Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 281346
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
546 AM PST SAT FEB 28 2015

.SYNOPSIS...
Breezy to windy conditions will bring cold wind chill
temperatures this morning. Otherwise dry weather is expected
through Sunday. Another weather system will pass Monday into early
Tuesday with wintry weather possible, especially for the Idaho
Panhandle. Much colder air will move into the area behind this
system with temperatures well below average for the middle of next
week. A dry period, with moderating temperature will follow for the
end of next week.



&&

.DISCUSSION...
For Today...Updated...

The upper low that moderate precipitation to the central and
southern Cascades on Friday has now dropped into the south central
Oregon...meanwhile high pressure will try to nose into BC today.
This will put the Inland Northwest in a dry northeasterly flow. As
such expect plenty of sunshine...cooler temperatures and breezy to
windy conditions for today.

The surface gradient is less than guidance had suggested for
early this morning and is already beginning to weaken. In addition
clear skies did indeed result in a low level inversion and
resulted in some decoupling of the winds. This kept the stronger
mid level winds from surfacing for most of the forecast area early
this morning. With ample sunshine today the atmosphere should
destabilize and allow the 25-30kt winds at roughly 5000 feet to
mix to the surface. This will allow winds to increase after
sunrise with sustained northeast winds 15-25 mph and gusts around
30 mph through late morning. The strongest winds are still
expected down the Purcell trench and the Okanogan valley but
should remain below advisory criteria and the wind advisory was
cancelled. By this afternoon the surface gradient weakens further
and winds will decrease. Temperatures will cool 5-6 degrees
across the eastern zones and 1-3 degrees across the western zones.

Tonight and Sunday...A dry northerly flow will keep the weather
quiet if not on the cool side of normal with clear skies. Light
winds and clear skies will allow strong radiational cooling for a
chilly morning on Sunday and the chance for local fog near water
sources.

By Sunday night the region will begin to feel the effects of the
next upper level low that will drop out of British Columbia. The
models are still showing quite a bit of difference on timing and
placement of the upper low, and interestingly all are showing
pretty good run to run consistency. So confidence in the forecast
for this period is only low to moderate at this time. As the low
drops south there should be enough over water trajectory to tap
into a little Pacific moisture. This will result in the chance for
some light snow for the north Cascades, but only very light
accumulations. The remainder of the forecast area will see
increasing high level clouds. The sky cover will be enough to
inhibit the good radiational cooling with temperatures a few
degrees warmer than Sunday morning. Tobin

Monday through Tuesday night...An upper trough will slide south
through British Columbia, bringing a chance of precipitation to
the region. There are model differences in the track of the best
forcing with the ECMWF wetter across eastern WA. The GFS shows
more of a glancing blow across the northern panhandle. The NAM is
in between with a decent amount of precip for the Idaho panhandle
but little for E WA. The north-northwest trajectory will place the
highest confidence of measurable precip in the mountains of
northeast WA and the Idaho panhandle with lower confidence for
central WA and the east slopes of the Cascades. Snow levels will
be at most valley floors but this overland track will not bring a
lot of QPF with it. The Idaho panhandle will likely see some
accumulating snow and passes will be affected but this is not
expected to be a big snowmaker since it will move through the
region quickly. Northerly winds will once again increase down the
northern valleys as the surface pressure gradient strengthens
Monday night. The northerly trajectory will favor the Okanogan
Valley and south into the Waterville Plateau more than the Purcell
Trench with this system. For now this is not looking strong enough
for a wind advisory. The elevated winds will keep overnight temps
from falling off a cliff. By Tuesday night the gradient slackens
and winds will diminish. Clearing skies and light winds will allow
temperatures to plummet overnight with some of the more sheltered
valleys dropping into single digits.

Wednesday through Friday...The ridge of high pressure will rebound
over the region with mainly dry conditions for the Inland
Northwest. Synoptic flow will shift from northerly to more
northwesterly and then westerly with daytime temperatures
moderating through the week. Overnight lows will still be on the
cool side as clear skies and light winds allow efficient
radiational cooling. Late in the week some moisture starts to ride
along the ridge with the threat of precipitation along the
northern border. /Kelch


&&

.AVIATION...
12Z TAFS: Some high clouds will linger along the southern border
with Oregon through mid morning...otherwise sunny today and clear
and chilly tonight. VFR conditions can be expected at all TAF
sites through 12z Sunday. Winds will become gusty and locally
strong with a general north to northeast winds of 10 to 20kts
with gusts 20 to 25kts at all TAF sites except KLWS. Tobin



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        41  19  42  25  39  21 /   0   0   0   0  30  20
Coeur d`Alene  41  17  44  23  40  18 /   0   0   0   0  50  50
Pullman        41  20  42  27  40  21 /   0   0   0   0  40  30
Lewiston       45  24  45  29  44  25 /   0   0   0   0  30  20
Colville       45  21  47  26  43  22 /   0   0   0  10  20  20
Sandpoint      39  17  41  22  38  17 /   0   0   0  10  60  50
Kellogg        37  18  41  24  37  16 /   0   0   0   0  70  70
Moses Lake     49  23  48  28  48  25 /   0   0   0   0  20  10
Wenatchee      49  28  49  32  48  25 /   0   0   0  10  20  10
Omak           48  24  49  28  46  23 /   0   0   0  10  20  10

&&

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

$$



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