Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 161147
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
347 AM PST Fri Nov 16 2018

.SYNOPSIS...
A cold front will drop through the region this morning and result
in a chance of rain and mountain snow showers this morning, with
drying from the north this afternoon. Temperatures will be cooler
today with locally breezy winds through north-south valleys.
The cool and dry weather will persist through the weekend into
early next week. The weather pattern may become more active as
Thanksgiving approaches.



&&

.DISCUSSION...
Today and this evening...An upper level trough will swing through
the forecast area today. Most of the moisture and precipitation
has been with the warm front and that is currently moving south
through the southern zones and should be out of the area by
sunrise. The cold front will follow this morning and will open
the door for scattered rain and snow showers through the morning,
and mainly in the up-sloping favored areas, but also expect a few
showers moving off the northern mountains through the early
morning hours. Drier air will move into the region this afternoon
behind the front and this will bring a drying trend to the area.
So, for today expect showers across the Cascades this morning
decreasing rapidly this afternoon. Showers will be a little slower
to dissipate across the Idaho Panhandle. Expect widespread
showers this morning, showers will continue from I-90 south to the
Camas Prairie and the Blue mountains through sunset with gradual
dissipation from north to south through the afternoon. Snow
accumulations will be mainly above 3500-4000 with additional
accumulations 1-3 inches possible. There may be some isolated
pockets of freezing rain for the Cascade valleys and the Okanogan
valley through sunrise. Accumulations will be light, by the
morning commute could be tricky in places. Temperatures will be
down 2-4 degrees over Thursday with highs only in the 40s. Winds
will be out of the north-northeast. These winds will get channeled
down the Okanogan valley and the Purcell Trench with gust 15-25
mph. The northerly winds will spill out onto the Waterville
Plateau and the Idaho Palouse as well with gusts 15-20 mph at
times.

Tonight through Saturday night...High pressure will creep into the
region tonight with the ridge axis between the coast and the
Cascades through Sunday. This will put the area in a dry and cool
northerly flow. Temperatures will continue to cool off a couple of
degrees each day. Winds will be light out of the northeast. The
forecast challenge then will be how much fog and stratus that will
form tonight and saturday night. Typically fog and stratus is
likely after light precipitation and building high pressure,
however, very dry air will move into the region through the day
and will likely mitigate any widespread fog/stratus tonight.
Saturday night there will be a better chance for fog and stratus,
especially for the northern valleys and the lower Columbia basin.
Tobin


Sunday through Thursday: Dry conditions continue early this week,
with some fog potential, before a precipitation threat develops
mid-week on. Through Tuesday the area remains under a ridge of
high pressure. Some middle to upper level clouds spill across the
region Sunday and then again toward Tuesday. Otherwise the first
part of the week will feature limited mixing, light winds and no
precipitation. However this will bring the threat of some late
night/morning fog and some air stagnation. Depending on how
persistent low clouds and fog are, temperatures may be held back
more than the current forecast. I attempted to show that potential
in the forecast.

Tuesday night to Thursday the ridge axis shifts east and a
trough moves onshore. Timing differences persist, with some model
solutions quicker to bring precipitation chances back in than
others. Most, however, keep the main threat in the Cascades
through Wednesday before expanding chances east Wednesday night
and Thursday. There is reasonable consistency/agreement to have
some high chance to low-end likely PoPs by late Wednesday into
Thursday near the Cascades crest. Some modest chances will also
be found toward Idaho by Thursday too. Thus some snow is possible
over the passes, which may impact Thanksgiving travel. What is
less certain is how much may fall, if any, as there is wider
disagreement in this respect. If there is a higher threat of
impacts it appears it would be for the Cascades passes. Some
solutions have only a couple inches (the most recent EC) and
others have several more inches (the most recent GFS). So stay
tuned. Overnight/morning temperatures would support the potential
for a rain/snow mix in some of the valleys and higher benches too,
but at this time precipitation here looks light. Model so suggest
some increase in winds going into the end of the week, so this
should help stir things up enough to trend temperatures upward
slightly by then. /Cote`

&&

.AVIATION...
12Z TAFs: The stratiform precipitation has moved out of the area
and the radar this morning is showing isolated to scattered
showers moving through the eastern portion of the forecast area.
Showers will continue through mid-morning then should be focused
over the Panhandle mountains south to the Blue mountains.
Mountain obscurations should be expected. Otherwise much drier
air is moving into the region as the flow turns northerly and
this will bring an end to showers for all of the TAF sites between
15z-18z. The northerly winds are piling up the boundary layer
moisture for KMWH/KEAT and expect MVFR vsby through 15-16z before
the drier air dissipates the fog. VFR conditons at all TAF site
before 18z. The drier air previously mentioned will inhibit
fog/stratus formation tonight. There may be some fog at KSFF
overnight but confidence is low. Northerly winds will have the
tendency to push any remaining boundary layer moisture up against
the Cascades and would effect KEAT. Guidance keeps KEAT VFR, but
this will need to be monitored the next 24 hours. Tobin



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        42  24  38  22  39  25 /   0   0   0   0   0   0
Coeur d`Alene  44  25  39  23  43  26 /  10   0   0   0   0   0
Pullman        45  25  42  24  44  27 /  30   0   0   0   0   0
Lewiston       49  30  46  27  48  29 /  40  10   0   0   0   0
Colville       43  27  40  22  39  25 /   0   0   0   0   0   0
Sandpoint      42  27  38  22  40  25 /  10   0   0   0   0   0
Kellogg        41  25  38  25  42  27 /  60   0   0   0   0   0
Moses Lake     49  24  43  19  41  21 /   0   0   0   0   0   0
Wenatchee      46  29  42  23  39  26 /  20   0   0   0   0   0
Omak           45  25  42  22  41  24 /  10   0   0   0   0   0

&&

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

&&

$$


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