501
FXUS66 KPDT 271118
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
418 AM PDT Thu Jun 27 2024

Updated Aviation Discussion

.SHORT TERM...Today through Saturday...Sensible weather concerns
should be limited during the short term thanks to a transitory
weather pattern with breezy and seasonably cool conditions today
followed by a steady warm up through the beginning of the weekend.
Ensemble guidance is in good agreement on the overall pattern,
showing an upper low over the borders of Washington and Canada
currently progressing eastwards today, followed by a quick
transitory ridge taking its place Friday through early Saturday
before another low approaches the Canadian coastline, with a cold
front and attendant trough beginning to enter our region early
Sunday.

With this pattern, expect another breezy day today as the pressure
gradients remain tightened thanks to the passing system and post-
frontal environment. Peak wind gust chances reaching or exceeding
45 mph over the next 24 hours are around 30-60% outside of the
high terrain near the Kittitas Valley and Simcoe Highlands. This
suggest we should see widespread gusts 25-35 mph today, with
breezes locally reaching 40-45 mph but remaining isolated enough
that wind products will not be warranted. Temperatures are also
notably cooler today, with Spring-like highs for the entirety of
the area. In fact, the NBM only shows probabilities of reaching or
exceeding 80 degrees today for Hermiston up through the Columbia
Basin, with around a 30-60% probability. This means the majority
of the high temperatures for our population centers should run in
the low to upper 70`s, with locations such as Tri-Cities and
Hanford right around 80. Finally, lingering showers are noted
across the eastern mountains of Oregon as well as across the
Cascades. Precipitation should taper off for the eastern mountains
through this morning, but continue across the crests of the
Cascades through this afternoon, exiting by the evening hours.

Under a transitory ridge, conditions then calm tomorrow through
Saturday morning. Temperatures rise around 2-6 degrees Friday and
again on Saturday, placing us near or slightly below normal
and then a few degrees above by Saturday. Otherwise sensible
weather concerns should be mostly nil with calm conditions on
Friday and a few mountain showers beginning overnight Saturday
into Sunday with the approach of the next trough and cold front,
and breezy winds around 20-30 mph through the Cascade Gaps during
the evening and overnight timeframe as well. Goatley/87

.LONG TERM...Sunday through Thursday...The main sensible weather
concerns through the extended forecast will revolve around breezy
to locally windy conditions during and post a trough passage
Sunday and Monday. Otherwise, the remainder of the period looks to
see near seasonable temperatures with little precipitation and
locally breezy conditions.

Ensemble guidance starts in good agreement with an upper trough
and attendant surface cold front pushing across the PacNW Sunday
through early Monday. The cold front passage Sunday will bring
increased winds across the forecast area, which will continue
through Monday as a tightened cross Cascade pressure gradient
persists. Chances for the peak wind gust to meet or exceed 45mph
in a 24hr period are between 60-80% for areas of the Simcoe
Highlands, Kittitas valley, Cascade gaps, southern Blue mountain
foothills, and the OR Columbia Basin for both Sunday and Monday.
The increased winds combined with dry conditions will result in
elevated fire weather concerns both days. Otherwise, the trough
and cold front passage will bring isolated to scattered showers
across the WA Cascade crest, northern Blues, and the Wallowas
Sunday into early Monday. Increasing instability with modest low
level lapse rates across Wallowa county will also facilitate the
development of isolated thunderstorms Sunday afternoon and
evening (chance 15-20%).

Behind the upper trough, there is generally good agreement between
ensemble solutions for ridging to develop upstream in the
northeast Pacific through early Tuesday. However, late Tuesday and
beyond, ensembles come in to disagreement with solutions ranging
from ridging amplifying offshore with northwest flow aloft (ECMWF
ensemble) to a broad shallow trough centered along the northern
Rockies (GFS ensemble). Impact-wise, the difference in the
solutions will mean either a quicker warming period through the
midweek (ECMWF ensemble), or slower warming period through the
midweek (GFS ensemble). As of the most recent NBM run, chances of
hitting or exceeding 90 degrees across the Basin and Yakima valley
Wednesday is only 30-45%, and only 40-55% on Thursday. Confidence
in going temperature forecast at this time is only low-
moderate (25-40%). Meanwhile, either solution will result in dry
conditions settling back across the region with locally breezy
winds through the Cascade gaps in the afternoons (confidence 60%).
Lawhorn/82

.AVIATION...12Z TAFs...VFR conditions to prevail through the
period. Light winds have developed at sites RDM/BDN/YKM, with
winds of 12-15kts at all other sites through the morning. Winds
will increase again through the morning to 12-20kts with gusts up
to 30kts through the afternoon and early evening. Light winds will
develop late this evening at all sites. SCT-BKN mid to high level
cloud decks will diminish through the day, with clear skies
developing overnight. Lawhorn/82

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  73  48  80  54 /   0   0   0   0
ALW  77  52  84  57 /  10  10   0   0
PSC  80  53  84  60 /  10  10   0   0
YKM  76  47  82  55 /   0   0   0   0
HRI  78  51  85  56 /   0   0   0   0
ELN  70  49  81  55 /  10  10   0   0
RDM  73  41  80  48 /   0   0   0   0
LGD  70  45  78  52 /  10  10   0   0
GCD  73  45  81  51 /   0   0   0   0
DLS  74  52  84  58 /  10   0   0   0

&&

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

$$

SHORT TERM...87
LONG TERM....82
AVIATION...82