907
FXUS66 KOTX 131015
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
315 AM PDT Tue Aug 13 2024

.SYNOPSIS...
Isolated showers and thunderstorms for southeast Washington and
the Idaho Panhandle this morning then over the northern mountains
of eastern Washington this afternoon. A break in showers and
thunderstorms comes Wednesday before more unsettled conditions
return late Thursday into the weekend. Daytime temperatures will
be near normal through the week.

&&

.DISCUSSION...
Today and Tonight: The Inland Northwest remains under a baggy upper
level trough of lower pressure. A shortwave disturbance riding
northward in eastern Oregon early this morning will bring a 15-30%
chance for showers and thunderstorms to extreme southeastern
Washington and the southern to central Idaho Panhandle through the
morning hours. Higher probabilities will be from the Northeast Blue
Mountains, to the Camas Prairie and Central Panhandle Mountains, and
then decreasing precipitously further northwest across the Palouse.
The Spokane-Coeur d`Alene corridor will be on the northern fringe of
the nocturnal convection.

Surface based afternoon convection will mainly be confined to the
northern mountains near the Canadian border. This includes the
Cascades north of Lake Chelan, over the Okanogan Highlands, and
Northeast Mountains. Bulk shear through the atmospheric column is
non-existent, and surface based CAPE of up to 500 J/kg at best will
yield weak pulse type thunderstorms. Lightning activity will be
isolated. Slow moving thunderstorms will also result in rainfall
that will limit the potential for new fire starts with lightning.
Rainfall doesn`t look particularly heavy with modest P-Wat values
near 0.9 inches. Limited instability should also result in
thunderstorms decaying fairly quickly. Risk for flash flooding
and/or debris flows isn`t particularly high. South to southwest
winds will be a little breezy into the afternoon, but not to the
point that impacts are expected.

Wednesday and Wednesday night: Higher heights build into the region
with an upper level low forming off of the coast of Oregon. This
will act to stabilize the atmosphere with benign weather conditions.
Sunny skies with temperatures warming slightly from the mid 70s and
mid 80s on Tuesday to the low to upper 80s on Wednesday. /SVH

Thursday through Tuesday: Longwave pattern shows a trough along or
just off the west coast with a ridge towards the Rockies/northern
Plains region. Forecast confidence is higher Thurs/Fri than the
weekend and beyond.

Thursday a low will move into Oregon and swing up into Washington
early Friday. This will bring an increase in clouds along with a
chance of rain and thunderstorms. The first area to watch will be
southeast WA and the southern and central ID Panhandle (much like
today). Showers with a 15-20% chance of thunderstorms moves in
late Thursday afternoon and continues through the night as
elevated instability moves into the region with enough moisture
and forcing from the low pushing east of the Cascades.

Friday morning a fair amount of the long term ensemble members are
showing light rain for much of eastern Washington and the Idaho
Panhandle. Have increased our chance of precip a bit for the
Spokane/Palouse area and most of the Idaho Panhandle with much of
the region having a 35-50% chance of rain. By the afternoon the
chance of showers and thunderstorms extends into the Cascades and
northern WA mountains. Highest probabilities of thunder will be
Lake Chelan area northward to the Canadian border, along the
US/Canadian border as well as the ID/MT border with a 25-30%
chance.

Saturday through Tuesday the models differ a bit with the
placement of the low. The closer the low is to our area, the more
likely to see near average temps or a few degrees cooler. If the
low remains further west, that will allow more of the ridge to the
east to influence and temperatures to be a few degrees above
average. Currently 25-40% of the ensembles are suggesting the
warmer solution, with 60% or more suggesting near average
temperatures. Average temperatures for mid August is mid 80s to
around 90. We look to have bouts of moisture in the south to
southwesterly flow which will keep showers and thunderstorms in
the forecast through at least the weekend. Best chance of
thunderstorms will be in the Cascades and across northern WA/ID.
/Nisbet

&&

.AVIATION...
06Z TAFS: VFR conditions will prevail. Nocturnal thunderstorms
are expected to push northeast out of northeast Oregon Tuesday
morning. These storms may impact Lewiston (KLWS) after 12z. Models
have trended slower and further south but Pullman still carries a
small chance (10%) of a thunderstorm. Expecting another round of
weak thunderstorms in far north-central and north-east Washington
and north Idaho starting around 18-21z.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Confidence is high
for VFR conditions. Low confidence in nocturnal thunderstorms for
KPUW and KLWS.

-----------------------

Confidence descriptors:
Low - Less than a 30 percent chance
Moderate - 30 to 70
percent chance
High - Greater than a 70 percent chance

For additional probabilistic information for NWS Spokane airports,
please refer to the Aviation Dashboard on our webpage:
https:/www.weather.gov/otx/avndashboard

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        81  52  84  56  87  59 /  10   0   0   0   0  20
Coeur d`Alene  80  52  82  54  86  57 /  10   0   0   0  10  30
Pullman        75  47  80  50  81  53 /  20   0   0   0  10  30
Lewiston       85  60  88  62  90  64 /  40   0   0   0  10  40
Colville       84  44  84  45  87  49 /  10   0   0   0   0  20
Sandpoint      80  50  80  51  85  55 /   0   0   0   0   0  30
Kellogg        77  55  79  58  84  60 /  20   0   0   0  10  40
Moses Lake     84  52  85  55  88  57 /   0   0   0   0   0  10
Wenatchee      85  60  86  63  88  62 /  10   0   0   0  10  10
Omak           88  58  90  60  92  61 /  20   0   0   0  10  10

&&

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

$$