Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 231159
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
459 AM PDT THU OCT 23 2014

.SYNOPSIS...
Breezy and unsettled conditions will continue today...followed by
some light rain Friday. A strong cold front passage Saturday
Night and Sunday will produce very windy conditions with gusts
in excess of 40 mph. The pattern will continue to be active into
early next week. This includes the potential for widespread rain
into early next week as moisture associated with former typhoons
makes its way toward the Pacific Northwest.

&&

.DISCUSSION...
Today through Tonight...The occluded front and atmospheric river which
impacted much of the Inland Northwest has now shifted into
extreme eastern Washington and the Idaho Panhandle. Widespread
precipitation continues to fall along and ahead of the
front...while drier air has infiltrated areas west of the
front...with the precipitation turning increasingly showery. Thus
far most of the post-frontal showers have occurred near the
Cascade Crest and points westward. This was due to the presence of
the drier air combined with increased westerly mid-level flow over
the Cascades. This trend will likely continue through much of the
morning...with the drier air spreading slowly eastward. So for the
morning...the most widespread precipitation is expected to fall
either near the crest or over southern half of the Idaho Panhandle
and adjacent portions of southeast Washington.

Precipitation chances will increase once again during the afternoon.
This is in response to a weak shortwave trough forming just east
of 45n/130w. All model guidance depicts the current location of
this feature...and most take it over the Cascades by midday and
across the remainder of the forecast area during the afternoon.
Although this feature won`t have the deep moisture to work with as
the atmospheric river continues to sag south...it will feast off a
rapidly destabilizing atmosphere.. 500 mb temperatures ahead of
the feature will fall anywhere from 3-5c vs yesterday while the
low-level temperatures actually warm. This results in lifted index
values dropping below zero near the Cascades...as well as near the
Canadian border...most of the Idaho Panhandle and extreme eastern
Washington. MUCAPE values also rise into the 300-700 j/kg range.
Although these values aren`t terribly impressive by
themselves...model soundings suggest there will be a potential for
thunderstorms with equilibrium level temperatures at -20c or
colder. Since this is a borderline case...we don`t necessarily
expect widespread thunder...but certainly enough to warrant
throwing in the forecast. Precipitation amounts should be
generally light compared to yesterday...but the rain rates could
be considerably higher. Storms which form will likely move rapidly
northeast and could result in gusty winds to 30-40 mph.

The weather will settle down tonight as the shortwave trough pushes
east of the forecast area...and drier and more stable air
overtakes the region. Skies will generally undergo a clearing
trend...and valley fog will become an issue overnight...especially
for the northern valleys where winds are expected to remain the
lightest. fx

Fri through Sunday: No big changes for Fri and Fri Nt as the
slow-moving warm front doesn`t move north across Ern Wa until
Sat morning. Southeast flow/downslope off the Palouse should help
to keep rainfall amnts light for SE Wa and the Idaho Panhandle.
The areal coverage of the heaviest pcpn remains unchanged and
limited to a zone of upslope and modest isentropic ascent north
of a line from Moses Lake to Colville. Much of our focus has been
on the weekend fcst as the upper trough and strong sfc cyclone
lifts NE along the Pac Nw coast Sat. Model guidance is in better
agreement with the track of this low, with an overall slower
passage of the upper trough. This slower timing should allow much
of Ern Wa and N Idaho to remain dry and mild with well above
normal high temps within a northward-surging 850mb thermal ridge
of 10c-15c for SE Wa. Once fropa occurs Sat Nt, the pressure
gradient remains very tight as the deep sfc low moves into BC. We
should see 850mb winds of 40-50kts Sat Nt and Sunday as the post-
frontal dry slot axis moves across the Columbia Basin. If this
pattern remains unchanged, we`ll likely see very gusty winds Sat
Nt and Sunday that would easily reach wind advsy criteria with
gusts at or above 45 mph. Though snow levels lower Sat Nt and
Sunday potentially to 4500 ft for all mtn zones bordering BC,
significant accumulations are not expected. bz

Monday through Wednesday: The Southwest flow pattern will continue
to push waves of moisture and instability across the region during
this period. The models are in fairly good agreement on the track
and moisture associated with these waves. The wave on Monday is
trending drier than the wave on Tuesday. Warmer temperatures
associated with this pattern will keep the precip to mainly rain
with a chance of a few snowflakes in the higher elevations of the
Cascades. The entire Inland Northwest is expected to receive some
precip with the weakest chances on the East side of the Cascades.
Temperatures will be on the warming trend with highs starting
around low 50s and ending near 60. The lows will range from mid
30s to mid 40s. /JDC

&&

.AVIATION...
12Z TAFS: Moist occluded front will continue to cover the SE
forecast sites through most of the day. This will equate to
periodic or at least vicinity showers through 00z for LWS and
PUW. The shower threat will increase for all locations as a
shortwave trough crosses the Cascades around 18z...and heads into
eastern WA/north Idaho between 21-00z. Thunderstorms are a
possibility across the eastern third of Washington and the Idaho
Panhandle...as well as the threat of wind gusts from 30-40kts.
Despite the unsettled weather...cigs will generally remain in the
VFR category. Weather will dry at all sites overnight as shortwave
ridging moves in. Fog and stratus will be a possibility...but
too small to place in forecasts for now. fx

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        58  40  57  44  65  46 /  70  20  10  20  20  50
Coeur d`Alene  55  39  57  41  65  44 /  80  40  10  20  20  50
Pullman        58  42  59  47  70  46 /  80  30  10  40  10  40
Lewiston       65  46  64  46  73  48 /  70  30  20  40  10  30
Colville       56  36  59  41  66  44 /  70  30  10  50  30  70
Sandpoint      53  37  56  38  62  43 / 100  70  10  30  20  70
Kellogg        51  39  53  42  63  42 /  90  70  20  20  10  60
Moses Lake     65  40  59  45  63  48 /  50  10  10  40  20  30
Wenatchee      62  42  57  47  60  46 /  50  10  10  60  40  30
Omak           61  36  58  44  58  45 /  50  10  10  60  40  50

&&

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

$$




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