687
FXUS66 KPDT 281710
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1010 AM PDT Fri Jun 28 2024

Updated Aviation Discussion

.AVIATION...18Z TAFs...All sites remain VFR for this period with
current few to sct clouds. Mid to high clouds with light winds will
prevail during the next 24 hours. Feaster/97

&&

.PREV DISCUSSION... /issued 302 AM PDT Fri Jun 28 2024/

SHORT TERM...Today through Sunday...Water vapor satellite imagery
tonight shows an upper trough departing into central MT, while a
transient upper ridge sits offshore the PacNW. The upper trough
passage earlier supported breezy winds across the forecast area,
however those winds have been steadily decreasing tonight, and are
expected to become light by the morning hours.

Today, the transient upper ridge offshore will transit the PacNW
as the trough to in MT continues east. The upper ridge will bring
dry conditions with light winds across the region, while also
facilitating a warming trend of 4 to 6 degrees as compared to
yesterday afternoon`s temperatures. Upstream of the upper ridge,
an upper trough associated with a low in the Gulf of Alaska will
begin to amplify. Rounding this amplifying trough Saturday will
be a shortwave impulse that will lift into southern BC by the late
afternoon. This shortwave will bring a marine push through the
Cascade gaps beginning Saturday morning, resulting in breezy winds
with gusts 30-35mph developing through Kittitas valley, eastern
Gorge, and portions of the Columbia Basin (confidence 70-85%). The
upper impulse will also clip the central WA Cascades during it`s
transit in the afternoon, resulting in only a slight chance
(15-20%) of showers in this area. Though the ridge will have exit
to the east, the Columbia/John Day Basins will see temperatures
warm another 4 to 5 degrees Saturday afternoon, with all other
locations only seeing a 1 to 2 degrees increase.

Late Saturday into Sunday, the upper trough will push onshore,
bringing slight chances(15-25%) of scattered showers across the
Blues and Wallowas. An attendant cold front with the trough will
push across the forecast area during the afternoon Sunday,
increasing winds through the Cascade gaps and across the lower
elevations. The typically breezy to locally windy areas of the
Kittitas valley, Simcoe Highlands, OR Columbia Basin, and southern
Blue mountain foothills will see a 70-85% chance of meeting or
exceeding a 24-hr peak wind gust of 45mph. Otherwise, the cold
front will tap into weak surface instability with modest low
level lapse rates in Wallowa county, resulting in slight chances
(~15%) of isolated thunderstorms in the afternoon. Lawhorn/82

LONG TERM...Monday through Friday...The long-term period is
expected to begin with an upper-level trough over the region on
Monday, subsequently replaced by drier northwesterly flow aloft
and rising heights as an offshore upper-level ridge likely (80-90%
chance) propagates eastward beginning on Tuesday. Troughing to
the north over the Northern Rockies will likely (90-100% chance)
result in breezy to windy westerly winds through the Cascade gaps
through Wednesday. While no Red Flag conditions are currently
forecast, the combination of the aforementioned wind and low
relative humidity in the teens to lower 20s will support areas of
elevated fire weather potential.

By Friday, over 80% of ensemble members are advertising some
flavor of a big ridge in the vicinity of the PacNW. Solutions
range from an offshore high pressure center (56% of members) to an
inland-located ridge axis over the forecast area (25% of
members). The unlikely solution (17-19% chance) for Thursday and
Friday is another trough over the PacNW. The latter solution would
result in much cooler temperatures relative to what is forecast.
Moreover, it would support light precipitation for the Cascade
crest and northern Blue Mountains.

Given the favored ridging pattern, little to no precipitation
chances (<10%) exist area-wide through the week. Moreover,
thunderstorm chances are also low (<20%) through the period, and
peak on Monday afternoon across the Blue Mountains.

The anticipated warming trend through the week results in Moderate
HeatRisk forecast for the lower elevations of the Columbia Basin
and Blue Mountain foothills by Friday -- afternoon high
temperatures have a 50-70% chance of exceeding 90 degrees, and a
5-15% chance of exceeding 100 degrees for our main population
centers. Plunkett/86

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  81  55  84  57 /   0   0   0  10
ALW  83  57  87  59 /   0   0   0  10
PSC  85  59  88  62 /   0   0   0  10
YKM  82  57  85  57 /   0   0   0   0
HRI  85  57  88  61 /   0   0   0  10
ELN  80  55  81  55 /   0   0   0  10
RDM  80  50  80  50 /   0   0   0   0
LGD  78  52  83  55 /   0   0   0  20
GCD  81  52  87  53 /   0   0   0  10
DLS  85  59  85  61 /   0   0   0   0

&&

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

$$

SHORT TERM...82
LONG TERM....86
AVIATION...97