070
FXUS66 KPDT 131110 AAA
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
410 AM PDT Thu Jun 13 2024

Updated Aviation Discussion

.SHORT TERM...Today through Saturday night...Mostly clear skies
and a dry air mass have led to efficient radiational cooling for
most areas, resulting in cool temperatures nearly area-wide.
After the chilly start to the morning, temperatures will increase
this afternoon with another warm, dry day anticipated across the
forecast area. Winds will be light through afternoon, but a sharp
up-ramp in winds is anticipated this evening through the Cascade
gaps and into the Columbia Basin as onshore-directed pressure
gradients strengthen in response to an approaching trough.
Forecast soundings indicate a 30-40kt LLJ over the Columbia River
Gorge (CRG) and Kittitas Valley (KV) this evening through Friday
morning. Confidence is high (80% chance) that wind-prone
locations in the KV will approach or exceed 45 mph wind gusts so
have opted to issue a Wind Advisory, valid 8PM this evening until
11AM Friday morning. In the CRG and across the adjoining portions
of the Columbia Basin (CB), north-central OR (N-C OR), and the
foothills of the Blue Mountains (BMF), confidence is moderate
(40-60% chance) in winds reaching advisory criteria so have opted
to forgo any highlights. Of note, the nocturnal nature of the
event decreases confidence relative to a daytime event.

Friday, winds will remain breezy to windy as the first in a series
of shortwaves wraps around a deep, upper-level closed low and
ejects northeastward into northern WA and southern BC. Due to the
trajectory of the impulse, precipitation chances (15-60%) will be
confined to the Cascade crest of WA on Friday.

Saturday, the second shortwave is advertised to punch across the
forecast area, resulting in another round of breezy to windy
onshore winds. Winds may approach advisory criteria for wind-
prone locations such as the KV, CRG, and portions of the CB and
BMF (50-80% chance), but have opted to hold off on any highlights
for now.

Precipitation chances will increase Saturday, but the best chances
(60-90%) will still be pinned to the Cascade crest. Elsewhere,
chances are <15% for most of the CB and central OR (C OR), while
chances are higher (15-40%) for the BMF and Blue Mountains (BM).
Confidence is low (<20% chance) in thunderstorms Saturday
afternoon, but steep low- and mid-level lapse rates will lead to
modest instability. Plunkett/86

&&

.LONG TERM...Sunday through Thursday...The forecast starts out
on Sunday with some discrepancies on the timing and location of an
upper low that will impact the region early next week. The
majority of the clusters favor a more offshore solution on Sunday
similar to the deterministic GFS compared to the more progressive
ECMWF. This will keep shower activity (30-40% chance) confined to
the Cascade crest during the day on Sunday.

On Monday and Monday night rain showers will spread across the
region as the upper low moves across the region...with the
potential for wrap around precipitation over the foothills and
Blue and Wallowa Mountains on Tuesday. There is a low chance
(10-20%)of TSTMS Monday afternoon and evening mainly in Grant
County but any storms will remain rather isolated and brief given
marginal instability.

QPF amounts Monday through Tuesday are forecast to be around
.50 inches in the Foothills of the Blues and around 1.00 inch in
the eastern mountains with lighter amounts elsewhere. Right now
there is a disconnect between the NBM QPF and POPS. Despite the
higher QPF amounts the POPS are modest at only 30-50%. Considered
bumping POPS up but the ECMWF and GFS ensemble members show
considerable spread in QPF amounts with some members showing heavy
QPF and others none at all (at KPDT and KMEH for reference).
Roughly 10% of the ensemble members are indicating the potential
for rainfall exceeding 1.00 inch at KPDT and 2.00 inches at KMEH.
Think the QPF and POP inconsistency will decrease with time as the
event gets closer.

The clusters show considerable spread on how quickly the upper low
moves east of the region on Wednesday. Went with the NBM which
dries things out on Wednesday but if the low exits the region
more slowly, there could be lingering showers over the northeast
mountains.

There is low-moderate confidence (40-50%) in the forecast for
Thursday given the differing cluster solutions. It does appear
that the flow will be slightly less amplified which will allow
temperatures to warm up. In fact after high temperatures bottom
out at 10-15 degrees below normal Sunday and Monday a warming
trend will occur through Thursday such that high temperatures will
be right about normal Thursday afternoon. 78

&&

.AVIATION...12Z TAFS...VFR conditions are expected through the
period with increasing clouds at 15-25 kft AGL. Winds will be 5-12
kt except 15G25kt late this afternoon and tonight at KDLS...KRDM and
KBDN. 78

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  83  51  73  48 /   0   0   0   0
ALW  86  55  77  51 /   0   0   0   0
PSC  88  56  80  54 /   0   0   0   0
YKM  85  48  76  46 /   0   0   0   0
HRI  88  55  79  52 /   0   0   0   0
ELN  82  49  71  45 /   0   0   0   0
RDM  82  42  72  41 /   0   0   0   0
LGD  84  49  72  45 /   0   0   0   0
GCD  88  48  75  43 /   0   0   0   0
DLS  84  51  73  51 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory from 8 PM this evening to 11 AM PDT Friday for
     WAZ026.

&&

$$

SHORT TERM...86
LONG TERM....78
AVIATION...78