Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 272329
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
429 PM PDT Mon Mar 27 2017

.SYNOPSIS...
Evening showers will taper off after sunset tonight. After a
short break in the weather tonight another round of widespread
moderate precipitation will arrive Tuesday night and last until
early Thursday. Friday will bring a dry break period before more
unsettled weather for next weekend.

&&

.DISCUSSION...
Tonight and Tuesday...A fairly quiet interregnum in the active and
wet weather pattern is enveloping the region. Afternoon scattered
showers concentrated mainly over the eastern basin and Idaho
Panhandle will minor out as the sun sets leading to a quiet and
largely clear overnight period...although some high thin cirrus
may wander in late tonight. Overnight low temperatures will be
chilly as the clearing conditions tonight allow radiational
cooling. Some pockets of early morning fog are possible in
protected valleys and near river beds. The moist boundary layer
and weak upslope winds over the eastern basin may promote some
morning low clouds by dawn Tuesday.

On Tuesday the next round of wet weather will take aim with
satellite indicating a deep Pacific moisture feed aiming at the
northwest coast this afternoon. Clouds will quickly increase and
thicken Tuesday morning...and light rain and high mountain snow
will probably begin over the northern zones by mid morning and
spread southward during the afternoon hours as a mid level warm
front develops and allows enhancement of the increasing moisture
feed. This will only be an initial shot of very light rain...only
a couple hundredths of an inch for most locations with the deep
basin remaining dry. /Fugazzi

Tuesday night through Wednesday night...Our next system is set to
impact the region with widespread precipitation during this
period. The warm front will continue to develop over the region
Tuesday night and Wednesday providing a broad area of isentropic
upglide. An atmospheric river will also be pointed into the region
providing PWATs of 0.7-0.9, or well into the 90th percentile.
This combination will lead to widespread rain across the area with
snow generally above 4-5k feet. By Wednesday night and into
Thursday morning, the best moisture fetch begins to sink to the
south and a cold front will sweep through the area. This will
focus the best chances for continuing precipitation over the
central Idaho Panhandle and far southeast Washington.

Precipitation totals thru Wednesday night look pretty healthy,
especially over far eastern Washington and the Idaho Panhandle. In
general, look for 0.3 to 0.6 across the eastern 1/4th of
Washington, 0.5 to 0.75 across the Idaho Panhandle valleys with
potentially over an inch of liquid in the mountains. The deep
Basin and Wenatchee area will probably see the lightest totals as
the isentropic lift looks weakest in this area. The immediate
Cascade crest will likely see liquid amounts in the 1 to 2 inch
range with some of that being tied up as snowfall in the higher
elevations.

Impacts: The additional rainfall will likely continue to aggravate
ongoing flooding issues. At this time, the hydrographs for main
stem rivers show some response, but don`t deviate much from their
general ongoing trends. Smaller streams and rivers, such as the
Little Spokane River at Dartford and Paradise Creek at Moscow,
will likely react with rises and low-land and lake flooding will
continue to be an issue. The other area of concern will be the
continued risk of mud and landslides in steeper terrain as the
soils are still very saturated, especially across far eastern
Washington and the Idaho Panhandle. /Kalin

Thursday through Monday: The active weather will wane a bit, although
more unsettled weather is still possible for the weekend and into
early next week. By the Thursday, the moist weather system exits
and precipitation tapers off as an upper trough moves into the
Pacific Northwest. This will bring cooler air aloft, more
instability and the chance for afternoon to evening convection
especially across southeast Washington and north Idaho for
Thursday. Showers should dissipate Thursday night as an upper
level ridge builds into the region. Low level moisture will linger
with light winds northerly winds which could lead to the
potential for patchy fog in the northern valleys late Thursday
nigh into Friday morning. Friday should be a dry day under high
pressure.

For the weekend and beyond, model differences persist in the timing
of the features while forecast confidence lowers. These issues
include the strength of this upper level ridge and the westerly
flow in the Pacific and what form it takes to break down the
ridge. The ECMWF is a bit more aggressive and faster solution,
bringing a strong Pacific jet and a more consolidated shortwave
into the region by Saturday, while the GFS and Canadian are slower
with a more amplified Pacific pattern and shows a trough digging
through the region on Sunday. It`s difficult to pin down any model
consensus. At this time, will trend to a climatology forecast and
a compromise of the solutions, keeping a mention of showers for
each day. Meanwhile, temperatures should be trending toward normal
for the start of April. /rfox

&&

.AVIATION...
00Z TAFs: Cold and conditionally unstable airmass over the
aviation area allowing surface based scattered showers with a few
isolated thunderstorms of the weak and short lived pulse variety
to linger a bit and diminish in intensity with loss of peak
heating and majority of it should be finished by 3Z Tuesday. Low
level southerly flow coupled with the leftover light moisture will
allow for some low level IFR stratus to form overnight and into
Tuesday morning. This stratus expected to break up/raise later
Tuesday morning. Next incoming weather system focuses a southwest
to northeast flow of moisture into the area tomorrow allowing for
clouds to invade the sky from the west and southwest and thicken
and lower as they do. Some light rain may occur during this
process Tuesday afternoon with ceilings and visibilities possibly
MVFR at times. /Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        35  49  40  51  40  52 /  20  40  70 100  60  40
Coeur d`Alene  35  46  37  49  39  51 /  30  50  70 100  80  50
Pullman        36  49  40  51  41  50 /  30  30  40 100  80  70
Lewiston       38  54  42  56  43  54 /  10  20  20  80  80  70
Colville       32  47  36  48  37  53 /  20  50  80 100  50  30
Sandpoint      33  45  34  47  35  50 /  20  60  70 100  80  40
Kellogg        33  44  35  46  37  46 /  40  50  50 100  90  80
Moses Lake     38  57  43  58  41  59 /   0  10  40 100  20  10
Wenatchee      37  53  39  54  38  58 /  10  10  60  90  20  10
Omak           35  50  39  52  37  58 /  10  20  70 100  20  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&

$$


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