High Wind in Oregon, December 19, 2017

Area Forecast Discussion
National Weather Service Pendleton OR
400 AM PST Tue Dec 19 2017

.SHORT TERM...Today through Thursday night...There is a continues
feed of moisture riding up over a flat ridge over the west coast.
This moisture is moving down and affecting mainly the northern zones
in the CWA (the Washington zones). Snow levels are rather high...at
about 5000-6000 feet so precipitation type is primarily rain at this
time and is expected to remain so through today. Tonight and
Wednesday a cold front will move across the region with a large
upper trough and cause snow levels to lower to around 1500-2000 feet
on Wednesday. This will cause the precip type to become mainly snow
in the mountains. However by the time the colder air arrives most of
the precipitation will have moved to the east of the CWA with only
showers remaining over the mountains. There could be enough for a
Winter Weather Advisory in the mountains but for now will not issue
any highlights due to uncertainty in the amount of snow that will
accumulate in the mountains. However the day shift will need to re-
analyze to determine if an advisory will be needed. Winds will be
fairly gusty today...especially along the Cascade east slopes which
will cause downslope drying. Winds will also be strong over the
southern Grande Ronde Valley where a wind advisory is currently in
effect until 10 PM this evening. The peak gradients between Meacham
and Ontario will be earlier than that, but it should remain windy
enough to warrant the advisory until 10 PM for the Grande Ronde
Valley. Colder air will continue to move in on Thursday and Thursday
night with just some upslope snow showers over the eastern and
northeast mountains with light accumulations. There will also be
some spill over snow showers over the crest and higher slopes of the
Cascade east slopes. The colder air will be reinforced in the
extended forecast. 88

.LONG TERM...Friday through Christmas Day...A mid/upper level trough
moves southward from British Columbia Friday and pushes a cold front
into the Pacific Northwest. This system exits south of forecast area
Friday night. The ECMWF exhibits more amplitude and thus greater
forcing/dynamic lift with the trough than does the GFS and Canadian
models. Continued to go with a blend of the ECMWF/GFS for Friday
through Friday night. Good chance of snow in the eastern mountains
with this system. Snow accumulations of 4-7 inches expected in the
northern Blue Mountains and the Wallowa Mountains through Friday
evening when snow showers over the Blue and Wallowa Mountains taper
off and end before midnight. A drier and colder airmass moves out of
Canada into the region over the weekend thus a cooling trend over
the weekend and Christmas Day resulting in below normal daytime high
temperatures in the lower to mid 20s.  Polan

&&

.AVIATION...12Z TAFs...VFR conditions will generally prevail for
the next 24 hours, with mid deck BKN/OVC expected across most areas.
Local MVFR conditions will be possible in/near areas of rain. Winds
of 15G26kt this afternoon will lessen by 03-06Z to 12 KT or less,
increasing once again by Tuesday afternoon to 15G25kt.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  52  33  40  23 /  60  70  30  10
ALW  54  35  41  24 /  70  60  30  10
PSC  54  35  44  24 /  60  20  10   0
YKM  49  30  40  20 /  40  20  10   0
HRI  54  34  43  23 /  40  30  20   0
ELN  44  29  37  18 /  60  20  10   0
RDM  51  22  35  12 /  40  80  40   0
LGD  41  28  34  19 /  40  80  40  20
GCD  42  29  35  19 /  20  70  40  20
DLS  54  36  47  26 /  70  50  30   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 8 AM this morning to 10 PM PST this evening
     for ORZ049.

WA...None.

&&

88/99/99