114
FXUS66 KPDT 121146
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
446 AM PDT Wed Mar 12 2025

.Updated for Aviation


SHORT TERM...This Morning through Friday Morning...

Key Messages:

1) Winter Weather Advisory in-effect for Oregon Cascades
2) Dry break into Thursday for majority of area
3) Active weather resumes over the weekend.

Radar Indicates showers over the Foothills of the Blues, Cascades,
and Central OR. This band of precip will move NE into the WA/ID area
before a more robust and widespread system pushes through late
Wednesday morning into the afternoon.

Synoptically, a trough just offshore of the Pacific will deepen and
push through the CWA. A cold front will be accompanied with the
system Wednesday afternoon going into the evening. Mountain snow
along with low-elevation rain, with the occasional chance of
thunder, will be associated with this system. NBM not showing
excessive amounts of rain fall for the lower-elevation, with only
scattered parts receiving 20-40% probabilities for 0.3 inches or
less. The main concern will be the mountain snow as the Winter Storm
Advisory will kick in effect for the Oregon Cascades at 5PM
Wednesday until 11PM Thursday. Current forecasts for the Cascade
Crest is between 4-8 inches of precip. Breezy to locally gusty areas
(25-35 mph) will develop Wednesday afternoon across portions of
Central OR and the Columbia Basin. Chances of reaching Wind Advisory
criteria is 25-45% across the Basin/Central OR.

Upper air patterns late Thursday night/early Friday morning depicts
a more zonal/westward flow, decreasing PoPs for the majority of the
area/Columbia Basin. Precip will be mostly limited to the higher
elevations, adding an additional 1-3 inches of mountain snow during
the zonal phase of the system. Active weather returns not long after
later in the day Friday as ensemble guidance is in good agreement
for a secondary shortwave trough to emerge in the Friday
afternoon/evening timeframe. Snow levels drop 2600 feet to 3000
feet, with the heaviest snow in the Cascades, along with lighter
snow around the Central OR region. Clusters are a bit in
disagreement with the troughs amplitude for this system, with 55%
members showing a more deeper trough. These solutions will result in
heavier mountain snow, while the other 45% show the opposite of less
mountain snow and a weaker trough.

LONG TERM...Saturday through Tuesday...A trough will move
onshore Saturday and bring another round of precipitation through
Saturday night and into Sunday. The flow will become southwesterly
into Sunday and bring some decent moisture in, especially for the
Cascades. Precipitation will linger in the mountains on Monday as
another trough moves over the Pacific Northwest, while the lower
elevation dry out. By Tuesday, a ridge should build over the area,
allowing for drier conditions to return most everywhere.

Snow levels will be below 3000 feet to start on Saturday, but will
rise to between 3000 and 4000 feet by afternoon.  Saturday night
will see rises even further.  With the exception of the Washington
Cascades which will remain around 3000 feet, most other areas will
rise to between 4000 and 5000-feet.  Snow levels between 5000 and
5500 feet are forecast for Sunday afternoon, with the Washington
Cascades in the 3000-3500 foot range.

QPF amounts will range from around an inch in the Cascades to around
0.75 inches in the Blues and eastern Oregon Mountains to generally
less than 0.25 inches in the lower elevations and only a few
hundredths in the Columbia Basin and Yakima Valley.  Snow amounts
across the Cascades will likely be 8 inches plus and around 8 inches
plus across the crest of the northern Blue Mountains, into Saturday.

QPF amounts later Saturday into Sunday are higher...Over an inch in
the Cascades and Blues and Wallowas, over 0.25 inches in central
Oregon and around 0.25 inches in some of the lower elevations. Though
portions of the Basin will still receive 0.10 inches or less.
However, with higher and rising snow levels, snow amounts will be
less.

It is likely that either advisories or warnings will be needed for
the Cascades and Blues at some point either Friday through Saturday
or Sunday on later shifts.

It will be breezy to windy both Saturday and Sunday.  Wind gusts on
Saturday across a broad area will be in the 25 to 35 mph range with
some of the normally windier areas, such as the Columbia Basin
reaching 40 mph.  NBM probabilities of wind gusts >= 39 mph are 70
to 90 percent across the Columbia Basin, portions of the Blue
Mountain Foothills, the Simcoe Highlands on Saturday.  NBM
probabilities of wind gusts >= 47 mph are 50 to 80 percent in these
same areas. Similar numbers are evident on Sunday.

By the end of the extended period, there are some big differences
with respect to a trough moving into the west coast, with the
deterministic ECMWF being much deeper, and therefore less
progressive.  THe ECMWF solution is favored in the ensemble clusters
by a few percentage points on both Monday and Tuesday 32% to 30% on
Monday and 36% to 28% on Tuesday.

AVIATION...
12Z TAFS...The latest radar was showing -RA over DLS and PDT/ALW.

Expect more rain to overspread the area during the course of the
day and into tonight. MVFR conditions are being forecast at
DLS/BDN/RDM and YKM with RDM and BDN already experiencing some
MVFR earlier. The rest of the sites could still experience MVFR if
RA gets heavy enough but for now will continue a VFR forecast.

Winds will generally be 10 kts or less, except at BDN and RDM,
where gusts to around 20 kts are expected from this afternoon
through early evening. It is also possible to have some local
gusts with a passing heavy shower just about anywhere.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  59  38  51  30 /  90  50  50  20
ALW  57  39  50  32 /  90  70  60  30
PSC  60  39  56  30 /  80  70  10  10
YKM  53  36  51  27 /  60  80  10  10
HRI  60  38  54  29 /  80  60  30  10
ELN  51  34  48  26 /  60  90  30  20
RDM  53  29  46  24 /  80  60  30  20
LGD  51  35  45  24 /  90  80  70  40
GCD  51  32  43  23 / 100  80  80  30
DLS  53  37  52  32 / 100  90  60  30

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 5 PM this afternoon to 11 PM PDT
     Thursday for ORZ509.

WA...None.
&&

$$

SHORT TERM...95
LONG TERM....77
AVIATION...77