892
FXUS66 KPDT 052259
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
259 PM PST Wed Feb 5 2025

.SHORT TERM...Tonight through Friday...A series of shortwaves and
frontal systems will impact the region through Friday. Satellite
imagery shows the first of these systems already approaching the
forecast area, with increasing mid to upper level cloud cover
spreading east. Meanwhile, surface observations show light snow
making it to the surface across portions of central OR, with
flurries in the Kittitas and Yakima valleys.

Tonight through early tomorrow morning, the region will continue
to see impacts from the incoming shortwave/front passage. Less
than an inch of snow is expected across portions of the Kittitas
and Yakima valleys, as well as in lowland areas outside the
Columbia Basin. In most mountain locations, snow accumulations
will be less than 3 inches (80-90% confidence). However, snow
accumulations between 4 to 8 inches are expected along the OR
Cascade crest, impacting Santiam Pass. Thursday morning, there
will be a brief lull in precipitation across the area as the
shortwave exits to our east.

Beginning Thursday afternoon, snow chances will increase from the
south as a frontal boundary pushes north from Northern CA/Southern
OR. While this pattern would usually result in some warm air
advection and rising snow levels, a northerly flow up to 850mb
will keep a pushing a colder airmass into central OR, limiting
snow levels to 2kft to 2.5kft. Further north, snow levels will
remain at or below the surface. The frontal boundary will continue
to push northeast along the backside of the Blues, resulting in
precipitation chances falling off while an upper level shortwave
trough slides east across OR. This will increase snow chances
across much of OR, with chances falling off fairly quickly north
of the Simcoe Highlands and Horse Heaven Hills. 2 to 4 inches of
snow accumulations are expected across central/north central OR,
OR Blue Mountain foothills, Walla Walla Valley up to Dayton,
Grande Ronde Valley, John Day Basin, and Wallowa valley
(confidence 70-80%). Outside of the Wallowa valley, winter weather
advisories have been issued covering Thursday evening through
Friday afternoon. Across the Blues, OR Cascade crest, and the
Ochoco John Day Highlands expect 3 to 6 inches of snow
accumulations(confidence 75-90%). Elsewhere, snow accumulations
are expected to be generally less than 1 to 2 inches, including
the WA Cascade crest and Simcoe Highlands(confidence 70-80%).

Otherwise, cold conditions will continue into the weekend as
afternoon highs will struggle to warm in the mid to upper 30s in
the lower elevations and mid to upper 20s mountains. Morning lows
will generally be in the teens to low 20s, with potentially single
digits in high elevation and high desert valleys if skies clear in
the overnight hours. Lawhorn/82


.LONG TERM...Saturday to Wednesday...

1) Light snow chances area wide prevail.
2) Extreme cooling trend going through next week.

Guidance is in good agreement that a W/WNW flow aloft will kick off
the extended period, along with high chances of mountain snow (60-
80%) and slight chances (20-40%) along parts of the lower Columbia
Basin and Foothills of the Blues. Moisture is not expected to be
abundant with this system, with only 1-3 inches expected for higher
elevations and around a trace in the lower lands. This pattern will
persist through the extended with some slight chances of light snow
with very low precip amounts through the Columbia Basin and mountain
ridges.

Temperatures will continue a cooling trend going in Tuesday as the
NW/N flow a loft continues bringing in cooler/drier air into the
region. Guidance isn`t locked in how low temps will drop in the long
term, but the coolest day will be Tuesday going into early Wednesday
morning with highs and lows -15 to -25 degrees below normal. NBM is
forecasting low to upper teens in parts of the Columbia Basin &
single digits to just below zero in mountain areas, central OR, and
John Day Highlands. NBM probabilistics for the Foothills of the
Blues and central OR has a 20-40% of low temperatures dropping
below zero degrees early Wednesday morning, while chances in the
mountain valleys go up to 50-70%. Probabilistics for less than 10
degrees increase to 60-80% for much of the Foothills of the Blues
& 30-50% for much of the Columbia Basin. /95


&&

.AVIATION...00z TAFs...Latest radar shows some broken showers in the
area, impacting mainly the foothills of the Cascades, with some
lighter activity over the Basin. MVFR cigs are observed at some
sites, namely YKM and DLS, with the expectation that cigs will
remain in the 2-7 kft range for most of the evening, before
relenting overnight. Beyond 04z, dry conditions will prevail, with
all sites expected to be VFR with sct-bkn mid-level cigs and light
winds shifting more north by Thursday afternoon. Evans/74


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  21  32  20  31 /  20  20  50  60
ALW  22  33  22  31 /  30  20  40  60
PSC  22  35  24  38 /  20  10  20  30
YKM  16  33  18  39 /  20  20  20  10
HRI  23  34  23  36 /  20  20  40  40
ELN  13  30  14  36 /  30  10  10   0
RDM  18  33  16  32 /  30  20  50  30
LGD  18  35  21  31 /  60  20  70  80
GCD  19  37  23  32 /  40  30  80  80
DLS  26  36  26  41 /  50  30  30  30

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 7 PM Thursday to 4 PM PST Friday
     for ORZ049-507-508.

     Winter Weather Advisory from 4 PM Thursday to 1 PM PST Friday
     for ORZ505-506-510-511.

     Winter Weather Advisory until 4 AM PST Thursday for ORZ509.

WA...Winter Weather Advisory from 7 PM Thursday to 4 PM PST Friday
     for WAZ029.

&&

$$

SHORT TERM...82
LONG TERM....95
AVIATION...74