Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 220007
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
407 PM PST Tue Feb 21 2017

.SYNOPSIS...The last in a series of wet weather systems will
exit the Inland Northwest tonight. Cooler and showery weather is
forecast through the weekend.


&&

.DISCUSSION...

Tonight: Our precipitation band will make a gradual exit from west
to east tonight. Precipitation type with this system has been
complicated since it arrived early this morning, and it promises
to be difficult as it departs this evening. Precipitation began
as rain in Pullman this morning, and has changed to snow this
afternoon. The opposite occurred in Spokane and Coeur d`Alene as
we started as snow in the morning and transitioned to rain in the
afternoon.

Cooler air wrapping around the departing surface low will drive
snow levels down this evening and through the night. As the sun
goes down and surface low pressure complete its transition east of
the Continental Divide, we should see snow levels fall toward the
valley floors. It will be interesting to see where snow level
fall quickly enough for accumulations before the precipitation
shield translates out of the region. Looking at the 18z runs of
the GFS and NAM, it looks like the Pullman, Moscow, Plummer and
Coeur d`Alene areas will have a decent shot of an inch or two of
wet accumulation early this evening. Places that get snow to stick
this evening have the potential to be very slick as road surfaces
and air temperatures fall below freezing overnight. A Winter
Weather Advisory has been issued for the Central Idaho Panhandle
where our confidence of significant accumulations are the highest.
It has been snowing all day at Fourth of July and Lookout Pass,
but roadway accumulations have been slushy at best this afternoon.
As snow levels tumble this evening and pavement temps fall around
sunset, I-90 will have a very good chance of becoming snow
covered especially for elevations above 3000 feet.

Wednesday: Our transition from a relatively "mild and moist"
southwest flow to a cooler and showery northerly flow will occur
on Wednesday. While our daytime highs tomorrow may be a bit
warmer than today, our temps aloft will become colder. With less
wind, colder air aloft, and lower overall moisture in the
atmosphere, our low temperatures will become colder the next few
days. Good news for flooding since our snowmelt will decrease. Bad
news for potholes on our roads as we enter a pattern of above
freezing temps during the day and sub-freezing temps at night.
/GKoch

Wednesday Night through Saturday Night: General troughiness
remains across much of the western US. The track of stronger
weather disturbances through the end of the work week and into the
weekend is mainly to the south of the Inland Northwest. However
weak waves will move through and provide a chance of snow showers
at times through the period. There really is no dry period per
say, but most of the showers should remain confined to the
mountains and their adjacent valleys. Temperatures will remain
below average for this time of the year. Daytime temps in the 30s
and overnight lows in the teens to lower 20s is expected. /Nisbet

Sunday through Tuesday: Another Low is expected to impact the
region during this period. Models are not in good agreement with
the where the Low will track. The Low will push in from the
Northwest and bring colder air. This is expected to bring snow to
most of the region. The Columbia Basin will see a rain snow mix
during the day with mainly snow overnight with mountains staying
snow through the event. Temperatures will fluctuate above above
to below freezing during the event, bringing a thaw freeze event
leading to slick surfaces during the early morning hours. /JDC

&&

.AVIATION...
00Z TAFs: Snow this evening at Pullman will have the potential to
produce slushy accumulations up to an inch at Pullman. Low clouds
and fog will likely follow the departure of our band of
precipitation this evening. As our surface low pulls east of the
Continental Divide, our region will undergo a good deal of mid-
level drying and cooling, but fresh precipitation and moist
surface dewpoints will probably keep low stratus and possibly fog
in Spokane, Coeur d`Alene, Sandpoint, and Bonners Ferry at least.
Low level southwest flow favors stratus or fog at these airports.
/GKoch

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        26  37  21  35  19  34 /  60  10  10  10  10  20
Coeur d`Alene  28  37  19  35  17  35 / 100  20  20  20  10  20
Pullman        30  38  22  35  20  36 /  90  10  10  30  20  20
Lewiston       34  44  28  41  25  41 /  70  20  10  20  20  20
Colville       24  40  21  37  18  36 /  30  10  20  20  10  20
Sandpoint      28  37  21  35  18  33 /  70  30  20  20  20  20
Kellogg        28  35  22  34  20  33 / 100  30  30  40  20  30
Moses Lake     23  38  21  36  20  35 /  10   0   0  10  10  20
Wenatchee      25  36  22  34  20  33 /  10  10  10  10  10  20
Omak           22  36  21  33  19  32 /  20  10  10  10  10  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Flood Watch through Wednesday afternoon for Central Panhandle
     Mountains-Coeur d`Alene Area-Idaho Palouse.

     Winter Weather Advisory until 7 AM PST Wednesday above 3000 feet
     for Central Panhandle Mountains.

WA...Flood Watch through Wednesday afternoon for Spokane Area-
     Washington Palouse.

&&

$$



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