Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 242327

Area Forecast Discussion
National Weather Service Spokane WA
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 WA Coast will
usher in the next round of precipitation for the Inland NW
tonight. As of 2PM...the front and meridional band of rain was
located on the WA 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
WA and N Idaho overnight through sunrise. The system will tap into
decent moisture with PWATS 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 WA 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 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 WA and ID and then
bring it south across SE WA and the southern ID 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, N ID 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
ID 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 SE winds
remain in place across the southeast but incoming guidance is not
as strong so opted to remove LLWS. Lewiston and Pullman will still
have veering wind profile from SE 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


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



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