Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 011748

Area Forecast Discussion
National Weather Service Spokane WA
1048 AM PDT Sun Oct 1 2023


Dry and breezy conditions will be present across Central
Washington today. Cloudy conditions will be found across
Idaho and southeastern Washington. Seasonal temperatures return
next week with small chances for showers through Tuesday. For the
end of next week and weekend, we will likely see a dry and warm
pattern developing over the region.


Today: Shortwave ridging will lay down into the region from the
northwest delivering a pleasant end to the weekend. Central, much
of Eastern WA, and far North Idaho will be greeted with sunny
skies and afternoon highs in the 60s to low 70s. Winds will remain
on the breezy side coming from the north and northeast. Clouds
will be a bit more stubborn to clear out of the lower Idaho
Panhandle, especially south of I-90, and far southeastern WA due
to moisture rotating around an area of low pressure over the Great
Basin. Drier air undercutting this moisture will shift the best
chance for measurable rainfall east today toward the Clearwater
Mountains and into SW Montana but can`t rule out some sprinkles
for locations like Winchester, Lapwai, Deary, and Clarkia.
Heavier cloud cover in these areas will also keep temperatures
cooler with highs only topping out in the 50s to low 60s.

Tonight - Monday:  A shortwave comes across the top of the ridge and
tracks through the region from northwest to southeast. The system
will come through with an appreciable moisture tap but antecedent
dry air and the swift nature of this system will not equate to
much in the way of precipitation. Most locations in the lee of the
Cascades will experience passing clouds. Brief light rain or
sprinkles will be possible across Eastern WA then more organized
showers are expected as the system encounters the rising terrain
of the lower Idaho Panhandle, Blue Mountains, and Palouse.
Rainfall amounts will range from a few hundredths to up to a
quarter of an inch with the highest amounts focusing over
southeastern Shoshone County and into the Clearwater Mountains.
Latest probabilities for a tenth of rainfall are as follows:
Kellogg-40%, Pullman/Pomeroy-30%, and Winchester 55%. Light rain
is also expected along the Cascade Crest with generally light
amounts <0.10" except within the Puget Sound Convergence Zone that
is expected to form just south of Chelan County.

Winds on Monday will increase from the west and southwest with
gusts 20-25 mph expected through our Cascade gaps and across the
lower Columbia Basin. Cloud cover and some cooling of the air mass
will cool temperatures in Central and Eastern WA into the 60s but
we should see a net warming for the Idaho Panhandle also topping
out in the 60s.

Tuesday-Wednesday: The region will be under dry northwest flow as
high pressure amplifies off the coast. Models continue to
indicate a few weak waves rippling through the flow but these will
be moisture starved keeping rain chances mainly limited to
orographic favored mountains for northwest flow regimes (Central
Panhandle Mtns / Cascade Crest). Even so, the depth of the
moisture is quite shallow and limited to temperatures of -5C and
warmer so wouldn`t expect much in the way of QPF outside a
hundredth or two.

Thursday-Sunday: 90% of the ensembles members support a strong
ridge building over the region during this period. The main
differences are related to how quickly the ridge arrives over the
Inland Northwest but confidence is high for dry conditions and
above normal temperatures. It is agreed that the ridge axis will
be offshore on Thursday with 70% of the members placing it between
the WA Coast and 130W. The remaining 30% have the axis further
west between 140-150W keeping the region under the influence of
northwest flow and potential for continued showers for the Idaho
Panhandle and Cascade Crest. By Friday-Saturday-Sunday, all
members shift the ridge axis inland with dry conditions region-
wide. Some are a bit slower than others leading to minor
differences with exact temperatures. Needless to say, it should be
a gorgeous weekend across the Northwest with afternoon sunshine
and temperatures in the 70s. Large differences surface again by
early next week with models attempting to forecast the breakdown
of the ridge and potential for the bout of winds, showers, and
autumn like temperatures. More to come on this in the coming days.


18Z TAFS: Weak high pressure nosing into western Washington will
keep airports in central and most of eastern Washington clear
today with VFR conditions. Moist, northwest flow into the Idaho
Panhandle, including KLWS and KPUW, will continue to subject these
areas with mostly cloudy skies through the day with cloud bases
above 3k feet.


Spokane        64  41  62  42  64  42 /   0   0  10  20   0   0
Coeur d`Alene  62  42  62  44  61  42 /   0   0  10  20  10   0
Pullman        60  41  62  42  59  39 /  10  10  10  50  20   0
Lewiston       63  51  68  50  67  47 /  10  10  10  60  20   0
Colville       66  33  62  33  65  34 /   0   0  10  10   0   0
Sandpoint      61  38  59  39  59  39 /   0   0  10  30  10   0
Kellogg        60  45  60  47  57  44 /  10  10  20  50  30   0
Moses Lake     69  38  67  40  69  41 /   0   0  10  10   0   0
Wenatchee      69  48  67  48  69  50 /   0   0  10  10   0   0
Omak           70  45  68  44  70  45 /   0   0  10   0   0   0



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