940
FXUS66 KOTX 142258
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
358 PM PDT Wed Aug 14 2024

.SYNOPSIS...
The next weather system will move into the Inland Northwest
from the southwest Thursday afternoon. Thunderstorms Thursday
afternoon into Thursday night will bring the potential for gusty
outflow winds. This will be followed by wetter showers and
thunderstorms on Friday particularly across the Idaho Panhandle
and northern mountains. Daytime temperatures will be near normal
through the week.

&&

.DISCUSSION...
Tonight: The Inland Northwest is currently placed under a weak ridge
as an upper level low off the Oregon coast begins to move inland.
This weak ridge will bring another beautiful night across eastern
Washington and north Idaho with clear skies, light winds, and cool
temperatures.

Thursday and Friday: The upper level low will move onshore Oregon
late tonight and move northeastward into the Inland Northwest
Thursday afternoon and evening. Thunderstorms will begin over
eastern Oregon and shift northward to southeastern Washington and
the southern Panhandle Thursday afternoon. Models are showing
surface CAPE increasing to 500-1000 J/kg and across the Cascades,
southeastern Washington and the Idaho Panhandle Thursday afternoon.
The best chances for stronger thunderstorms will be focused across
southeastern Washington and the southern Panhandle where the
strongest lift and 25 to 30 knots of 0-6km bulk shear will aid in
development.  Precipitable water values climbing to over an inch
Thursday and Friday will support wet thunderstorms. The biggest
concerns will be for brief heavy rain, gusty outflow winds, and new
fire starts for lightning strikes outside the strongest
precipitation cores.  Showers will shift northward across north
Idaho and northeastern Washington overnight. Decreasing
instability after sunset will reduce the risk for lightning but
isolated strikes cannot be fully ruled out.

Focus will shift to the north Cascades and northern mountains on
Friday as a shortwave moves across eastern Washington. Models are
showing slow storm motions combined with forecasted surface CAPE of
400 to 800 J/kg. Any storms that develop will bring the risk for
lightning and heavy rainfall Friday afternoon and evening. Any
showers that form over burn scars or recently burned areas will
bring the threat for flash flooding or debris flows. /vmt

Saturday through Tuesday: Heading into early Saturday morning, a
large trough will establish itself just offshore while a ridge
simultaneously sets up to our east over the Rockies. As a result,
the Inland Northwest will be caught between the two in a stream of
southwesterly flow. Warm, moist air flowing in out of the southwest
will keep us in somewhat of an active, unstable pattern with chances
for showers and thunderstorms through the weekend and into next
week.

What we don`t know yet is exactly how far offshore the trough will
develop. The trough`s distance from the shore will play a big part
in how warm our temperatures get, how much precip we`ll see, and
where that precip will fall. Ensemble members are split 50/50 on
whether the trough will be closer to shore or further away. If the
trough is closer, temperatures will be a bit cooler, rainfall
amounts will be higher, and chances for showers and thunderstorms
will reach further east. If the trough sets up farther offshore, the
ridge to our east will have a greater influence on our weather
conditions. This means temperatures would be on the warmer side and
we`d get less rainfall, especially in the eastern parts of the
region.

Saturday looks like the most active day with widespread chances for
showers and thunderstorms. The highest chances will be over the
Cascade Crest (70 percent chance of showers and 20 percent chance of
thunderstorms). Central WA and Northern WA right along the Canadian
border will have a 30 to 50 percent chance of showers and a 10
percent chance of thunderstorms. The rest of the region including
Ritzville up to Spokane, Sandpoint, and Bonners Ferry will have
around a 20 percent chance of showers and minimal thunderstorm
chances. There is a possibility for storms to continue into Saturday
night, but instability is not looking very impressive so it`s
unlikely that storms will survive very long after the daytime
heating subsides.

Slight chances for showers and thunderstorms will pop up each
afternoon Sunday into the first half of next week mainly over the
Cascades and northern mountains. Winds will be breezy each afternoon
with gusts in the 15 to 20 mph range, but no significant wind events
are expected. /Fewkes


&&

.AVIATION...
00Z TAFS: Weather will be quiet across the Inland Northwest
this evening and Thursday morning. Look for generally light winds
and terrain driven wind shifts with mainly clear skies east of
the Cascades. Clouds will begin to increase from the south late
Thursday morning as a weather system moves into eastern Washington
and north Idaho Thursday afternoon. This will bring chances for
thunderstorms across the Cascades and southeast Washington and
southern Panhandle Thursday afternoon.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Confidence is high
for VFR conditions at TAF sites for the next 24 hours. There is
low confidence thunderstorms will make it into LWS by 00Z
tomorrow, with better chances after 00Z.

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

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        56  87  59  81  56  88 /   0   0  30  20  10  10
Coeur d`Alene  54  86  58  78  54  86 /   0  10  50  40  10  10
Pullman        48  81  52  78  51  87 /   0  10  50  20  10  10
Lewiston       62  89  63  87  62  95 /   0  20  50  20  10  10
Colville       47  88  49  80  44  86 /   0   0  20  30  10  10
Sandpoint      49  84  55  73  51  82 /   0  10  50  50  20  10
Kellogg        59  83  58  75  57  85 /   0  20  70  60  10  10
Moses Lake     54  87  56  84  55  88 /   0   0  20  10   0  20
Wenatchee      63  87  63  83  62  85 /   0  10  20  10  10  30
Omak           59  93  62  87  59  90 /   0   0  20  30  10  20

&&

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

$$