103
FXUS66 KPDT 160911
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
211 AM PDT Thu May 16 2024

.SHORT TERM...
Today through Saturday night...
High pressure off the coast will be suppressed to the southwest
later today and tonight by a strong shortwave and upper level
trough that will drop down from the northwest. This trough and
shortwave will move across the area tonight into Friday morning
before moving east of the region. Another shortwave will move
across mainly eastern sections of the area on Friday. Dry
northwesterly flow will return for Friday night into early
Saturday before yet another trough and shortwave move
southeastward across Washington during the day on Saturday into
Saturday night.

As the trough approaches, it will bring precipitation first to
the Washington Cascade crest, then to the Oregon Cascade crest and
Blue Mountains. QPF is expected to be light, only a few
hundredths, with the exception of the Washington Cascades which
could see over a tenth of an inch and possibly up to 0.20 inches.

Snow levels will start off over 8000 feet, but by Friday morning
will be around 3000 feet in the Washington Cascades and 4500 to
5000 feet elsewhere, so it is possible there could be some very light
snow at or above these levels.

The biggest concern continues to be gusty winds ahead of and with
the passage of the trough. Based on the latest data, a wind
advisory will be issued for the Kittitas Valley, Simcoe Highlands,
Oregon Columbia Basin, Columbia Gorge, and Oregon Foothills of the
Blue Mountains. Winds of 25 to 35 mph with gusts 40 to 50 mph are
expected. NBM probabilities of wind gusts >= 39 mph are 90 to 100%
in these areas today. NBM probabilities of wind gusts >= 47 mph
range from 60 to 80% in these areas. The ECMWF EFI has these same
areas generally in 0.6 to 0.7, with some embedded locations of 0.7
to 0.8.

Breezy conditions are expected to continue behind the trough as
well through much of Friday, and winds will increase with the
approach of the next shortwave later Friday into Friday evening.
Breezy to windy conditions will occur again on Saturday with the
approach of the next trough on Saturday. Additional precipitation,
mainly over the mountains is possible later Saturday into
Saturday night, but QPF should be less than the event tonight into
Friday.

High temperatures will be about 10 degrees above normal today,
but then will drop to near normal on Friday and Saturday.


.LONG TERM...
Sunday through Thursday...Models coming into better agreement on
what looks to be a relatively active pattern through most of next
week, filled with chances for showers and potentially mountain
thunderstorms as a couple of upper-level lows look to impact the
region.

For Sunday, the forecast area will fall on the southern flank of an
ongoing low situated over western Canada, inviting a band of
amplified NW flow over the PacNW. Light orographic shower activity
is possible across the crests of our mountain zones, however chances
are on the lower end (20-30%) as the western Canada low will help
usher in a pretty dry airmass overhead through much of the weekend,
with PWATs reading in the 0.3 to 0.5 inch range. Such a pattern will
invite breezy winds across the Cascade Gaps as well, namely through
the Columbia River Gorge, Kittitas Valley, and Simcoe Highlands.

Better chances for area-wide showers look to occur later in the work
week as a well-developed upper-level low is shown dropping down into
the forecast area from the Gulf of Alaska by around Tuesday. Given
this system`s northwesterly approach, not expecting particularly
heavy rain, but lift will be much more supportive for shower
activity Tuesday into Wednesday. Some of these showers may develop
into thunderstorms across primarily the eastern mountains, should
lift prove to be suitable enough, however the pattern thus far
doesn`t look to be conducive for particularly strong storms, as
temps will be right at or just below seasonal averages under this NW
pattern, which would mean generally 50s and 60s for daytime highs
across the eastern mountains. QPF guidance isn`t particularly
precise this far out, but NBM does depict widespread PoPs in the 25-
50% range Tuesday into Wednesday, increasing across our mountain
zones.

Ensembles and deterministic guidance are a bit shaky beyond the
midweek next week, as to be expected under a relatively progressive
pattern, but ensemble clustering does hint at continued troughing
across the PacNW. Expect a continuation of persistent shower
chances, roughly seasonable temps, and breezy winds should these
ensemble members verify. Evans/74

&&

.AVIATION...
12z TAFs...VFR conditions expected, with the main concern through
the period being gusty winds across all sites. By the late morning,
winds will pick up primarily out of the west, gusting up to and
even over 30 kts at times, especially for DLS and PDT, where winds
are expected to be the strongest. Skies will generally be clear
outside of some high clouds. Gusty conditions are expected to
carry over into the overnight hours and pick up once again heading
into Friday. Evans/74

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  77  44  65  40 /   0  10   0   0
ALW  80  48  68  45 /   0  20   0   0
PSC  85  50  72  45 /   0  10   0   0
YKM  80  39  70  39 /   0   0   0   0
HRI  82  47  70  44 /   0  10   0   0
ELN  72  40  63  42 /  10  10   0   0
RDM  78  42  65  34 /   0   0   0   0
LGD  77  45  60  36 /   0  10   0   0
GCD  79  46  62  36 /   0   0   0   0
DLS  74  49  67  45 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 11 AM this morning to 11 PM PDT this evening
     for ORZ041-044-507.

WA...Wind Advisory from 11 AM this morning to 11 PM PDT this evening
     for WAZ024-026-521.

&&

$$

SHORT TERM...77
LONG TERM....74
AVIATION...74