550
FXUS66 KPDT 121643 AAA
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
943 AM PDT Sun May 12 2024

Updated Aviation Discussion

.MORNING UPDATE...Satellite imagery this morning shows clear skies
across the forecast area, though a fire in central Klamath county
did push smoke aloft across portions of Deschutes, Crook, and
Grant counties. Today, an upper ridge over the area will bring
another round of dry and warm conditions, then push east into
ID/MT by this evening. However, west to northwest winds will
increase through the Cascade gaps into the OR Columbia Basin this
afternoon. Winds will be 15-25 mph with gusts up to 35 mph, and
locally 40-45 in portions of the Kittitas valley this afternoon.
Afternoon temperatures in the Lower Columbia Basin in WA and the
Yakima valley will warm into the upper 80s to low 90s, with upper
70s to mid 80s across the rest of the lower elevations. Lawhorn/82

&&

.PREV DISCUSSION... /issued 224 AM PDT Sun May 12 2024/

SHORT TERM...Today through Tuesday...The upper level ridge over the
region will move off to the east today as a low amplitude trough
approaches from the west. This will bring the onset of a marine push
in the afternoon with increasing westerly winds of 15-25 mph and
gusts around 35 mph along the east slopes of the Cascades that push
out into the Columbia Basin through the afternoon and evening. This
will result in temperatures across the western portion of the
forecast area being 4-8 degrees cooler on Sunday while the eastern
portion remains unchanged from Saturday`s highs. Winds will remain
breezy Sunday night and then increase further on Monday with the
trough passage boosting winds another 5-10 mph. This could bring
wind speeds and or gusts close to advisory levels in portions of the
COlumbia Basin and especially the Kittitas Valley. Precipitation
looks to be limited to a few showers in the central and northern
Washington Cascade crest. There is also a very low 5-10% chance of
precipitation over the far eastern mountains in the Monday afternoon
and overnight period. On Tuesday the trough moves into the northern
Rockies and a ridge of high pressure over the eastern Pacific begins
moving into the PacNW. This will bring a reduction of winds and
maintain highs in the 70s to around 80 in the lower elevations and
60s in the mountains.

LONG TERM...Wednesday through Sunday...The long term will be
characterized by relatively benign weather. Temperatures will
moderate back to near normal and precipitation will remain nill
until chances slightly (<25%) towards the end of the period, but
only in the higher peaks of the WA Cascades. All in all, a typical
late spring pattern up ahead.

Wednesday and Thursday models are in firm agreement with an upper
level high pressure system parked off the coast of OR bringing
mostly a northwest flow across the forecast area. Ensembles clusters
are in agreement with the ridge with the main variance being in the
amplitude. Regardless of this fact, dry and warm conditions will
occur Wednesday and Thursday with over 90% of the raw ensembles
showing the entirety of the Columbia Basin seeing temperatures in
over 75 degrees as well as the Gorge, foothills of the Blues and
Yakima/Kittitas Valleys. 40-60% show central and north central OR
above 75 degrees as well as the John Dy Basin.  Lastly, well over
90% of the ensembles show the remainder of the forecast region to be
above 65 degrees with the highest peaks in the 50s.

Thursday night through Sunday models show the upper level high
pressure ridge begins to traverse southward ans an upper level
shortwave makes it way into the PacNW. However, clusters show there
to be a wide variance in the positioning and timing of the incoming
shortwave. ECMWF brings it in faster and farther to the north of the
area enhancing precipitation chances across the far northern
Cascades. The GFS however, brings it in closer to Friday evening.
With this shortwave, temperatures will cool slightly across the
forecast area and will bring with it less than 15% probabilities of
precipitation to the far north Cascades through Saturday increasing
to 25% Sunday. However by Sunday models fall out of agreement with
ECMWF suggesting a a continued trough while the GFS brings back
another ridge. Another thing of note with the incoming shortwave
will be the increase in winds, especially through the Cascades Gaps
as the shortwave causes the cross Cascade pressure gradient to
increase with the more westerly upper level flow. Highest winds are
expected Thursday night with the initial passage of the shortwave
with with 50-70% probabilities of sustained winds up to 25 mph,
decreasing in speed slightly each day thereafter. EFI continues to
show the region to be under climatological normal temperatures with
over 60% of the ensembles showing temperatures to average 70-75
degrees across the majority of the region with a few isolated
locations in the Basin seeing low 80s. Bennese/90

.AVIATION...18Z TAFs...VFR with mostly clear skies for all TAF sites
through the forecast period. Winds will be 10 to 15 kt with gusts
around 20 kt this afternoon and early evening except gusts around 25
kt at KDLS, decreasing and becoming terrain driven overnight. 78

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  82  52  75  47 /   0   0   0   0
ALW  84  56  78  51 /   0   0   0   0
PSC  90  57  82  52 /   0   0   0   0
YKM  86  51  79  45 /   0   0   0   0
HRI  86  55  80  50 /   0   0   0   0
ELN  80  54  71  47 /   0   0   0   0
RDM  77  44  74  40 /   0   0   0   0
LGD  79  47  73  44 /   0   0   0   0
GCD  79  46  75  42 /   0   0   0   0
DLS  82  54  74  50 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

MORNING UPDATE...82
SHORT TERM...91
LONG TERM....90
AVIATION...78