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000
FXUS66 KOTX 091218
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
415 AM PST Mon Dec 9 2013

.SYNOPSIS...
Periods of light snow will bring portions of the Idaho Panhandle an
inch or two of snow today and tomorrow. Look for temperatures to
inch upward this week. By Thursday, readings will be close to
average. The arrival of a frontal system Thursday night and Friday
will bring a good chance of wintry precipitation to the region.


&&

.DISCUSSION...

Today through Tuesday: Weak warm air advection combined with an
subtle influx of mid-level moisture will bring periods of snow to
the Idaho Panhandle and extreme eastern Washington today, tonight
and tomorrow. An Alberta Clipper currently near Calgary (as of
2AM) will slide into North Dakota by this afternoon. The passage
of this disturbance through Montana today will enhance mid-level
warm advection today, especially this morning. The moisture
advection for precipitation today will actually be coming at us
from the northwest which is not the most direct way to bring
moisture into the region. However, given the arctic air in place,
it does not take much to generate precipitation. Similar to
yesterday, there will be a deep layer of moisture within the snow-
growth layer (-10C to -20C). A favorable moisture profile coupled
with the cold temperatures should yield high snow ratios. Using
precipitation values from the SREF produce snow amounts of 1-2
inches from Wallace southward to Dear, St Maries, Clarkia and
Winchester. It looks like the majority of the accumulation will
occur prior to noon with the strongest warm advection and deepest
moisture.

Another round of light snow for the southern Idaho Panhandle
appears likely late tonight into Tuesday morning. This round of
mid-level warm advection is associated with a more subtle upper
level wave in the northwest flow. The introduction of more low
level moisture into the atmosphere courtesy of precipitation will
probably mean a good chance of stratus over the Palouse which may
creep west and north Tuesday night into Wednesday. The pattern
which produced a good deal of sunshine over the last several days
will likely give way to more cloudiness this week. /GKoch

Wednesday through Friday night....Models agree with the pattern
change placing the synoptic scale ridge of high pressure axis over
Eastern Washington Wednesday with the Gulf of Alaska low and its
associated wet frontal zone digging into the west side of it.
Models diverge a bit on ridge deamplification and the start of
snow with ECMWF being roughly 12 hrs faster which I feel is the
favored model. Moisture overtops the ridge and overruns the cold
air in place at lower levels and snow enters in west to east
trajectory, not as robust and clean as earlier depicted, thus
pops have been decreased somewhat Wednesday thru early Thursday.
By late Thursday the ridge is pretty much flattened and replaced
with the zonal flow allowing the wet frontal zone to continue to
glide over the cold air in the area at low levels. Thus Snow
remains precipitation of choice. This warm southerly flow may
produce a crossover temperature above +3 C above the cold air at
the surface so freezing rain and ice pellets will continue to be
mentioned for late Thursday and Thursday night in southern parts
of the Basin. Friday the trof exits but the pattern remains
cluttered with moisture and energy fluxing through the northwest
flow over the area, too cluttered in fact to significantly reduce
pops. Forecast temps along with snow levels show a general rising
trend through this interval. /Pelatti

Saturday and Sunday: A moist West, Northwest upper level pattern
will impact the region for this period. This pattern is expected
to bring snow to the mountains in the region with the heaviest
amounts in the Cascades. The lower level wind pattern is a West,
Southwesterly pattern. This will allow for warmer temperatures to
creep into the region and rebound to around the seasonal normals.
With cloud cover acting as insulation, nighttime temperatures are
expected to be at or around freezing in the valley locations.
Precipitation in the valleys will be mostly rain during days with
a slight chance of snow at night. /JDC

&&

.AVIATION...
12Z TAFS: Bands of light snow are expected over the next 24-36 hours
over the Idaho Panhandle and extreme eastern Washington. The most
significant activity will likely occur between 12z-18z today and
again between 09z-15z Tuesday morning. Runway accumulations should
be less than a half inch at Spokane, Coeur D`Alene, Sandpoint, and
Lewiston. The Kellogg area may receive a bit more snow, an inch or
more. In general, the snow that falls today and tonight will be dry
and fluffy, not the kind of snow that sticks to the pavement well.
Cloud heights may temporarily fall below 3000 feet this morning over
the Idaho Panhandle and in the Spokane area. /GKoch


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        19  13  24  15  28  22 /  50  20  30  10  30  20
Coeur d`Alene  18  15  25  16  29  22 /  80  50  50  20  30  30
Pullman        20  12  27  19  31  24 /  40  40  50  30  30  20
Lewiston       23  17  30  23  35  26 /  20  30  40  20  20  10
Colville       20  13  25  13  28  19 /  40  30  20  10  40  30
Sandpoint      18  13  23  14  27  19 /  70  60  40  20  40  30
Kellogg        17  14  24  18  29  23 /  90  80  80  50  40  30
Moses Lake     20  10  27  16  30  22 /  10  10  10  10  10  10
Wenatchee      19  14  27  19  31  24 /  10  10  10   0  20  10
Omak           20  12  25  16  28  21 /  10  10  10  10  40  30

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&

$$