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000
FXUS66 KPDT 182058
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
158 PM PDT Thu Apr 18 2024

.SHORT TERM...
Tonight through Saturday night... Dry northwesterly flow will be in
place tonight through Friday. A ridge will move over the Pacific
Northwest Friday night and early Saturday before moving eastward
later Saturday into Saturday night.

An upper level low will move to the north, generally over British
Columbia and Northern Washington by Sunday morning. The flow will
become more zonal or even slight troughing as a result, and the
pressure gradient will tighten.

There will be some breezy conditions tomorrow mainly over the
western sections of the Oregon Basin and then the Simcoe Highlands.
the NBM probabilities of winds gusting >=39 mph on Friday are 50
to 60% across the Simcoe Highlands and 30-50% across the western
Columbia Basin of Oregon. Winds will increase again Saturday
evening and continue into Saturday night, with wind gusts 30 to 40
mph mainly during this time across the Simcoe Highlands, Yakima
Valley, Columbia Basin, and Foothills of the Blue Mountains. NBM
wind gusts probabilities >=39 mph are 50-80% in the Simcoe
Highlands, Yakima Valley and and 40 to 60% in the Columbia Basin
and Blue Mountain Foothills. NBM wind gust probabilities >=47 mph
drop to 40 to 50 % across the Simcoe Highlands and Yakima Valley
and less than 20% most elsewhere.

Dry conditions are expected everywhere through later Saturday.
Then, some precipitation will impact the Cascades. Snow levels
will initially be over 7000 feet in the Oregon Cascades and over
5000 feet in the Washington Cascades, so any precipitation will
be all rain, except at the highest peaks of the Washington
Cascades. However, snow levels will fall through Sunday morning
and will be around 3000 feet, so there could be some very light
accumulations (less than 1 inch) accumulations at pass level and
perhaps a couple of inches at the higher elevations.

Elsewhere by Sunday morning, precip chances increase by Sunday
morning. However, QPF values are fairly light generally only a few
hundredths. It is also interesting that most of the deterministic
NAM is quite dry, with the GFS and ECMWF wetter.

Temperatures will be cold again tonight but look warmer than last
night. With that said, will hold off on any freeze warnings at
this time as widespread freezing conditions do not appear likely
at this time, except for the Kittitas Valley. There could be some
spotty areas that reach below freezing and this will continue to
be watched. The NBM probabilities for low temperatures <=32
degrees at Hermiston is about 25%, about 10% at Pendleton, about
30% at Yakima and upwards of 90% at Ellensburg.

Highs will be close to normal on Friday, then a few degrees above
normal on Saturday. Overnight lows should begin to warm up a bit
as well.


.LONG TERM...
Sunday through Thursday...A shortwave passing along the Canadian
border on Sunday will provide a few showers to the mountains but
otherwise cool and dry with some breezy to windy westerly winds.
This will be followed by the rebuilding of an upper level ridge
over the region providing dry seasonal conditions Monday and
Tuesday. The ridge moves off to the east Tuesday night as an
approaching upper level trough comes onshore. This trough will be
splitting with some energy dropping south towards California. The
northern portion will move inland along the Canadian border on
Wednesday followed by a deepening upper level trough over the
region on Thursday. This will increase the possibility of
precipitation on these days but with snow levels remaining 5000
feet or higher.


&&

.AVIATION...(Previous Discussion)
18Z TAFS...VFR conditions with clear skies today but then some
increasing high clouds for RDM and BDN late tonight into Friday.
Winds will become N-NE 5-15kts by afternoon and then become less
than 5 kts overnight.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  32  63  35  66 /   0   0   0   0
ALW  34  67  37  70 /   0   0   0   0
PSC  37  69  40  71 /   0   0   0   0
YKM  33  64  35  67 /   0   0   0   0
HRI  34  68  37  70 /   0   0   0   0
ELN  32  61  34  64 /   0   0   0   0
RDM  28  62  34  69 /   0   0   0  10
LGD  30  61  34  69 /   0   0   0   0
GCD  30  64  36  73 /   0   0   0  10
DLS  39  67  42  68 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Freeze Warning from 2 AM to 9 AM PDT Friday for WAZ026.

&&

$$

SHORT TERM...77
LONG TERM....91
AVIATION...91