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Area forecast discussion 
National Weather Service Spokane Washington
223 am PDT Wednesday Oct 7 2015

light rain will spread east across the region today as Pacific
moisture moves into the Pacific northwest. Drying is expected
Thursday and Thursday night as high pressure builds back into the
region. A big shift in the weather pattern will bring an
increasing risk for rain...mild temperatures...and windy
conditions late in the week and into the weekend as well.


today through Thursday night...model guidance is generally in good
agreement showing weak high pressure building into the region
through this portion of the forecast period. This would typically
result in a warm and dry forecast...but no so fat my friends.
Southerly flow will tap into deep moisture with origins all the
way down to the Hawaiian islands and associated somewhat with
hurricane oho. This will pump a great deal of moisture into the
region. Precipitable waters increase to between 1.00 and 1.25 inches today,
which is 250 percent of normal or greater. This is more than 3
Standard deviations above normal. With this much moisture to work
with it will not take much of a lifting mechanism to squeeze the
moisture out of the air mass. As the weak high pressure ridge
builds into the region a warm front will move north today and into
this evening. Weak isentropic up-Glide along the the 295-300k
surface will be enough to get wide spread precipitation mainly
today and early this evening. Then conditions dry out for Thursday
and Thursday night as the ridge strengthens and we lose the deep
fetch of moisture.

The forecast challenge will be the beginning time, length of
precipitation and the amounts. Looking at the sub-cloud layer for
the 00z sounding out lower atmosphere is extremely dry, imagine
that. So it will take some time to saturate the sub-cloud layer
for rain to actually hit the ground. This is where the models are
having a difficult time. The higher resolution models show light
rain as early as 14-15z, while the lower resolution models don't
saturate until closer to 18z if not later. This forecast leans
towards a compromise. As the ridge strengthens this evening the
already weak warm front falls apart and while there mill still be
plenty of moisture to work with the only lifting process then will
be up-sloping flow into the central Panhandle mountains. Rainfall
amounts will range from a tenth to a quarter inch of for the
Palouse with higher amounts up to a half inch in the local
mountains...a tenth of an inch or less for the Columbia Basin,
Spokane/Coeur D'Alene area, with lighter amounts up near the
Canadian border.

Cloud cover and rain will result in cooler temperatures today,
mainly in the 50s and 60s, before rebounding nicely Thursday with
clearing skies and warm air advection. Winds will be southwesterly
and generally under 10 mph. Tobin

Friday through Monday night: the main focus through this period will
be rain and winds. This has been a consistent message over the
last few days and confidence remain above average.

Overview: a deep area of low pressure reclaims the Gulf of Alaska
while a ridge of high pressure noses from the Pacific into California.
A strong southwesterly jet develops and draws tropical moisture
into the pac northwest. Meanwhile, shortwave energy periodically eject
from the offshore low ushering frontal boundaries into the region.
These boundaries will act to squeeze out light to moderate
rainfall...pending where they are and how long they reside. There
are two main shortwaves that will be the focus for precipitation.
The first impacts the inland northwest sometime during the
Saturday/Saturday night time-frame and a second Monday/Monday
night. There is also a weak front Friday night but precipitation
amounts look rather light with this feature.

The heaviest precipitation looks to fall along and west of the
Cascades with a second maximum in the eastern mountains including
the Idaho Panhandle and far northeastern Washington. In between,
precipitation is definitely a possibility but amounts are less
certain. Locations within the Cascade rain shadow will pick up
very little precipitation.

Rain amounts: 1-3 inches of rain will be possible along the immediate
Cascade crest. 0.50 - 1.50 inches of rain in the eastern mountains
within the Idaho Panhandle and NE Washington. 0.20 -0.50" for the rising
terrain of ern Washington but I could see amounts upwards of an inch
where rain is a bit more persistent. For the Hwy 97 corridor
from the Okanogan Valley to Wenatchee area...amounts will generally be
under 0... we will need to closely monitor the potential for
stalled or slower moving frontal boundaries given the tropical moisture
entrained into the jet stream.

Wind: there is a strong potential for windy conditions given the pattern.
At this time, the windiest periods look to be late Saturday
afternoon into early Sunday with another push Monday into Monday
night. The potential for sustained winds between 15-30 mph coupled
with gusts 30-50 mph does exist. Higher gusts in excess of 50 mph
will be likely on the highest ridgetops such as Mission Ridge and
schweitzer mtn.

Temperatures: Friday and Saturday will be quite mild for October with
70s and lower 80s Friday giving way to 70s on Saturday. The air mass
will cool Sunday and Monday with afternoon highs cooling back into
the 60s.

Impacts: the potential for wind impacts is moderate but exact speeds
carry some uncertainty. If the strongest winds come through
overnight, there may be a lower potential for strong wind gusts.
We cannot completely rule out blowing dust but this carries lower
confidence. As for precipitation, any moderate to local heavy rain
will be a problem for burn scars. This is not your typical
"thunderstorm" variety rain but will have tropical connections and
that does raise some concern. The Wolverine, kaniksu, grizzly, and
any additional burn scars in the Idaho Panhandle look to carry the
highest threat for rainfall amounts in excess of half an inch but
we are far from certain that this will fall quick enough to lead
to problems. This is a good time to just be aware and keep close
tabs on the forecast. /Sb

Tuesday and wednesday: drier conditions return to the region under
westerly flow. Look for near temperatures to remain a few degrees
above normal and fair conditions. /Sb


06z tafs: expect thicking mid and high clouds tonight as a warm
front approaches. Areas of light rain will increase on Wednesday
as the warm front tracks across the region. Models currently show
light rain over southeast Washington including kpuw in the morning
lifting north for the remainder of the taf sites by afternoon.
Areas of MVFR ceilings are expected as light rain develops...including
kpuw/kgeg/ksff/kcoe. Moist upslope flow into kgeg could result in
IFR conditions Wednesday evening but confidence in this is low. Jw


Preliminary point temps/pops...
Spokane 60 50 70 52 75 53 / 60 50 10 0 10 20
Coeur D'Alene 60 49 69 50 76 51 / 60 60 10 10 10 20
Pullman 59 52 73 52 80 50 / 90 60 10 0 10 10
Lewiston 64 52 77 54 85 53 / 60 50 10 0 10 10
Colville 63 48 68 47 72 48 / 50 30 10 10 10 30
Sandpoint 60 50 66 46 72 47 / 50 40 20 10 10 20
Kellogg 57 49 67 49 76 49 / 70 70 20 10 10 10
Moses Lake 64 53 74 50 78 53 / 60 10 10 0 10 20
Wenatchee 64 54 73 55 77 56 / 60 30 10 10 10 30
Omak 64 53 71 53 73 53 / 50 30 10 10 20 20


Otx watches/warnings/advisories...


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