Area Forecast Discussion
Issued by NWS Spokane, WA

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378
FXUS66 KOTX 170042
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
542 PM PDT Mon Oct 16 2017

.SYNOPSIS...
A wetter and windier weather pattern is expected starting Tuesday.
Unsettled weather will continue Wednesday and Thursday however
with relatively mild temperatures for the season. A cold front
late in the week will cool the region down again to more seasonal
temperatures with the return of mountain snow.


&&

.DISCUSSION...

...Windy tomorrow afternoon and evening...

Tonight through Wednesday night: Jet stream remains within very
close proximity to the north, if not directly overhead, at
times over Eastern Washington and Northern Idaho as an upper level
flat ridge of high pressure remains in place for most of this time
interval. As such disturbances moving through the flow have
potential to bump some of the jet steams upper level winds down to
the surface with their passage. Such passages are expected to occur
Tuesday afternoon and evening and to a lesser degree Wednesday
afternoon and evening. A wind advisory was issued earlier and later
expanded to address the Tuesday afternoon and evening winds.  This
jet stream positioning will favor snow levels high enough to limit
any snowfall to the higher mountain terrain generally near or above
5000 feet MSL. Cooling trend in temperatures through this interval
will allow daytime highs to run closer to seasonal average values
while overnight lows will be slightly on the warmer side given the
suggested mixing and cloud cover inhibiting overnight radiational
cooling this jet positioning should be able to provide. Similar
reasoning suggests a significant rain shadow to the east of the
Cascade Crest should keep much of the Columbia Basin and good amount
of lowlands from receiving anything other than extremely light
rainfall. The usual exceptions to this will be portions of
Northeast Washington and the North Idaho Panhandle where the terrain
allows the incoming disturbance to run upslope, so pops and qpf
there area higher Tuesday and even higher still on Wednesday.
/Pelatti

Thursday through Monday...
Beginning Thursday, the upper trof that is the cause for the
active weather will finally approach the PacNW coast. As it
approaches, the Inland Northwest will again be in the warm sector
so temperatures will rebound into the upper 50s to lower 60s while
snow levels increase to over 7000 feet. The cold front associated
with the trof will bring another round of wind and rain to the
region and drop snow levels substantially by Friday night. One of
the changes made to the forecast was to increase the chance of
precipitation and rain amounts with this frontal passage. Thursday
is looking like it will be a very wet day except for the lee of
the Cascades that should down slope. Precipitation will last
through much of Thursday night into Friday morning before finally
drying out. Again, this is quite the change from previous model
solutions that had much less rain through this 24 hour period.

Winds during this time will remain breezy but nothing like the
Tuesday event. As the trof moves overhead Friday, there is
potential for another breezy day in addition to plenty of
convection. Snow levels will be down to 3000-4500 feet across the
region so scattered valley rain and mountain snow showers are
likely Friday afternoon.

That doesn`t last long as the next wave kicks the trof to the
east and another plume of moisture streams out ahead. This is
another change to the forecast; adding higher chances for rain
Saturday through Saturday night again with breezy winds. It`s not
until Sunday night and Monday where the models are finally drying
out the region under a building ridge of high pressure. Long range
models are indicating that this could be the beginning of a
period with above average temperatures and dry conditions. Some
models show snow levels above 11000 feet by mid next week!/AB

&&

.AVIATION...

...STRONG WINDS TUESDAY AFTERNOON AND EARLY EVENING...

00Z TAFS: A robust cold front will bring strong winds to the
aviation area Tuesday. A low-level jet develops ahead of the
front creating low-level wind shear roughly 15-18z then expect
sustained winds 20-30 mph accompanied by gusts 35-50 mph.
Isolated gusts between 22-00z may approach 50-60 mph at times
with the passage of the main cold front. There is some uncertainty
regarding when Lewiston transitions to westerly flow between
19-22Z. Winds may lead to areas of blowing dust and haze with
forecast favoring haze. Otherwise, the front to bring ceilings
arnd 6-8k ft AGL and brief pcpn to the terminals. /sb


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        43  59  41  59  47  59 /   0  60  20  50  50  70
Coeur d`Alene  42  60  39  59  45  60 /   0  70  20  60  50  70
Pullman        43  63  44  64  48  64 /   0  50  50  40  30  40
Lewiston       46  70  48  71  50  71 /   0  10  20  30  20  10
Colville       38  58  35  55  42  57 /  10  50  20  50  60  70
Sandpoint      36  55  34  54  41  56 /  10  80  30  60  70  80
Kellogg        40  58  39  55  43  59 /   0  60  60  60  50  50
Moses Lake     39  65  39  65  45  63 /   0  10  10  30  30  40
Wenatchee      45  62  40  61  47  59 /   0  20  10  30  40  40
Omak           40  63  34  60  42  59 /  10  20  10  40  60  70

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from 1 PM to 8 PM PDT Tuesday for Central
     Panhandle Mountains-Northern Panhandle.

     Wind Advisory from 1 PM to 8 PM PDT Tuesday for Coeur d`Alene
     Area-Idaho Palouse.

WA...Wind Advisory from 1 PM to 8 PM PDT Tuesday for East Slopes
     Northern Cascades-Northeast Mountains-Okanogan Highlands-
     Okanogan Valley-Wenatchee Area.

     Wind Advisory from 1 PM to 8 PM PDT Tuesday for Lower Garfield
     and Asotin Counties-Moses Lake Area-Spokane Area-Upper
     Columbia Basin-Washington Palouse-Waterville Plateau.


&&

$$



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