135
FXUS66 KPDT 212255
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
355 PM PDT Sat Sep 21 2024

Updated Aviation Discussion

.SHORT TERM...Today through Monday...

Bottom Line Up Front

1. Windy through the Grande Ronde Valley through early evening

2. Quiet weather with near normal temperatures

Current observations show the most interesting thing happening
across the region is the windy conditions moving through the Grande
Ronde Valley. Surface models show a tightening of the surface pressure
gradients along the area which is leading to the enhancement of
the winds through the area. Latest obs show sustained winds of 20
mph with gusts to 26 mph. Winds will begin to settle later in the
afternoon around 5 PM as the leading edge shifts slightly
eastward and surface gradients ease.

Models are in firm agreement with an upper level flat ridge over the
forecast area today and through the remainder of the forecast
period. Monday morning a very weak disturbance will pass by along
the leading edge of the ridge bringing slight chances of light rain
over the Snoqualmie Pass area with 20% of raw ensembles showing 0.01
inches of rain. After the quick pass, things will resettle under the
ridge. Conditions across the area will remain benign through the
forecast period. EFI shows temperatures to be at or near normal with
83% of the raw ensembles putting the PDT area in the upper 60s to
low 70s, 70% showing the Basin and surrounding area seeing low to
mid 70s, central OR in the low 70s and the higher terrains in the
low to mid 60s and cooler at the crests. As the ridge continues to
settle in, temperatures will steadily increase with over 62% of the
raw ensembles putting much of the lower elevations in the upper 70s
to low 80s with 60s along the higher terrains. Bennese/90

.LONG TERM...Tuesday through Saturday...Ensemble guidance is in
fairly good agreement on the long term synoptic pattern, showing a
persistent pattern starting around the midweek onward, which may
make for some precip chances across the forecast area, especially
for our high mountain zones. Cooler air may also be on the way as we
start to head toward October.

Tuesday will be dominated by strong ridging, which could push high
temps across some of our population centers into the upper 80s and
even low 90s, which would be a good 15 to 20 degrees above average
for the time of year. Confidence on getting that warm is on the
lower end (20%), but models are in good agreement on an awfully
strong ridge with high pressure centered just to our south. This
ridge could also yield some localized unstable conditions for the
few remaining wildfire incidents in the area as well with thermal
troughing in place.

The pattern then changes Wednesday onward as ensembles bring in a
broad trough with SW winds aloft through the PacNW. Much of the
moisture transport associated with this system looks to lie to our
northwest, isolating the highest PoPs more toward the WA Cascades,
but certainly could see chances spread more to the southeast should
this trough track just a bit more southward. Once this trough moves
through, models show persistent SW flow through the region, which
will make for at least slight chance PoPs across our high mountain
zones - both the Cascades and the Blues - potentially spreading into
the lower elevations should an embedded shortwave track through. By
next weekend, ensembles start to diverge on their solutions, but
some members do suggest that the center of the upper-level low
driving this SW flow could start to inch toward our area, which
would make not only for more widespread PoPs, but for an influx of
colder air as well. Evans/74

.AVIATION...00z TAFs...VFR conditions to prevail through the
period. High level sct-bkn cigs will impact sites through the
period. Winds will be light, less than 12kts, and terrain driven
through the period. Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  45  78  49  77 /   0   0   0   0
ALW  47  80  53  80 /   0   0   0   0
PSC  49  81  55  81 /   0   0   0   0
YKM  46  80  50  82 /   0   0   0   0
HRI  47  81  53  82 /   0   0   0   0
ELN  48  79  54  83 /   0  10   0   0
RDM  39  79  45  79 /   0   0   0   0
LGD  42  77  46  76 /   0   0   0   0
GCD  41  78  45  78 /   0   0   0   0
DLS  50  83  57  85 /   0   0   0   0

&&

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

$$

SHORT TERM...90
LONG TERM....74
AVIATION...82