590
FXUS66 KOTX 171151
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
451 AM PDT Sat Aug 17 2024

.SYNOPSIS...
Showers and thunderstorms will occur this evening through the
overnight hours. The area of greatest concern is central
Washington with the possibility of strong outflow winds and
lightning. Isolated thunderstorms is possible for eastern WA and
portions of the north Idaho Panhandle as well. Temperatures will
be quite warm on Saturday with dry and breezy northeast winds
across the Columbia Basin, West Plains, and southeast Washington.
Unsettled weather will continue near the Cascades on Sunday with
drier weather expected for Monday and Tuesday. Showery and cooler
weather returns by midweek.

&&

.DISCUSSION...
Today through Sunday Night: Quiet weather through the afternoon
as a brief shortwave ridge sets up across the region. Skies will
be sunny and temperatures will be in the mid 80s to lower 90s,
which is 4 to 8 degrees above average for mid August. A northeast
pressure gradient has set up and breezy winds in the afternoon
with gusts up to about 20 mph will occur across portions of the
Columbia Basin.

All eyes turn to this evening and overnight. The low pressure
sitting off the coast will push a wave up Oregon this afternoon
and into Washington this evening and overnight. Precipitable water
values increase to 150-170% of normal as the wave moves up. Both
the NAM and GFS are showing good forcing and elevated instability
moving through the region. The best chance of showers and
thunderstorms will be across central WA, but cannot rule out some
elevated thunderstorms across portions of eastern WA and north ID
as well. E WA/N ID has a 20-40% chance of seeing some sprinkles
with breezy winds and lightning as the elevated instability moves
north through the night. Further west across central WA they have
the better potential of seeing brief heavy rain, lightning and
stronger wind gusts. Some of the high resolution models are
indicating a strong gust front coming out of the line of
convection moving north into our area this evening. Right now they
show is fizzling as it moves into the Columbia Basin and
encounters the NE winds. However, the potential does exist that
these strong winds coming out of the convection will move into the
Columbia Basin, Wenatchee area and Waterville Plateau. Have kept
patchy blowing dust in the forecast for this evening and overnight
for the Columbia Basin. The convection will head north through
the night and should exit by sunrise for much of the region. The
exception is the Cascades where some of the high res models keep
small showers and thunderstorms going through the day.

Sunday will see mostly sunny skies and cooler temperatures. Winds
will be south to southwesterly following the weather system
passing through. Breezy afternoon winds with gusts 15-25 mph is
expected across portions of the Columbia Basin, Okanogan Valley,
Waterville Plateau and onto the west plains. /Nisbet

Monday through Friday: The upcoming week will feature general
upper level trough over the Pacific NW as the main upper level
ridge lies to the east over the Rockies/Great Plains. This pattern
will keep most of the heat levels down for the Inland NW although
increase the threat of showers, thunderstorms, and gusty winds.
For Monday, the circulation off the WA weakens although allows for
a mild southwest flow into the region. Anticipate very warm
temperatures for Monday with highs in the 80s to lower 90s, and
this looks to be the warmest day of the week, before a weak cold
front pushes through eastern WA into north ID with gusty westerly
winds especially in lee of the Cascades and Columbia Basin. There
is a 10-20% chance for showers and thunderstorms in the far
northern Cascades and north ID with spotty precipitation Monday
late afternoon and through the evening hours. By Tuesday and
Tuesday night, the remains of the upper trough swing through the
Inland NW accompanied with locally gusty winds, seasonal
temperatures, and afternoon showers and thunderstorms in the
northern Cascades. With the passage of the upper trough through
Tuesday night, theres a 20-30% of light showers persisting into
Wednesday with refreshingly cool temperatures in the 70s to lower
80s. By Thursday into Friday, another area of low pressure
develops off the WA coast. Slight upper level ridging will help
bring temperatures rebound back to seasonal levels in the 80s.
Models differ on the track of this feature with it either slowly
sinking southward along the west coast or weakening as it pushes
inland, which would affect the convection coverage and
temperatures. /rfox.

&&

.AVIATION...
06Z TAFS: Saturday will be quiet through the afternoon w VFR
conditions. Models are indicating a wind shift from
north/northeasterly to southerly as a weather system passes. The
shift is expected overnight. This weather system will bring a
chance of thunderstorms to central WA aft 03Z and will continue
through the night as showers and thunderstorms move north.


FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is a slight chance
of thunderstorms for portions of eastern WA and north ID, but confidence
wasn`t high enough to put in the TAF. Have mention of -shra for
GEG/SFF/COE, but given the elevated nature of the instability, it
will probably be sprinkles and a 20% chance of thunder. MWH and
EAT have the better threat of -tsra and have prob30 from 03-07Z.
With the convection brings a threat of an outflow gust front. Have
mention of gusts to 30kts, but gusts could be much stronger.


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

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        89  59  85  57  88  58 /   0  40   0   0   0  10
Coeur d`Alene  87  57  84  56  88  56 /   0  40   0   0   0  20
Pullman        89  54  82  51  82  51 /   0  20   0   0  10  10
Lewiston       97  65  92  63  92  62 /   0  10   0   0  10   0
Colville       87  49  84  46  89  48 /   0  50   0   0   0  10
Sandpoint      84  54  82  52  87  53 /   0  40   0   0   0  20
Kellogg        86  59  82  59  87  58 /   0  30   0   0  10  20
Moses Lake     94  59  85  55  88  55 /   0  50   0   0   0   0
Wenatchee      91  65  84  63  88  61 /   0  80  10   0   0   0
Omak           92  63  90  57  92  59 /   0  80  10   0   0   0

&&

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

$$