Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 272337
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
337 PM PST TUE 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 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 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...
00Z TAFS: A moist boundary layer trapped under an inversion with
no weather systems strong enough to disturb the near surface layer
will promote continued widespread IFR and LIFR conditions at or
near all TAF sites through the next 24 hours. The KGEG and KPUW
and KLWS TAF sites will experience a brief period of VFR
conditions this evening while mid level cloud cover exists but
after 06Z this cloud cover will thin and allow radiational cooling
to drop temperatures back to saturation and return fog and stratus
to these sites. Moderate improvement is possible after 21Z
Wednesday but this is a low confidence forecast. KMWH and KEAT in
the deepest stagnant air will likely remain under IFR and LIFR
conditions through the TAF period. /MJF

&&

.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...
ID...None.
WA...None.
&&

$$



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