Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 092232
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
232 PM PST Fri Dec 9 2016

.SHORT TERM...Tonight through Sunday. A moist southwest flow aloft
is present over Oregon and southeast Washington at this time...while
the northern half of Washington is under a westerly flow.  The upper
level flow has played an important role in where the warm air aloft
resides.  Looking at observations across the area and using Dual-Pol
from WSR-88...the warm air appears to be above 5500 feet in far
southeast Washington and northeast Oregon and above 3500-4000 feet
in Central Oregon.  Once the westerly flow increases farther south
and a weak W-E oriented cold front sags southward and lowers
thickness levels tonight...the deep cold air will return with
freezing precipitation returning back to snow. Reports of snow,
sleet and freezing rain were gathered across the Lower Columbia
Basin and the Blue Mtn Foothills this afternoon and a Winter Weather
Advisory was issued for these areas until 6 PM this evening.  The
advisory also included the Grande Ronde Valley and Wallowa
County...although no reports of sleet or snow have been reported so
far.  It`s amazing the difference in the depth of the cold air at
the surface. For example, it is currently 40 degrees at Bend
(elevation 3500 feet) and 27 at Redmond (3000 feet)--two locations
only 14 miles apart with 500 feet difference in elevation.

The cold front tonight will bring an additional 2-5 inches of snow
along the East Slopes of the WA Cascades currently under a Winter
Storm Warning for heavy snow and an additional 1-3 inches over the
Blue Mountains currently under a Winter Weather Advisory. Up to 2
inches of snow can be expected elsewhere.  Again...this is a weak
cold front and a westerly flow aloft will result in rain shadowing
for areas east of the Cascades and the Blue Mountains. Precipitation
will taper off to scattered mountain snow showers Saturday afternoon
and Saturday night. On Sunday...the flow will become more W-NW.
Meanwhile...a southwest surface gradient will tighten with
increasing winds throughout the Columbia Basin down to Central
Oregon.  No wind highlights are anticipated but the amount of mixing
will allow temperatures to climb into the mid 30s to lower 40s in
these areas. Snow levels will be above 2500 feet with several inches
of snow possible in the mountains.  Wister

.LONG TERM...Sunday night through Friday. An active weather pattern
with multiple weather systems to move across the region during the
beginning of the work week. Clouds and snow showers are expected to
persist both Monday and Tuesday and then drier and much colder air
invades from the north on Wednesday. The european model was less
aggressive while the more favorable gfs soln plunges bitter cold air
into our region during the middle of the work week. Overnight temps
could fall below zero. Drier air should continue into Friday while
snow showers are expected to linger over our southern portions of
the region and the area mountains.

&&

.AVIATION...A storm system will bring a mix of winter precipitation
to the area that will create areas of mvfr and ifr conditions across
all taf sites through the period. Ceilings will drop below 1000 feet
at times and vsby could fall below one mile in snow...freezing
rain...and ice pellets.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  25  35  30  39 /  80  20  20  40
ALW  29  36  32  40 /  80  30  20  40
PSC  27  36  31  39 /  60  10  10  30
YKM  20  35  25  37 /  60  20  10  30
HRI  27  36  31  40 /  70  10  10  30
ELN  21  34  25  35 /  70  20  20  30
RDM  26  37  26  37 /  80  10  20  50
LGD  32  37  27  35 /  90  40  30  50
GCD  36  38  30  35 /  80  20  20  50
DLS  31  40  33  41 /  80  40  10  60

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 AM PST Saturday for ORZ502-503.

     Winter Weather Advisory until 6 PM PST this evening for ORZ044-
     049-050-507-508.

WA...Winter Weather Advisory until 4 AM PST Saturday for WAZ030.

     Winter Weather Advisory until 6 PM PST this evening for WAZ028-
     029.

     Winter Storm Warning until 3 PM PST Saturday for WAZ520-521.

&&

$$

85/97/97



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