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fxus66 kotx 151002 
afdotx

Area forecast discussion
National Weather Service Spokane Washington
302 am PDT sun Sep 15 2019

Synopsis...
a cool, wet frontal system will stall over western Washington on
Sunday and bring soaking rains to the Cascade mountains. The front
eventually pushes across the region by Monday morning. Showery,
breezy and cool weather will persist across the inland northwest
into the middle of next week. Drier and more seasonal weather is
possible late next week.

&&

Discussion...
today through Monday night: a deep upper low is dropping southeast
along the British Columbia coastline near Vancouver Island early
this morning. A cold front associated with this large feature is
bringing widespread rain to western Washington and the Cascades. As the
main energy with this low dives southward, it will undercut the
inland northwest. The front will lose its punch as flow aloft
becomes parallel to the boundary. The result will be rain slowly
spreading east but then breaking up into light rain showers. It's
not until later Sunday night and early Monday morning that the
front gets a kick from another vort Max rotating around the base
of the low. This will push the frontal boundary through eastern
Washington and northern Idaho resulting in a period of light rain
Monday morning. Showers will finally diminish in coverage before
the next round invades Tuesday.

A few details that are Worth pointing out over the next 24 hours
include an impressive temperature gradient from southeast to
northwest today. While Lewiston will remain dry and in the sun,
their temperatures will reach the low 80s. Meanwhile under the
thick clouds and periods of rain, Omak will be lucky to get into
the lower 60s. This sharp thermal and pressure gradient will yield
increasing winds along and ahead of the frontal boundary. Winds
from the lc valley to the Palouse and over to the lower Columbia
Basin will be warm and gusty.

With rainfall totals not overly impressive and winds well below
advisory threshold, the expectation is that this frontal boundary
is a very low impact event. /Ab

Tuesday through thursday: a secondary upper level low will drop
out of the Gulf of Alaska on Tuesday, and very slowly tracking
through the region into Wednesday and possibly Thursday. Periods
of showers are a good bet across most of the region Tuesday
through Wednesday. Breezy southwest winds also appear likely on
Tuesday as the initial front passes through. The upper low drops
south toward California/Nevada on Thursday, but with cyclonic flow remaining
over the region, a few showers will continue to be possible. Look
for high temperatures in the 60s across the region during this
timeframe, which is on the order of 5 to 15 degrees cooler than
normal for this time of year.

Friday through sunday: northwest flow aloft will dominate over
the region on Friday as high pressure amplifies over the eastern
Pacific. A few showers will continue to be possible, particularly
across the eastern half of the County Warning Area. The ridge of high pressure
will eventually build into across the western US late next week
and bring warmer and drier weather, but the timing remains
uncertain.
Dang

&&

Aviation...
06z tafs: a low pressure trough will dig off of western
Washington. There is a good tap of moisture in the warm sector
with the cold front just making its way into Vancouver Island.
The moisture tap will become more meridional with time as the
trough digs. This will result in clearing across southeastern
Washington and into the Idaho Panhandle tonight. Thick mid to high
level clouds will remain over the Cascades and into the Okanogan
Highlands with light rain possible at times. Rain will eventually
make its way into keat Sunday morning. There is low confidence for
IFR/MVFR conditions at keat with the rain -- this will be
dependent on how much rain occurs. Westerly winds will increase
Sunday afternoon across the basin with gusts to around 20 kts
possible. /Svh




&&

Preliminary point temps/pops...
Spokane 74 49 62 44 63 47 / 0 10 40 20 30 70
Coeur D'Alene 76 48 62 44 62 46 / 0 10 40 30 30 50
Pullman 77 45 61 41 64 44 / 0 10 40 30 30 50
Lewiston 83 54 68 50 71 53 / 0 10 40 40 20 50
Colville 73 42 67 37 65 40 / 40 40 50 30 40 70
Sandpoint 74 47 62 43 60 45 / 10 10 30 40 30 60
Kellogg 76 50 64 47 61 49 / 0 10 20 40 30 50
Moses Lake 72 49 69 43 66 45 / 20 40 10 0 50 70
Wenatchee 65 53 68 50 63 51 / 70 40 10 0 70 80
Omak 64 50 67 45 63 49 / 80 40 30 10 60 60

&&

Otx watches/warnings/advisories...
Idaho...none.

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