Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 061137

Area Forecast Discussion
National Weather Service Spokane WA
436 AM PDT TUE OCT 6 2015

High pressure will deliver dry conditions and light winds Today.
This ridge of high pressure weakens mid week with a chance of
light rain entering the region. A big shift in the weather pattern
will bring an increasing risk for rain...mild temperatures...and
windy conditions late week and into the weekend.



Today through Wed Nt: The upper ridging which helped to bring dry
wx the last couple days will weaken over the region ahead of an
approaching maritime frontal system currently off the Pac Nw
coast. Our first threat of rain will be Wed, with this threat not
ending until Thurs. Forced by moderate moist isentropic ascent
over a warmfront, this rain should be fairly light and amount to
no more than a tenth of an inch for most towns. The main change we
made to the fcst was to increase pcpn amnts a bit for SE Wa and
the Cntrl Idaho Panhandle Wed and Wed Nt. By late Wed Nt, this
front will have moved far enough north to end the pcpn threat for
a large part of the Columbia

Thursday through Friday morning:  A warm front will continue to lift
north out of the region and high pressure will briefly restrengthen.
Look for lingering clouds and light rain to lift north through
NE WA and the Idaho Panhandle by late afternoon and majority of
the region experiencing dry and mild conditions.

Friday afternoon through Tuesday: Weather models continue to show an
active weather pattern for the upcoming weekend...continuing into
Monday before things calm down around Tuesday. This has been a
consistent message over the last few days and confidence continues
to grow. Confidence is highest for above normal warmth (Fri/Sat),
rain along the Cascade Crest and Northern Mountains, and gusty
winds. Uncertainty exists for rain chances away from these
locations, amounts in any given location, and strength of wind

* Overview: The large scale weather pattern over the Northern
 Pacific will undergo some major changes as low pressure becomes
 re- established over the Gulf of Alaska. A strengthening
 southwesterly jet on its southern and eastern flank will draw
 subtropical moisture toward the Pac NW. Initially, the jet is
 aimed into southwestern British Columbia Friday but shortwave
 energy ejecting from the low will waver the jet southward at
 times and allow frontal systems to pass through the region. This
 will be a very anomalously rich moisture plume which will contain
 the remnants of Tropical Storm 07C (Oho) currently south of the
 Hawaiian Islands. I anticipate this tropical moisture will also
 play havoc with weather models for the next few days regarding
 the finer details but all data suggest PWATS to surge near to
 over an inch by the weekend. To put this into perspective: The
 PWAT output on the NAEFS (North American Ensemble Forecast
 System) has never been observed in the CFSR climatology for a
 3-week period centered around October 10th. The period of record
 is from 1979-2009.

* Rain: A steady and potentially moderate rain is setting up for
  the Cascade Crest and northern mountains. Pending the strength
  of each frontal system, rain chances will waver north and south
  however it does look promising for a Cascade rain shadow so
  forecast will go with lower chances along Hwy 97 and western
  Columbia Basin, highest northern mountains, and carry the lowest
  confidence south of Spokane to Kellogg. Saturday night and
  Sunday look to be the best chance for rain outside the mountains
  with the passage of a cold front. Moderate rainfall amounts will
  be possible but carry high uncertainty.

* Wind: Saturday and Sunday stand out as the windiest days right
 now. Per latest GFS, there is a potential for sustained winds
 between 15-30 mph with gusts toward 30-45 mph and higher gusts in
 the mountains. This will be a more typical wind direction that
 blows from southwest to northeast.

* Temperatures: Friday and Saturday will be the warmest days with
 70s common in most locations. Some areas of southeastern WA and
 the lower ID Panhandle stand a decent shot of 80s. The air mass
 will cool Sunday and Monday but only knock temperatures back into
 the 60s...still a handful of degrees above October standards.

* Impacts: Details are far from certain to hone in on exact
 impacts but pattern recognition suggest the potential for wind
 impacts and maybe excessive rain with the idea of moisture from a
 tropical storm coming through. Given how the summer has gone,
 blowing dust cannot be ruled out either. /sb


12Z TAFS: VFR wx conditions are expected...with high cloud
ceilings of 25k-30k ft agl. Gusty winds are not expected and
should remain light and diurnally/terrain driven.


Spokane        72  49  68  51  71  52 /   0   0  10  20  20  10
Coeur d`Alene  72  46  68  48  71  50 /   0   0  10  20  20  10
Pullman        74  46  68  51  74  51 /   0   0  10  30  10  10
Lewiston       77  52  73  55  78  55 /   0   0  20  30  10  10
Colville       76  45  69  47  69  47 /   0  10  10  20  20  10
Sandpoint      69  41  66  43  67  46 /   0  10  10  20  20  10
Kellogg        72  45  65  45  68  49 /   0   0  10  30  20  10
Moses Lake     76  47  73  52  76  51 /   0  10  10  20  10  10
Wenatchee      76  55  74  56  75  56 /   0  10  20  20  10  10
Omak           74  51  74  53  73  53 /   0  10  10  20  20  10



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