z 
Sunday with additional light snow likely into the afternoon. For 
KEAT/KMWH up to an inch is expected through 18z Sunday...while at
KLWS marginal temperatures for accumulating snow may result in 
only a dusting. JW

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        24  33  24  33  20  33 /  90 100  60  60  30  10 
Coeur d'Alene  24  33  23  34  17  34 /  90 100  70  70  30  20 
Pullman        26  34  24  35  23  35 /  70 100  60  70  80  60 
Lewiston       29  37  27  40  28  41 /  30  90  60  60  70  60 
Colville       21  34  18  34  18  35 /  50  80  60  30  10  10 
Sandpoint      22  32  23  33  18  33 /  90  90  70  60  40  20 
Kellogg        22  31  25  32  21  33 /  90 100  80  80  80  60 
Moses Lake     27  38  23  38  21  40 /  50  90  60  20  20  10 
Wenatchee      24  37  24  36  22  38 /  30  80  40  20  20  10 
Omak           20  35  20  35  19  35 /  50  60  30  20  10  10 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory from 9 PM this evening to 3 PM PST 
     Monday for Northern Panhandle. 

     Winter Weather Advisory from midnight tonight to 10 AM PST 
     Tuesday for Central Panhandle Mountains-Idaho Palouse. 

     Winter Weather Advisory from 4 AM Sunday to 10 AM PST Tuesday 
     for Lewis and Southern Nez Perce Counties. 

     Winter Weather Advisory from 4 AM to 3 PM PST Sunday for 
     Lewiston Area. 

     Winter Weather Advisory from midnight tonight to 3 PM PST Monday 
     for Coeur d'Alene Area. 

WA...Winter Weather Advisory from 9 PM this evening to 3 PM PST 
     Monday for Northeast Mountains. 

     Winter Weather Advisory from midnight tonight to 10 AM PST 
     Tuesday for Washington Palouse. 

     Winter Weather Advisory from 4 AM Sunday to 10 AM PST Tuesday 
     for Northeast Blue Mountains. 

     Winter Weather Advisory from 4 AM to 3 PM PST Sunday for Lower 
     Garfield and Asotin Counties. 

     Winter Weather Advisory from midnight tonight to 3 PM PST Monday 
     for Spokane Area. 

     Winter Weather Advisory from 9 PM this evening to 3 PM PST 
     Sunday for Okanogan Highlands. 

     Winter Weather Advisory from midnight tonight to 3 PM PST Sunday 
     for Upper Columbia Basin. 

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