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Area forecast discussion 
National Weather Service Spokane Washington
933 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...
second update this evening to fine tune wx grids, adjust
temperatures, and add drizzle. Still looks as if worse
visibilities remain along the northern Idaho Panhandle and
Columbia Basin across portions of Lincoln and Adams counties. Low
clouds and fog have moved into the West Plains, Palouse, and look
to continue east into the Idaho Panhandle with cd'a now reporting
some stratus fragments but visibilities have not been below 1/2
mile at the surface. Some cams from the north Panhandle have shown
some improvement this evening but others, like Priest Lake look to
be fogging in. With Bonners Ferry and Sandpoint still reporting
1/4 mile visibility, will leave fog advisory and have night shift
see how conditions trend. May have to add Moses Lake area with
cams showing fog from Ephrata to Moses Lake to Othello but
generally stratus on the western reaches of the zone.

NAM, Gem, and GFS indicate a deepening stratus layer has it is
shoved east into the higher terrain resulting in spotty drizzle.
This has been added to the forecast and the good news is stratus
is less likely to allow temperatures to fall much in comparison to
fog. Last night, clear skies above a shallow fog deck allowed many
locations to cool below freezing but with stratus now in place, it
should be much more difficult to radiate more than 2-3 degrees
from current values. This will mean freezing temperatures will be
much more localized but could still present the opportunity for
slick roadways come the morning commute. As of 9pm...temperatures
from the West Plains to Davenport to Ritzville are hovering
between 33-34f so you can see how close the threat is.

Not the same story in the north Idaho Panhandle with temperatures
29-33f at locations like Bonners Ferry, Porthill, Sandpoint, and
Priest Lake. Expect a strong possibility for slick conditions by
Wed morning.

Overall, with the ridge weakening, the threat for fog will be
lower but low clouds will be likely. An upper-level cold front is
just crossing into northern Washington and has moved through the
northern Okanogan Valley and Methow Valley. Look for clearing
skies aloft behind this feature and light northerly push. I do not
think this will be enough to mix to the surface but cooling aloft
will weaken the strong inversions in place. /Sb

&&

Aviation...
06z tafs: the upper-level ridge will weaken this morning and
midlevel inversions will follow. Boundary layer winds have
switched to the SW and fog/stratus has been transported from the
basin...east into Spokane-cd'a and likely to move into Pullman.
Areas of dense fog are not as widespread as the last few nights.
This will be a short-lived pattern change with high pressure to
rebuild Wednesday evening and support the idea of fog developing
with any clearing Wednesday afternoon. Confidence lowers into Wed
afternoon regarding the extent of clearing and timing of fog
redeveloping. /Sb




&&

Preliminary point temps/pops...
Spokane 33 41 32 42 31 40 / 0 0 0 10 0 10
Coeur D'Alene 31 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 29 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...dense fog advisory until noon PST Wednesday for northern
Panhandle.

Washington...dense fog advisory until noon PST Wednesday for upper Columbia
Basin.

&&

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