Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 301145
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
345 AM PST FRI JAN 30 2015

.SYNOPSIS...
Areas of low clouds and fog will persist across portions of
Inland Northwest as high pressure remains in place. The ridge of
high pressure will begin breaking down Sunday. This will result in
and increased chance for valley rain and mountain snow through
the middle of next week.



&&

.DISCUSSION...
Today through Saturday...Quiet weather will prevail during
this period...but there is a subtle feature which will approach
later tonight into early Saturday which could deliver some
weather. For today the weather will be about as mundane as weather
can get during this time of year in the Inland Northwest. Upper
level high pressure will once again remain fixed over the region
with the jet stream poised over central BC. Meanwhile a fairly
broad area of high pressure will reside near the ground resulting
in very light winds and hence very poor mixing potential. This
suggests the fog and stratus currently over most elevations below
3500 feet per the latest fog product will persist longer into the
day. For locations west of a line from Colville to Pullman...the
odds of the clouds breaking up are rather slim as the stratus
there is most likely thicker than the deck east of this area. This
was the approximate line which delineated the clearing line late
yesterday afternoon. East of the line the prospects of a breakup
are a little better...since we suspect the deck is shallower
however confidence is far from good. This area was subject to
rapid fog development during the evening and much of it was dense.
Lately though the fog has been lifting across the Idaho Panhandle
and even the Spokane Valley into the Coeur d`Alene area. We
currently have a dense fog advisory in effect for a large portion
of the Idaho Panhandle and across the eastern quarter of
Washington, however if this lifting trend continues we will have
to drop a good portion of them.

For tonight and into early Saturday the weather gets a little more
"exciting". This excitement will be in response to a shortwave
trough currently situated near 50n/130w. All models are doing well
with its placement compared to satellite and all take the feature
through BC today before diving it southeast into NW Montana late
tonight into early Saturday. Deep moisture won`t likely accompany
this feature...however it will likely induce some weak upward
motion through the ever-present low-level cloud deck. This will
likely provide the impetus for some drizzle (or possibly flurries)
across far eastern Washington and much of the Idaho Panhandle.
Temperatures will be close to freezing so we would likely see a
mix of drizzle and freezing drizzle. Roads could get slick but
confidence in drizzle forecasts is quite low so will cover
situation via social media rather than a weather highlight. The
threat of drizzle and freezing drizzle should wane rapidly during
the afternoon as the shortwave trough shears apart into northern
Wyoming and lowers the ascent through the saturated boundary
layer. fx

Saturday night through Thursday: The region transitions to a
wetter pattern. The system that christens the transition, a
organized frontal wave, makes its way in with a subtropical
moisture tap Sunday. Strengthening isentropic ascent with the
leading warm front and that deepening moisture will lead to
increasing precipitation chances. Some of that lift/moisture combo
starts into the Cascades and northern mountains Saturday night
late, but the stronger threat and more likely precipitation comes
in between Sunday and Sunday night.

* Precipitation-type: On Sunday morning light snow accumulations will
  be possible down to the valley floors, largely away from the
  deeper Basin to lower Palouse and L-C Valley. By Sunday
  afternoon and evening the snow threat in the valleys retreats
  north of Highway 2, though some snow may still mix with the rain
  threat about the southern hills around the Spokane/C`dA area.
  And where snow may continue in the northern valleys
  accumulations may be limited with the heating of the day.

* Snow amounts: light to moderate snow accumulation are possible
  in the mountains above about 3000 to 4000 feet. Here some 2 to 5
  inches are possible between from Sunday morning to Monday
  morning, with local amounts near 8. This may impact locations
  such as Lookout Pass, Sherman Pass and Stevens Pass.
  Accumulations about the valleys are expected to be lighter. The
  Cascade valleys, north of Lake Chelan, and northeast WA and
  north ID valleys could see 1 to 2 inches, with local amounts
  near 3 inches. Other areas such as the Waterville Plateau to the
  Spokane/C`dA area, and the higher Palouse (north of Pullman)
  could see anywhere from a trace to a half inch, with isolated
  amounts to 1 inch.

On Monday a second wave comes in and keeps the precipitation
threat high, at least away from the lee of the Cascades and
deeper Columbia Basin. Current timing suggests the higher threat
with this second wave comes in Monday afternoon and evening,
though the threat may not really end across the central Panhandle
Mountains after Sunday`s system. By this time snow levels look a
bit higher, between 2.5 and 5.0kft, lowest toward the northern
mountains. So more of valley rain and mountain snow event is
projected. However a rain/snow mix cannot be ruled out along and
north of highway 2 in the morning and night hours.

From Tuesday to Thursday the region remains in a more progressive
pattern, with the passage of occasional shortwaves with
intermittent wet and dry periods. Through the period the highest
threat will be in the windward facing slopes, i.e. the Cascade
crest and the northeast WA and ID panhandle mountains.
Occasionally the threat will ramp up across the valleys and basin
areas, tied to the precise timing of those waves. However model
consistency on that point is poor. Loose agreement suggests a
drier period between Tuesday and Wednesday, or at least a shift of
the higher precipitation threat toward the WA/OR border and lower
Panhandle southward, before the threat rises again toward
Thursday. Look for a continued valley rain and mountain snow
threat during the day, with a possible rain/snow mix in the
valleys during the night and morning hours. /J Cote`


&&

.AVIATION...
06Z TAFS: Light winds and clear skies aloft will continue to bring
widespread restrictions from fog and stratus through the next 24
hours. Fog will impact KGEG/KSFF/KCOE/KPUW and possibly KLWS
while KEAT/KMWH will largely contend with stratus. Minor
improvements will be noted at all sites as the fog lifts to more
of a stratus deck midday, but all sites will stay in IFR or MVFR
conditions. The stratus is expected to lower once again late
evening as low level inversions strengthen. Some light drizzle
late in the evening for the KGEG/KSFF/KCOE sites will be possible
as a weak shortwave passes to our north. Overnight expect the
return of IFR/LIFR conditions. /Fliehman


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        36  30  37  29  37  33 /   0  10  10  10  60  50
Coeur d`Alene  39  31  39  29  37  32 /   0  10  10  10  60  60
Pullman        39  31  44  33  42  37 /   0  10  10  10  60  60
Lewiston       42  33  47  34  46  38 /   0  10  10  10  40  50
Colville       40  32  36  29  36  31 /   0  10  10  20  60  50
Sandpoint      36  30  36  27  36  30 /   0  10  10  20  70  70
Kellogg        39  30  39  29  37  33 /   0  10  10  10  70  70
Moses Lake     39  32  40  30  40  32 /   0   0   0  10  20  20
Wenatchee      39  32  39  30  40  33 /   0   0   0  20  30  20
Omak           36  32  36  30  38  31 /   0   0   0  20  40  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Dense Fog Advisory until 1 PM PST this afternoon for Coeur
     d`Alene Area-Idaho Palouse-Northern Panhandle.

WA...Dense Fog Advisory until 1 PM PST this afternoon for Northeast
     Mountains-Spokane Area-Washington Palouse.

&&

$$



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