Area Forecast Discussion
Issued by NWS Spokane, WA

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252
FXUS66 KOTX 231159
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
459 AM PDT Tue Oct 23 2018

.SYNOPSIS...
Clear skies will give way to increasing clouds this afternoon as a
storm system approaches the region. This weak disturbance may
bring some light light showers to the Cascade crest, northern ID
and far eastern WA this afternoon. More widespread precipitation
is likely Thursday as a stronger system arrives. Periods of
showers will be possible through the weekend and into the first
part of next week.

&&

.DISCUSSION...
Today through Thursday morning...It looks like there will be a
change in the weather pattern. The strong and stagnant ridge of
high pressure that has been over the western states for a while
will get bent down today and tonight as an upper level low
pressure system moves into the region. This storm system will act
as a sacrificial lamb, chasing the ridge out of the area, but will
bring little in the way of precipitation. However it will open
the door for westerly flow and weaker waves moving through the
region along the Canadian border.

Today and tonight...Some light precipitation may be possible later
this afternoon for the Blue mountains, the Camas Prairie and
possibly further north early this evening as a weak wave moves
north through the eastern zones ahead of the weakening cold front.
Confidence in anything more than a light shower is pretty low.
There will be a better chance across the Cascade crest this
afternoon, through about sunset, but even here the chance for
measurable precipitation is pretty low. The weakening cold front
will track eastward across the forecast area tonight and early
Wednesday. Expect increasing southwest winds with local gusts
10-15 mph Tuesday night and Wednesday. Southwest winds is
something that we haven`t seen around these parts in a while.

Wednesday through Thursday morning...A transient ridge of high
pressure will follow quickly behind the exiting cold front
Wednesday and Wednesday night. Mostly cloudy conditions will
result in cooler temperatures and variable clouds, but also cooler
temperatures. Tobin

Thursday through Monday: The Trof passage Thursday/Thursday night
has a well maintained tap into subtropical moisture and as such is
depicted with the highest pops and QPF of the seven day forecast.
QPF amounts are not too extreme as the system passes through quickly
and is not oriented in a manner to negate the rain-shadow effect
between the lee of the Cascade Crest and the higher terrain of North
Idaho. Additional disturbances mixed with brief and intermittent
ridging allow for continuing high pops Friday that show a decrease
Saturday. The subtropical moisture feed remains in close proximity
through Sunday evening and some models hint that weather systems
riding up its back edge develop an inflection point downstream and
that may move portions of it northward through Eastern Washington
and North Idaho as a potentially weak and wet warm front Saturday
and/or Sunday. This would be quickly followed up with a wet and
intense cold front passage late Sunday/Sunday evening as remaining
portions of the moisture fetch move through. A considerably cold and
conditionally unstable airmass makes a brief residence Sunday
night/Monday in the wake of the cold front passage. All in all it
this is quite the progressive weather pattern and as such is marked
with pops of various shape/form along with the majority of the
forecast temperatures falling on the warm side of what would be
considered normal for this time of year. /Pelatti


&&

.AVIATION...
12Z TAFS: Some high thin clouds will move through the region this
morning for VFR conditions. Localized, shallow ground and river
fog is likely to develop across favored areas this morning. KEAT
will some obscurations due to fog with vsby dropping to 3sm at
times through 1000. Then expect increasing mid to high level
clouds 20z-04z as a weak front moves through the area. The front
will also result in a wind shift to the southwest with winds less
than 10 kts. VCSH will be possible near KLWS 22z-03z but
confidence is low. Tobin



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        64  42  58  39  57  43 /  10  10  10   0  20  40
Coeur d`Alene  66  42  59  38  57  43 /  10  10  10   0  20  60
Pullman        68  43  60  39  59  43 /  10  10  10  10  10  50
Lewiston       67  47  64  43  64  48 /  10  20  10  10  10  40
Colville       64  40  60  36  57  38 /  10   0  10  10  20  50
Sandpoint      61  42  57  36  54  40 /  10  10  10   0  20  70
Kellogg        65  41  56  37  55  41 /  10  10  20  10  20  70
Moses Lake     65  39  61  37  58  42 /   0   0   0   0  30  30
Wenatchee      64  43  61  41  56  43 /   0   0  10  10  40  40
Omak           63  42  60  39  56  41 /   0  10  10  10  40  40

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until 10 AM PDT this morning for East
     Slopes Northern Cascades-Moses Lake Area-Northeast
     Mountains-Okanogan Highlands-Okanogan Valley-Spokane Area-
     Upper Columbia Basin-Waterville Plateau-Wenatchee Area.


&&

$$



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