109
FXUS66 KPDT 111114
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
413 AM PDT Sat May 11 2024

Updated aviation discussion

.SHORT TERM...Today through Monday night...Clear skies allowed for
a perfect view of the Auroras this evening as we continue to be
dominated by the upper level ridge. Temperatures today will be
roughly 5 degrees warmer across the forecast area with dry
conditions continuing.

Models show the ridge to continue to strengthen over the forecast
region through today keeping the area dry. EFI shows the majority of
the area to be above climatological normal today with 70-90% of the
raw ensembles showing the Columbia and lower Columbia Basin, Yakima
Valley and portions of the Gorge to be above 85 degrees with some
isolated low 90s. The foothills, central and north central OR will
see the upper 70s to low 80s with isolated mid 80s and the higher
terrains will see the upper 60s.

Sunday and continuing through Monday, models show the upper level
ridge flattening as an upper level shortwave makes its way into the
area. By Monday the shortwave will have moved the ridge eastward and
will bring northwesterly flow back to the region. Even with this
shortwave crossing the area, models and ensembles show this
shortwave to be mostly dry. Ensembles show a less than 20%
probability of light rain over the highest peaks of the WA Cascades.
The main noticeable change that the shortwave will bring is the
cooler temperatures by Monday and increased winds both days. EFI
continues to show the region to be above average temperatures with
80-90% of the raw ensembles showing the entirety of the Basin,
Yakima Valley, and the foothills of the Blues seeing temperatures in
the upper 80s with a few isolated 90s, mid elevations in the upper
70s to low 80s and upper elevations still in the upper 60s. By
Monday the EFI has backed off and modulated towards near normal
temperatures for the majority of the area.  Less than 60% of the raw
ensembles show the Basin in the mid 80s. However, over 80% of the
raw ensembles have the region in the upper 70s to low 80s, mid
elevations in the upper 70s and the higher terrains in the 50s.

Lastly, as the shortwave makes its way across the Cascades, models
show the low level pressure gradients tightening along the Cascades.
This will bring increased winds on Sunday through the Cascade Gaps
with 70% probabilities the Gorge, Simcoe Highlands and both Yakima
and Kittitas Valleys will see sustained winds to 20 mph. By Monday
the models show the gradients tightening even more as the shortwave
passes the Cascades and winds will increase even more. Monday shows
an increase to 80% probabilities the aforementioned areas will see
sustained winds to 25 plus mph with 50-80% probabilities of gusts to
40 mph.

Quick note: If you are outside enjoying the warmth, please be
mindful and wear sunscreen, drink plenty of fluids and remember that
the rivers will be fast flowing and still dangerously cold.
Bennese/90

.LONG TERM...Tuesday through Saturday...Ensemble and deterministic
models start out in showing good agreement with a building ridge
Tuesday following Monday`s trough passage but they continue to
differ from Wednesday onward. However, they are agreeing that the
advertised persistent ridging pattern does not hold and that a
trough over western Canada will become the dominant weather feature
at some point late in the week. Thus timing of said trough remains
in question amongst the models at this point.

ECMWF is fastest at breaking down the ridge by bringing a trough
through western Canada on Wednesday that clips the region. This is
followed by a secondary shortwave that drives the trough further
south over the region late Thursday and Friday. Meanwhile, the GFS
does maintain a flat ridge pattern over the region through the week
but does bring a trough into the region on Friday which closely
matches with the timing and position of the second shortwave in the
ECMWF solution. Both models then drive this trough east and out of
the forecast area on Saturday leaving a verily dry westerly flow
over the forecast area.

So, forecast will reflect the model agreement on Tuesday by being
dry and warm. This will be followed by the effects of a westerly
flow as indicated by a few showers along the Cascade crest Wednesday
through Sunday while mainly dry across the rest of the forecast area
but with a low degree of confidence. NBM high temperature variations
continue to show a large range of due to the model uncertainty but
overall maintaining a little above normal. No model solutions
indicate any significant event through the extended other than some
breezy to windy conditions associated with the trough passage over
the Thursday through Friday period.


&&

.AVIATION...06Z TAFs...Clear skies for all sites for the next
24 hours. Light winds will increase midday with some sustained AOA
10kts and gusts AOA 20kts mainly at DLS, RDM and BDN. Wind decrease
around sunset becoming light again overnight.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  83  54  83  53 /   0   0   0   0
ALW  85  59  85  58 /   0   0   0   0
PSC  91  58  89  57 /   0   0   0   0
YKM  90  51  88  50 /   0   0   0   0
HRI  89  56  88  56 /   0   0   0   0
ELN  86  54  84  52 /   0   0   0   0
RDM  82  47  80  43 /   0   0   0   0
LGD  80  51  80  48 /   0   0   0   0
GCD  80  49  81  46 /   0   0   0   0
DLS  88  58  84  55 /   0   0   0   0

&&

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

$$

SHORT TERM...90
LONG TERM....91
AVIATION...85