073
FXUS66 KPDT 131757 CCA
AFDPDT

Area Forecast Discussion...CORRECTED
National Weather Service Pendleton OR
1057 AM PDT Mon May 13 2024

.AVIATION...18z TAFs...Widespread VFR with dry conditions through
the TAF period. Gusty winds will be present through the afternoon
and remain the forecast challenge. Guidance indicates a high
chance (70-100%) for gusts of at least 22 kts for today across
most terminals. The focus for the strongest wind lies between
KDLS and KYKM where a high chance (75-95%) for gusts of 34 kts
today. Winds are anticipated to lessen through the later portion
of the forecast period, especially after around 10z Tuesday.
Branham/76

&&

.PREV DISCUSSION... /issued 935 AM PDT Mon May 13 2024/

UPDATE...Current radar and visible satellite imagery showing dry
conditions as some high level clouds stream in from the northwest,
pushing into the Yakima Valley. This is in response to an upper
level shortwave that is passing across the area later this morning
and through the afternoon, elevating winds and slightly increasing
cloud cover. A pressure gradient is expected to develop along the
Cascades, increasing winds through the Kittitas Valley, Simcoe
Highlands, Eastern Gorge, and the northern Blue Mountain
foothills. The GFS and the NAM both suggest a pressure gradient
between Portland and Spokane of 10-11 mb, peaking between 2 PM and
11 PM this afternoon/evening. Thus, a Wind Advisory has been
issued through 11 PM Monday night for the Kittitas Valley as gusts
of up to 50 mph will be possible. Confidence is high (70-80%) of
advisory-level winds occurring across the Kittitas Valley as the
NBM highlights an 86% chance of wind gusts of 47 mph or greater,
and a 52% chance of wind gusts of 55 mph or greater for
Ellensburg.

The other weather concern resides with elevated river levels on
the Naches River as the station near Cliffdell is forecast to
reach action stage later this morning. The current river level is
28.85 feet and is forecast to reach action stage (29 feet) by 11
AM before slowly peaking Friday morning at 29.46 feet. At this
time, there is high confidence (>95%) of reaching action stage and
a low chance (<5%) of reaching minor flood stage (31 feet). The
Naches River near Naches is also currently forecast to reach
action stage (16 feet) Thursday morning before peaking at 16.14
feet early Friday morning. However, confidence in reaching action
stage is moderate (46%), with a low chance (<5%) of reaching minor
flood stage. 75

SHORT TERM...Today through Wednesday...An upper level shortwave
trough will pass over the region today producing breezy to windy
conditions but very little if any precipitation. Sustained winds
of 15 to 30 mph with gusts around 40 mph will be common throughout
the lower elevations. The Kittitas Valley is expected to see a
little stronger winds with gusts 45 to 50 mph so a wind advisory
is in effect through this evening. The winds will usher in some
cooler air with high temperatures running 5 to 15 degrees cooler
today compared to Sunday.

The trough will exit to the east overnight with a ridge of high
pressure in its wake building over the eastern Pacific Ocean. This
will keep the forecast area under a dry northwest flow Tuesday
through Wednesday with lighter winds. Temperatures will remain
steady to slightly warmer on Tuesday and then rise another 5
degrees or so on Wednesday.

LONG TERM...Thursday through Monday...Not much of a change to the
forecast through the long term. Temperatures remain steady with dry
conditions continuing  through the lower elevations. There continues
to be below 15% probabilities of rain along the far northern
Cascades and increasing to 22-36% probabilities Sunday into Monday.

Models are in firm agreement with the upper level high shifting
slightly southwest away from shore and broadening the upper level
flow as an upper level shortwave moves down the coast of B.C..
Clusters shows there is a timing and positioning variance between
the models however. Both Thursday and Friday have signaled an
increase in the cross Cascade pressure gradient which will increase
the chances of westerly flow and windy conditions beginning in the
Kittitas Valley and progressing southward through the day. Latest
raw ensembles shows there is 20-30% chance of the Gorge and lower
Columbia Basin seeing sustained winds of 25 mph, 40-60% along the
Simcoe Highlands and through Kittitas Valley. These chances increase
to 30-40% through the Gorge and lower Columbia Basin and Kittitas
Valley and 40-60% along the Simcoe Highlands. Confidence in the
winds in moderate with the timing being the largest variance. EFI is
showing a slight increase in above normal temperatures mainly
through the Basin with the NBM putting temperatures in the upper
80s. Over 70% of the raw ensembles put the entirety of the Columbia
Basin, Gorge, foothills of the Blues and John-Day Basin above 80
degrees dropping to the upper 70s to low 80s by Friday. The
shortwave passage also brings a less than 15% probability of rain to
the higher elevations of the far northern Cascades near Snoqualmie
Pass.

Saturday and Sunday confidence between the models lessens a bit more
with the timing and the strength of the upper level low. EURO shows
the shortwave to broaden bringing increased chances of rain while
the GFS tightens into an upper level low with precipitation locked
against the Cascades.  Models also show a surface embedded cold
front ahead of the upper level system which will bring a decrease in
the temperatures Saturday. EFI shows the temperatures Saturday and
Sunday to moderate to near normal with 70-80% of the raw ensembles
showing the aforementioned areas dropping nearly 10 degrees Saturday
steadily increasing Sunday. Guidance shows the winds to shift to a
more northwesterly component allowing diurnally breezy conditions
with 70% probabilities for the more wind prone regions to see near
20 mph winds.

Lastly, models fall out of phase by Monday with the Euro bringing in
a brief transient ridge ahead of another upper level low while the
GFS keeps the original low overhead and deepening across the region.
With that, let the NBM take the reins which has 22-36% probabilities
of rain along the northern Cascades , light westerly winds and
temperatures in the upper 70s for the lower elevations. Bennese/90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  76  46  74  49 /   0   0   0   0
ALW  79  50  76  53 /   0   0   0   0
PSC  83  53  81  54 /   0  10   0   0
YKM  79  46  81  49 /   0   0   0   0
HRI  81  50  80  51 /   0   0   0   0
ELN  71  47  76  51 /   0   0   0   0
RDM  73  41  73  44 /   0   0   0   0
LGD  73  44  72  45 /   0   0   0   0
GCD  74  42  73  44 /   0   0   0   0
DLS  75  50  81  54 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory until 11 PM PDT this evening for WAZ026.

&&

$$

UPDATE...75
SHORT TERM...91
LONG TERM....90
AVIATION...76