Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 211130
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
430 AM PDT SUN SEP 21 2014

.SYNOPSIS...
Strong high pressure will provide a generally clear...warm and
dry rest of the weekend for the Inland Northwest. The new work
week will start out with continued above normal temperatures...but
a weak cold front will bring a chance of showers starting Monday
night. From mid-week onward an approaching deep trough will
increase the probability of rain with cooler temperatures.

&&

.DISCUSSION...
Today through Monday: A ridge of high pressure will keep the
weather over the Inland Northwest unseasonably warm and dry.
Temperatures running about 2 to 5 degrees warmer than yesterday,
making it the warmest day of the week. North and east winds will
become lighter by afternoon and evening. By tonight, the upper
ridge axis shifts east and allows a stream of high level moisture
to creep northward from Oregon. This moisture should reach the
Cascades by Monday morning as a weak shortwave ripples through the
flow. This will be the start of the upper ridge breakdown. Expect
a slight chance of showers to develop over the Cascades Monday
morning as the moisture profile deepen and then the chance of
showers shifts across the northern mountains through the day and
evening. Instability looks to be capped so will keep mainly
showers in across the area. The exception would be across
southeast Washington into the central Idaho panhandle where there
could be the potential of lightning. It will continue to be mild
with the low level thermal ridge lying over the area. Low level
winds will shift to southwesterly by Monday afternoon as the
shortwave passes. /rfox.

Mon Nt through Thur Nt: With a weak wave still over the area Mon
Nt, we kept a small chance of rain showers for mainly the Idaho
Panhandle. Confidence is low that this short- wave will be an
efficient pcpn producer, but model guidance does show a decent
signal for the possibility of high- based convective pcpn Tues
morning. The ECMWF has been the wettest with this feature
compared to previous Nam and Gfs runs. However, the latter models
have trended wetter. A slow- moving cold front is expected to
make landfall Tues Nt and Wed morning along the Pacific Nw coast.
As it does, the low level flow backs to the SE and helps to drive
an ill-defined warm front north... which puts SE Wa and the Cntrl
Idaho Panhandle in the warm sector south of the front by late
Tues. This will keep the fcst warm and sunny. We`ve been favoring
a slower trend of the cold front as far as its Ewd progression
based on model trends and pattern recognition applied to the
north-south shearing offshore trough. The downstream effects of
this shearing will be a more meridional steering flow over Ern Wa
and N Idaho, leading to a more persistent thermal ridge and warm,
dry wx likely extending into Wed for all of N Idaho and far Ern
Wa. Confidence is increasing that this stalled front will not make
much eastward progress... likely not reaching the Idaho Panhandle
until Thurs. It`s not until Thurs that we see the front become
more progressive, leading to a more widespread pcpn threat for
all of Ern Wa and N Idaho. Even with the slight chance of thunder
for Thurs, pcpn amnts should only be a few hundredths for lower
elevation towns. bz

Friday through Sunday: A slow moving trough will be pushing
through the region during this period. It is expected to begin
Friday afternoon and exit by Sunday morning. The moisture
associated with system is fairly light. Most of the region could
see some amount of precip. Temperatures will be on an up swing
during this period. The highs will be around the upper 60s for
Friday and near mid 70s by Sunday. /JDC

&&

.AVIATION...
12Z TAFS: High pressure will continue to promote dry and VFR
conditions at TAF sites with light winds. /rfox

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        88  57  85  58  82  56 /   0   0  10  20  10   0
Coeur d`Alene  87  53  85  55  81  55 /   0   0   0  20  10   0
Pullman        89  52  84  55  83  55 /   0   0  10  20  10   0
Lewiston       92  61  90  61  88  61 /   0   0  10  20  10   0
Colville       88  49  87  52  83  52 /   0   0  10  30  10  10
Sandpoint      83  46  80  50  78  50 /   0   0   0  20  20  10
Kellogg        85  54  81  55  80  55 /   0   0   0  20  20  10
Moses Lake     91  56  90  56  83  58 /   0   0  10  10   0  10
Wenatchee      91  64  88  61  81  61 /   0   0  10  20  10  20
Omak           91  55  87  56  82  57 /   0   0  10  20  10  20

&&

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

$$



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