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Area forecast discussion 
National Weather Service Spokane Washington
427 PM PDT Mon Oct 24 2016

a cold front brings light rain and High Mountain snow this
evening and tonight. A few showers will linger in the mountains
Tuesday then a wetter more widespread rain event arrives
Wednesday, with the potential for moderate to locally heavy
rainfall across the east slopes of the northern Cascades.
Occasional wet weather will then continue at times through the end
of the week.


tonight through Tuesday night: a cool occluded frontal boundary
extended from a 970mb low pressure system off the Washington coast will
usher in the next round of precipitation for the inland northwest
tonight. As of 2pm...the front and meridional band of rain was
located on the Washington coast and will begin to make its charge eastward
tonight as the shortwave off the California coast swings north and

Rain will begin to spread into the Cascades around 5pm this
afternoon and slowly work its way across the remainder of eastern
Washington and north Idaho overnight through sunrise. The system will tap into
decent moisture with precipitable waters around 0.70" but dry subcloud layers
and short duration of the precipitation event will only yield
between a 0.15-0.35" for most mountain locations and lower amounts
in the deep Basin. A few spots in the northern and eastern
mountains could see amounts closer to half an inch but this
should be more isolated in nature. As such, little to no impacts
are expected.

Drier air will work into the basin Tuesday morning and afternoon
allowing ample sunshine and temperatures into the upper 50s to
lower 60s. This warming will help destabilize the atmosphere
and renewing the threat for isolated light showers across the
mountains. Instability parameters are not very impressive so
thinking precipitation amounts associated with this activity will
be very light and under a tenth of an inch.

The next system approaches from the south Tuesday night with light
rain and sprinkles expanding into far southern Washington and north-
central Idaho just prior to sunrise. /Sb

Wednesday and Wednesday night: the longwave trough off the coast
remains off shore leaving the region under southwest steering flow
which will advect a plume of very moist air over the region. Pwats
are near one inch over most of the region and well above an inch
for central Washington. A warm front will provide the main lift
for this rain event, moving up from the south as a weak ridge
briefly builds to our east. Strong associated isentropic lift will
bring widespread rain through the day Wednesday, with upslope flow
into the east Cascades bringing over an inch of rain to the
Cascade crest, though everyone will get rain. Precip tapers off to
the south late Wednesday before a slow moving occluded front moves
through from the west late Wednesday or early Thursday. Confidence
on timing of this is low to moderate at the moment. This is a
fairly warm system and snow levels will remain high, generally
above 6,000 ft, and rising through the day Wednesday. /Bwilliams

Thursday and Thursday night: models agree that a cold front will
move through the area Thursday. However the GFS is quite a bit
faster in its timing than the European model (ecmwf) or NAM. For now have trended
the forecast towards the slower ec/NAM timing, but will continue
to need to be monitored. Kept the best chance of morning
precipitation across the northern portion of Washington and Idaho and then
bring it south across southeast Washington and the southern Idaho Panhandle in the
afternoon. This is a quick moving system so precipitation amounts
will be fairly light compared to previous systems this
month...ranging from a few hundredths in the Columbia Basin to
0.10-0.25 for the Palouse/Spokane/Coe regions to 0.30-0.50 for NE
WA, north Idaho and the Cascade crest. Some mountains will likely receive
locally higher amounts. The front quickly exits the region
Thursday evening with just some lingering rain showers across the
Idaho Panhandle. Conditions will dry out overnight. Have added some
patchy fog from Spokane north and east across the valleys during
the overnight hours and into early Friday morning.

Friday through monday: the Pacific northwest will remain in a
moist southwest flow through the weekend as a trough remains off
shore through Sunday and a weak ridge hangs around The Rockies.
This will keep rain in the forecast everyday...though the better
chance of rain will be in the mountains. There is the possibility
of a cold front moving through Sunday night or Monday. Cooled
temperatures a few degrees for this period, but daytime
temperatures will remain at or a few degrees above average for
this time of the year and overnight lows will be about 6-10
degrees above average. /Nisbet


00z tafs: frontal occlusion carrying light rain currently extends
from Seattle to Portland will begin a slow progression to the east
overnight. Showers or periods of rain likely for most terminals
but amounts look light and forecast backed off on low ceilings
thinking brief MVFR cigs near to end of pcpn. Gusty southeast winds
remain in place across the southeast but incoming guidance is not
as strong so opted to remove low level wind shear. Lewiston and Pullman will still
have veering wind profile from southeast to SW until front moves through
early morning. Confidence declines after 12z how far south the
front will sag south of Pullman-Lewiston or stall over these
areas. All other terminals to experience VFR skies and occasional
wind gusts across the basin to 15 mph. /Sb


Preliminary point temps/pops...
Spokane 45 56 45 50 47 55 / 100 20 10 100 70 60
Coeur D'Alene 46 56 44 49 47 55 / 100 40 10 100 70 70
Pullman 46 57 46 55 48 57 / 90 50 30 90 30 60
Lewiston 49 63 49 60 50 61 / 70 60 30 70 20 60
Colville 43 55 40 46 45 53 / 100 30 10 100 90 60
Sandpoint 43 53 40 47 44 52 / 100 60 10 100 80 70
Kellogg 43 52 42 48 45 54 / 100 70 20 100 50 70
Moses Lake 42 61 46 54 47 58 / 70 10 20 100 70 40
Wenatchee 44 60 44 49 46 57 / 100 10 20 100 80 40
Omak 45 58 41 47 46 55 / 100 20 10 100 90 50


Otx watches/warnings/advisories...


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