662
FXUS66 KPDT 102103
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
203 PM PDT Fri May 10 2024

.SHORT TERM...Today through Sunday...Clear skies prevail over the
region as an upper-level ridge remains centered just off the coast
of Oregon. This ridge will allow temps to climb well above average -
as much as 20 degrees in some areas - with highs potentially
eclipsing the 90s over the weekend across the lower Basin and Gorge.
This ridge will flatten out by Sunday as a shortwave arrives and
brings gusty winds to the forecast area. This system has little in
the way of moisture, so outside of a weak orographic shower over the
Cascade crests, expecting a dry forecast for the period. Gap flows
are where we expect the strongest winds Sunday afternoon, namely the
Gorge, Oregon Basin, Kittitas Valley, and Simcoe Highlands. NBM
probabilistic guidance has a low chance (30-40%) of winds reaching
advisory criteria, so expecting more of a typical springtime breezy
day rather than anything truly significant.

Rivers and streams will continue to see rises as mountain snowmelt
accelerates under anomalously warm temps. Naches still looks to be
the only river that will reach bankfull, however should high
pressure build back in next week, more prolonged river rises could
occur. The long term period is very much in the air, however, so
enjoy the pleasant weather while it lasts! Evans/74

.LONG TERM...Monday through Friday...Models in good agreement
through Tuesday, but begin to diverge significantly on their
evolution of an upper level ridge over the eastern Pacific Ocean.
EOFs show a variance of 53+% from Wednesday onward with the WPC
clusters shifting between a dominant ridge and a weak trough or
zonal flow. The ensembles show a similar pattern where GFS wants to
develop an upper level ridge over the eastern Pacific Ocean and
moving it inland but weakening it by Friday while the ECMWF
retrogrades the upper ridge allowing for a more troughy pattern over
the Pacific Northwest. The deterministic models paint a similar
picture with the GFS showing a strong ridge developing over the
eastern Pacific Ocean and moving inland over the weekend while the
ECMWF mimics its ensemble solution. These differences from Wednesday
onward will have significant impacts on temperatures and
precipitation chances. If the GFS solution panes out, it will be hot
and dry with daytime highs approaching 15-20 degrees above normal by
the weekend.  If the ECMWF has the correct solution, it will be near
to below normal with periods of rain. As a result, there is very low
confidence (80-90%) in which solution will pain out so the best
solution is to keep close to NBM which is trending warmer, but not
as warm as the GFS. NBM is drier too which presently is the way to
go until models start settling in on a solution.

With a couple of shortwave troughs moving through the area Monday
into Monday night, we can expected breezy to windy conditions over
the Columbia Basin, especially through the Gorge and the Kittitas
Valley. There may be some afternoon/evening showers over the
mountains too, especially Northeast Oregon. Earle/81

&&

.AVIATION...Previous discussion...18Z TAFs...VFR conditions will
prevail through the period. Skies will be clear with winds below
10 kts. Earle/81

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  51  83  54  83 /   0   0   0   0
ALW  55  86  60  85 /   0   0   0   0
PSC  55  90  58  90 /   0   0   0   0
YKM  52  89  52  88 /   0   0   0   0
HRI  53  89  58  87 /   0   0   0   0
ELN  53  86  54  84 /   0   0   0   0
RDM  46  83  47  80 /   0   0   0   0
LGD  49  80  50  81 /   0   0   0   0
GCD  48  80  49  81 /   0   0   0   0
DLS  57  89  57  84 /   0   0   0   0

&&

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

$$

SHORT TERM...74
LONG TERM....81
AVIATION...81