535
FXUS66 KPDT 102104
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
204 PM PDT Mon Jun 10 2024

.SHORT TERM...Tonight through Wednesday...Very little in the way
of activity across the forecast area this afternoon, as satellite
imagery only shows a few cumulus clusters developing across far
northeast OR and southeast WA. That said, breezy winds have
developed through the Cascade gaps thanks to a temperature
differential between the west and east sides of OR/WA.

Tonight, the transient ridge currently over the PacNW will be
pushed east by an approaching upper trough and attendant surface
cold front. The coupled system will remain fairly dry as it
transits the region tomorrow, with best chances of precipitation
along the coastal ranges and the WA Cascades, where there is only
a 35-45% chance of 0.01 inches of precip along the central WA
Cascade crest. Though dry, the cold front will be strong enough to
tighten pressure gradients between Portland and Spokane to around
11mb tomorrow afternoon. This will translate to breezy west winds
generally 20-30mph through the Cascade gaps, as well as the
Columbia Basin and adjacent valleys/foothills. Winds will be
stronger in the Kittitas valley tomorrow where a wind advisory is in
effect, with the probability of 24hr max sustained winds greater
than 30mph and max gusts greater than 45mph are between 75-95%.
While the NBM does show similar probabilities of these wind
speeds/gusts in the Columbia Basin, HREF members keep winds below
criteria, and without the support of an 850mb jet confidence in
windy conditions is only 50-60%.

The shortwave and cold front will exit the forecast area tomorrow
evening, allowing winds to diminish through the late evening and
overnight hours. Wednesday, a zonal flow aloft will be the
dominant pattern throughout the day, resulting in locally breezy
to breezy winds through the Cascade gaps and overall dry
conditions across the forecast area. Lawhorn/82


.LONG TERM...Thursday through Monday...A cooler, wetter pattern is
in store for the forecast area as ensemble guidance keys in on a
deep upper-level low that looks to envelop the region by sometime
next weekend. As a result, expect below-average temperatures,
persistent PoPs - especially across our mountain zones - and periods
of breezy winds across much of the CWA.

This upper-level low, initially centered off BC, will impact the
area in two distinct waves: the first via a band of amplified SW
flow aloft through the leading edge of the system, which is expected
to begin around the midweek and last through the beginning of next
weekend, and the second via the arrival of the low`s center itself.
Ensemble guidance does disagree on the exact track of the low, as
some members have the system skirting us more to the north, while
others bring the center of the low more overhead of the PacNW. A
more northward track of the low would invite a wetter forecast, as
moisture advection would be more persistent into the area, while the
low`s center falling overhead would bring in colder air, but not
quite as wet of a forecast. Still, confidence is high (60-70%) that
temps late this week and over the weekend will fall below average
starting Saturday, to around 5 to 10 degrees below seasonal values,
possibly more should the low track a bit more southward.

Confidence is also high (60%) that our mountains will see a wet
forecast for most of the period. QPF isn`t particularly impressive
this far out, but the pattern is conducive for showers for much of
the period. Would expect some higher PoPs across the lower
elevations given the pattern depicted across deterministic guidance
as well, but I suspect that model climatology is playing a role
here. Models do tend to be a bit gun-shy this time of year with
regards to depicting precip outside of the mountains during the long
term.

Expect winds to rear their ugly heads once again due to this low`s
influence as well. EFI doesn`t quite tap into extreme wind values
for the forecast area as of now, but NBM probabilistic guidance does
depict high probabilities (50-80%) for wind gusts to exceed 30 mph
across much of the forecast area Friday through the weekend.
Evans/74


&&

.AVIATION...18z TAFs (Previous Discussion)...VFR conditions
expected for the period. Expect clear skies and light to moderate
terrain- driven winds across all sites, with the breeziest winds
occurring at DLS, PDT, and ALW. Gusts may exceed 20 kts at times
in particular for DLS. Evans/74


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  55  83  47  77 /   0   0   0   0
ALW  59  87  50  79 /   0   0   0   0
PSC  60  90  52  82 /   0   0   0   0
YKM  56  83  46  80 /   0   0   0   0
HRI  58  87  50  82 /   0   0   0   0
ELN  55  75  46  74 /   0   0   0   0
RDM  51  81  42  76 /   0   0   0   0
LGD  52  82  44  74 /   0   0   0   0
GCD  53  85  45  79 /   0   0   0   0
DLS  58  79  50  79 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Wind Advisory from 9 AM to 11 PM PDT Tuesday for WAZ026.

&&

$$

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