583
FXUS66 KOTX 131002
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
302 AM PDT Mon May 13 2024

.SYNOPSIS...
An approaching system will deliver breezy conditions Monday,
especially closer to the Cascades and western Columbia Basin. A
chance for showers will come to the Cascade crest, northeast
Washington and the northern Idaho Monday, lingering over Idaho
Tuesday. Temperatures will cool for Monday and Tuesday, rebound
around midweek, then decrease again later in the week as the next
shower and breezy winds chances come in.

&&

.DISCUSSION...
Monday: A dry, shortwave trough is currently moving across the
northwest early this morning, evident on satellite imagery as a
band of high level clouds pushing across the northwest. A
tightening cross-Cascade pressure gradient is bringing breezy
northwest winds through the Cascade gaps with sustained winds of
15 to 25 mph currently being observed. Expect these winds
strengthen through Monday morning, peaking in the afternoon and
the early evening across central Washington with wind gusts up to
45 mph. The National Blend of Models is giving the higher
elevations across the Waterville Plateau a 60% chance to see wind
gusts over 45 mph. Other locations in central Washington such as
Wenatchee, Bridgeport, Malott, and Ephrata are carrying a 30-40%
chance for wind gusts over 45 mph. Winds will also increase across
far eastern Washington and north Idaho through Monday afternoon,
but are not expected to be strong compared to central Washington.

As the shortwave passes through far eastern Washington and north
Idaho in the late morning and afternoon, areas across the
northeast Washington and the north Idaho mountains will see
chances for showers and thunderstorms. Model soundings indicate
the best chances for lightning to be for areas closer to the
Canadian border, where the steepest mid level lapse rates and
orographic lift enhance the potential Monday afternoon. Another
shortwave moving through late Monday afternoon will continue the
chances for showers and isolated thunderstorms into the evening
for these areas.

Temperatures today will be about 5 to 10 degrees cooler compared
to Sunday with widespread highs in the 70s. Some lower locations
in the Columbia Basin and the L-C Valley could peak slightly above
80.

Tuesday: Chances for showers will continue across north Idaho
early Tuesday on the backside of the shortwave as the upper level
ridge begins to rebound from the west. Winds will begin to shift
to the north early Tuesday morning and funnel down the Okanogan
Valley through Tuesday afternoon with sustained wind speeds of
10-20 mph and gusts of 25-30 mph. They will shift back to the
west-northwest Tuesday evening with another breezy evening through
the Cascade gaps. /vmt

Wednesday and Thursday: Temperatures will rebound Wednesday as a
warm ridge of upper level high pressure builds off the West Coast,
and summer-like temperatures may persist into Thursday. The
medium range models bring a shortwave over the top of the ridge
Wednesday night into Thursday leading to differences in the
Thursday forecast including the timing of a cold front. Confidence
is relatively high that Wednesday will feature partly to mostly
sunny skies with high temperatures ranging from the mid 70s across
the Idaho Panhandle to the mid 80s in central/north central
Washington. With differences in frontal timing Thursday, a few of
the ensemble members make Thursday the warmest day of the week
while others suggest Thursday will be about 10 degrees cooler than
Wednesday. Guidance from the National Blend of Models (NBM)
illustrates the spread in the ensembles with the 90th percentile
generating highs in the mid 80s to low 90s while the 10th
percentile has highs in the mid 60s to mid 70s. Chances are good
that Thursday will be breezy whether is warm/breezy ahead of the
front or cool/breezy behind the front.

Friday through Sunday: The forecast Friday into the weekend
becomes more complicated with a developing split flow pattern by
the end of the week. With the southern branch of the Polar Jet
along the Mexican border and the northern branch carving into the
Northern Rockies there is a good deal of variability in the medium
range models. The NBM forecasts daytime temperatures cooling into
the 60s and 70s Friday, Saturday and Sunday with a 20 to 30
percent chance of showers over the mountainous terrain of north
Idaho, northeast Washington, and the northern Cascades. This is a
"middle of the road" forecast while the evening run of the GFS is
an example of a statistical outlier. The deterministic GFS
drags an upper low south through Washington and Oregon Saturday
and Sunday. Fewer than 15 percent of the GFS, ECMWF, and Canadian
ensembles look similar to the chilly and rainy GFS next weekend.
/GKoch


&&

.AVIATION...
06Z TAFS: A pair of cold fronts push through the region over the
next 24 hours. The first front has pushed into W WA and will swing
across the forecast area overnight. A second front arrives Monday
evening 00-03z with more of a northwest orientation. Winds will
remain breezy through the night with gusts near 30kts possible
especially in the Cascade gaps. There will be a small risk for
marginal LLWS in advance of the front. The front first front will
deliver little to no precipitation. The second front will bring a
20-40% chance for showers across far NE WA and N ID mainly north
of a line from Kellogg to Colville. North Idaho has a 15% chance
of thunder after 18z Mon. Generally VFR skies are expected
region-wide outside some mountain obscrns on the higher peaks.
The main impact for most terminals will be gusty west to southwest
winds. Wind gusts of 20-30 mph are anticipated for most terminals
between 19-03z Monday afternoon-evening. KEAT could experience a
few periods of winds closer to 40 mph which were added as a tempo
group.  /sb


FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
There is high confidence for gusty winds with a transition in air
masses occurring in the next 24 hours. Confidence is low for
rainfall in NE WA and N ID and general pilots should be aware of
virga showers producing gusty, erratic winds. Winds could decouple
sooner than expected for sites after sunset leading to lower
confidence for exact wind speeds.

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

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        74  47  74  48  79  53 /   0  10   0   0   0   0
Coeur d`Alene  72  46  71  47  76  51 /  10  10   0   0   0   0
Pullman        70  46  69  48  74  51 /   0  10   0   0   0   0
Lewiston       79  52  76  52  83  56 /   0  10   0   0   0   0
Colville       76  44  76  45  81  47 /  20  20   0   0   0   0
Sandpoint      72  47  70  46  74  49 /  20  30  10   0  10  10
Kellogg        69  49  67  50  73  53 /  10  20  10   0   0  10
Moses Lake     79  48  81  50  86  53 /   0   0   0   0   0   0
Wenatchee      74  50  79  54  83  57 /   0   0   0   0   0   0
Omak           79  48  81  50  85  53 /  10   0   0   0   0   0

&&

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

$$