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Area forecast discussion 
National Weather Service Spokane Washington
218 PM PST Tuesday Jan 27 2015

Synopsis...
areas of low clouds and fog will persist across portions of
inland northwest as high pressure remains in place. A couple of
weak storm systems will affect the area tonight and on through
Thursday and bring a small chance of showers and cooler temperatures
to the region. A ridge of high pressure will then rebound late in
the week for drier weather and more fog, before breaking down next
weekend. The next best threat of precipitation, including possible
rain and snow, arrives on Sunday and beyond.

&&

Discussion...

Tonight and tomorrow...fog and low clouds continue to be
problematic as a somewhat weakened ridge of high pressure remains
in place over the area. A weak front over-tops the ridge and
flattens it temporarily with little, if any, in the way of
substantial precipitation expected with the front passage.
Boundary layer moisture still of a high enough quantity to allow
for a repeat of the past night with re-intensification of fog and
low clouds overnight and into tomorrow morning over many lowland
and valley locations with the exception being lowlands south of
Spokane such as Pullman and vicinity where lower level winds from
the east have helped dry it out and keep conditions down there
clearer and warmer in comparison. /Pelatti

Wednesday night through Saturday...in general models are in good
agreement in maintaining a mean ridge over the northwest.
Thursday a weak wave will transit across the forecast area west
to east...fueled by a parcel of 1/2 inch precipitable water which
will be disconnected from any Pacific tap by this time. In favor
of the necessary lift for any precipitation with this wave will be
some differential vorticity dynamics and a weak 500 mb
front...however the wave will be weakening as it transits and the
overall ridge will be building aloft and there is no detectable
reflection of this wave near the surface. Thus...will handle this
disturbance with a chance of sprinkles across the southern tier of
zones on Thursday with a slight chance of real showers over the
Panhandle mountains. Otherwise these is really nothing of note to
the stagnant deep winter inversion pattern which will keep patchy
fog...at least locally dense each morning with near or slightly
below freezing temperatures creating the Prospect of some slick
Road conditions...and areas of low stratus decks with temperatures
near or slightly above normal through the beginning of the
weekend.

Saturday night through Tuesday...for a couple of days now both the
GFS and European model (ecmwf) models have been hinting at a general ridge breakdown
and a return to a more active pattern. Today these models continue
this agreement although there are some serious differences with
the character of this breakdown especially after Monday. In the
mean time both models suggest the first significant storm system
will impact the region on or about Sunday and most likely (at
this time) Sunday night with a deep and rich feed of Pacific
moisture and a probably frontal complex to enhance this fetch.
Snow levels during this initial break down will probably remain
quite high. Forecast pops will increase starting Sunday and
remain elevated through the remainder of the extended term. The
best chance for appreciable periods of valley/basin rain and
mountain snow will be over the eastern half of the forecast area
with the deep basin and Cascades Lee zones benefiting from the
typical rain shadow effect but still under threat for some light
rain. After Monday the European model (ecmwf) advertises a decidedly colder
solution than the GFS and may Herald a return of actual winter-
like weather. This is too far out to engender any significant
confidence at this time...but confidence is quite high for the
overall pattern change to a more progressive pattern after
Saturday. /Fugazzi

&&

Aviation...
18z tafs: light freezing drizzle and freezing fog noted to
address the light ice accumulation this morning where the fog is
most prevalent is on the decrease for the most part this morning
as temperatures warm, still some fog and low clouds is likely to
stick around in many a valley and lowland location. Elsewhere
there are enough upper level clouds passing through the ridge of
high pressure to keep various sky cover at times in the remaining
aviation forecasts not impacted by the low stratus and fog.
/Pelatti

&&

Preliminary point temps/pops...
Spokane 31 41 32 42 31 40 / 0 0 0 10 0 10
Coeur D'Alene 33 41 33 42 31 41 / 10 10 0 10 10 10
Pullman 37 49 36 46 34 42 / 10 10 0 10 0 10
Lewiston 39 54 38 50 36 47 / 10 10 0 10 0 10
Colville 30 38 31 39 28 39 / 0 0 0 0 0 10
Sandpoint 30 40 29 40 29 40 / 10 10 10 10 10 10
Kellogg 33 42 32 43 31 41 / 10 10 10 10 10 10
Moses Lake 32 41 33 43 31 41 / 0 0 10 0 0 10
Wenatchee 33 41 33 43 33 42 / 0 0 10 0 0 0
Omak 31 37 29 38 29 39 / 0 0 0 0 0 10

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...none.
&&

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