511
FXUS66 KOTX 151033
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
333 AM PDT Sun Sep 15 2024

.SYNOPSIS...

Additional light shower activity is expected Sunday and Monday.
Tuesday and Wednesday have the potential to be cool with highs in
the 60s and low 70s with periods of rain over north Idaho and the
eastern third of Washington. Winds will be breezy from the west on
Tuesday with potential for gusts near 25 mph.

&&

.DISCUSSION...
Today through Monday: A low continues to drop down the coast today,
keeping us in a southwest flow. Most of the energy will remain to
the south, but we do anticipate some light showers to slide through
the region today. Rain totals from most of these showers will be
less than 0.1", with the heaviest showers seeing slightly higher
amounts mainly in the northern mountains. Monday the low will begin
to move inland over central California, with a continued threat of
light showers mainly over the Camas Prairie and LC Valley. With this
low also comes the threat of northerly winds through the Okanogan
Valley and Waterville Plateau. Winds will gust to 25 mph today,
increasing early Monday morning through afternoon with gusts of 30
to 35 mph, before decreasing in the late afternoon. Temperatures
will be 5 to 10 degrees cooler than normal today, increasing back to
normal for Monday. /KM

Tuesday through Sunday...
The latest model runs offer insignificant changes to the ongoing
forecast. Overall, high confidence in the forecast through
Friday, then the models diverge on how the upper level pattern
will evolve through the weekend.

On Tuesday, a deep upper level trof will continue to dominate the
western US resulting in cooler than average temperatures and some
early season mountain snow over the Sierra Nevadas. As the main
lobe of low pressure ejects northward toward central Montana on
Tuesday, a deformation band will develop along its eastern flanks.
The highest probability for precipitation continues to be over western
Montana and far eastern Idaho. We expect a sharp gradient where
the precipitation shield sets up over Idaho and dry air over
eastern Washington. Probability of measurable precipitation for
eastern Washington remains less than 30% for this system. The low
moving northward will draw the southwesterly winds out of the
basin gusting 15-20 mph in the typical areas with stronger gusts
out of the east Cascade gaps.

A second reinforcing upper low will dig southward to replace the
original on Wednesday keeping the western US in the troffy
unsettled pattern. The weak instability aloft will result in
scattered clouds and a few showers mainly over the mountains
through Wednesday. Weak ridging will build over Oregon and
Washington Thursday limiting shower activity under fair skies and
temperatures in the low 70s.

By Friday, the forecast solutions begin to diverge with just over
50% of the models indicating the upper trof sliding east allowing
the ridge to continue to build over the area. The remaining model
solutions suggest another reinforcing show of low pressure
digging back over the region going into the weekend. The current
forecast package leans toward the slightly warmer and drier
solution by Saturday and Sunday.

Overall, no significant weather is expected through the next 7
days with max daytime temperatures meandering in the upper 60s to
mid 70s and overnight lows in the 40s. /AB

&&

.AVIATION...
06Z TAFS: VFR conditions will prevail for the TAF sites. There
are a couple bands of showers expected overnight, one mainly up
around the Republic area and another around Pullman and Lewiston.
On Sunday the shower band over SE WA will lift north towards
Spokane and Coeur d`Alene. Although there isn`t much organization
or forcing, and its a narrow band so still some uncertainty on its
exact placement. Thus precipitation continues to be addressed with
a PROB30 group.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
Confidence remains high for VFR conditions at the TAF sites. Given
the narrow band of rain shown by the models over far Eastern WA/N
Idaho on Sunday, prevailing conditions could develop into a steady
light rain for a couple hours in a localized nature. But
confidence still too low with precise timing, and location for
more than a PROB30 group.

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        69  49  78  52  72  48 /  30  10  10  10  20  10
Coeur d`Alene  69  49  75  50  70  49 /  40  20  10  20  40  20
Pullman        66  44  70  48  65  44 /  50  30  20  30  40  20
Lewiston       72  55  75  57  72  54 /  50  30  20  30  50  20
Colville       71  39  80  39  75  38 /  40  10   0  10  10  10
Sandpoint      67  47  74  47  68  46 /  50  20  10  20  50  30
Kellogg        68  50  73  53  65  50 /  50  30  30  30  60  40
Moses Lake     74  52  81  49  78  47 /  10  10   0   0   0   0
Wenatchee      72  54  81  54  75  55 /  20   0   0   0   0  10
Omak           74  50  82  50  80  50 /  20   0   0   0   0   0

&&

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

$$