453
FXUS66 KPDT 101111 AAA
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
311 AM PST Fri Jan 10 2025

Updated Aviation Discussion

.SHORT TERM...Today through Sunday...

Bottom Line Up Front

1. Mountain snow Friday lingering through Saturday

2. Windy conditions Friday into Saturday morning


Current radar shows the system to still be off the coast of the
PacNW and already beginning to flatten out the ridge overhead.
Looking at current radar, the area is still under dry conditions at
the moment. However, ground observations as well as webcams shows
that there are some lingering areas of fog/freezing fog through
portions of central and north central OR. Will keep the dense fog
advisory in affect for north central OR as central OR has cleared.

Models are in firm agreement with the upper level system pushing its
way onshore and continuing to flatten the ridge. Models also show
that this upper level system will bring with it increased moisture
that will bring precipitation to the mountains. Due to this, a
winter weather advisory has been issued above 4000 feet for the
Northern Blue Mountains. Snow accumulation along the Cascades will
range between 3-4 inches which remains under advisory criteria,
higher along the crests,80-90% of the raw ensembles are in
agreement. Along the Northern Blues, 80-90% of the raw ensembles
show snow accumulations between 6-8 inches. Once the system
passes, models show some lingering mountain snow showers with
little accumulation Saturday.

Surface models show a tightening of the gradients from Ontario to
the Blues which will increase the winds through the Grande Ronde
Valley. With the millibars showing at 10 mb tightening, winds
through the area will reach above 45 mph with over 70% of the raw
ensembles in agreement. However, the ensembles show mainly Ladd and
Pile Canyons being the recipients of the stronger winds while La
Grande will see between 20-25 mph. A wind advisory has been issued
for the aforementioned area from now through 1 PM Friday. By Friday
afternoon, models show the leading edge of the system pushing
onshore with a surface front moving across the Cascades. Again,
looking at the model guidance for pressure gradients across the
region show a 10 mb difference across the Cascades. This will lead
to increased winds along the foothills of the Northern and Southern
Blues with 80-90% of the raw ensembles showing the area seeing 20-30
mph sustained winds with gusts to 50 mph. Therefore a wind advisory
has been issued beginning Friday 4 PM through 1 AM Saturday.
Bennese/90

.LONG TERM...Monday through Friday...Deterministic models and
ensemble clusters are in good agreement on the evolution of the
large scale pattern through the extended period. Overall a quiet
weather is in store with an upper ridge being the dominant weather
feature through Thursday. This will provide a favorable setup for
the typical stratus and fog in the lower elevations. For this
forecast have included the stratus and fog at elevations below 2000
feet MSL. This is supported by ensemble soundings that show surface
based inversions. Given the pattern confidence is high (70-80%) in
this forecast scenario.

On Friday models are depicting a shortwave trough moving either over
or east of the region in northwesterly flow aloft. Ensemble clusters
are favoring a solution of the shortwave moving just to the east of
the forecast area but close enough to produce a chance of light
precipitation in the mountains. NBM POPS were used for this forecast
and they are 15-40% for the mountains for Friday. Snow levels will
be low enough for snow but the threat for heavy amounts appears low
(20%). One caveat however is that the operational ECMWF moves the
shortwave trough farther west directly over Oregon and Washington
and is generating moderate amounts of QPF for the northeast
mountains (.25-.50 inches).

Temperatures will be mostly below normal in the lower elevations
through the period and near to above normal in the mountains. 78


&&

.AVIATION...12Z TAFS...Low stratus and patchy fog are currently
causing MVFR/IFR conditions at TAF sites except KBDN and KRDM which
are both VFR. A cold front will cross the region from NW to SE today
bringing MVFR conditions and a brief period of rain showers.
Conditions will improve to mostly VFR late this afternoon/early
evening behind the front...but winds will increase and gust 20-30kt
especially at KPDT, KDLS, KRDM, and KBDN. 78

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  45  33  43  29 /  80  20   0   0
ALW  43  34  44  31 /  90  40   0   0
PSC  45  35  48  31 /  50  10   0   0
YKM  44  29  47  27 /  40  10   0   0
HRI  48  35  48  32 /  60  10   0   0
ELN  41  33  42  29 /  50  10   0   0
RDM  46  27  40  22 /  60  10   0   0
LGD  41  32  39  26 /  90  70  10   0
GCD  44  28  36  24 /  80  50  10   0
DLS  50  39  48  36 /  80  10   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 1 PM PST this afternoon for ORZ049.

     Winter Weather Advisory from 10 AM this morning to 4 AM PST
     Saturday for ORZ502.

     Wind Advisory from 4 PM this afternoon to 1 AM PST Saturday for
     ORZ507-508.

     Freezing Fog Advisory until 10 AM PST this morning for ORZ510.

WA...Winter Weather Advisory from 10 AM this morning to 4 AM PST
     Saturday for WAZ030.

&&

$$

SHORT TERM...90
LONG TERM....78
AVIATION...78