Area Forecast Discussion
Issued by NWS Pendleton, OR
FXUS66 KPDT 190544
Area Forecast Discussion
National Weather Service Pendleton OR
945 PM PST Wed Jan 18 2017
Updated Aviation Discussion
.UPDATE...Several forecasting challenges have been faced with the
current upper level trough over the Pacific NW. The biggest
challenge has been the cold air that remains trapped from the East
Slopes of the WA Cascades and across the Columbia Basin and the
Eastern Columbia River Gorge. Warm air has finally arrived to the
Oregon side of the Lower Columbia Basin where temperatures have
suddenly risen into the mid 30s to lower 40s once the wind shifted
to the East-Southeast. The Washington side of the Basin is also
observing gradual warming over the past hour with temperatures
around 30-35. There is a band of precipitation extending from
Wenatchee southeast to La Grande that is currently bringing freezing
rain in the Tri-Cities but this should be short-lived as
temperatures warm and the band lifts northeast in the next couple of
hours. Observations and virtual soundings in the Kittitas and
Yakima Valleys would indicate the depth of the cold air is less than
2000 feet at this time. The hourly temperature forecast tonight
will soon be updated to reflect the slow warming taking place in
these areas. The Ice Storm Warning in effect for the East Slopes of
the WA Cascades...the Kittitas and Yakima Valleys...and the Eastern
Columbia River Gorge looks good but could be removed or downgraded
to a Winter Wx Advisory if the cold air is scoured out.
The current Wind Advisory for the Grande Ronde Valley and the Oregon
Blue Mtn Foothills looks on track. The current pressure gradient
from Ontario-Meacham is about 10mb which is quite strong but not as
strong as earlier today. Gradients will continue to relax overnight.
The Winter Storm Warnings for the eastern mountains will remain in
effect although the biggest threat appears to be the sleet and
freezing rain...but several inches of new snow are possible tonight.
.Aviation...06Z TAFs. The -FZRA reported at KYKM and KPSC should
only last for another hour as the band of precipitation is lifting
north out of the area. Temperatures are around 0C so any additional
ice accumulations should be very light. VFR to MVFR conditions will
prevail for the next 24 hours. South winds at 15-20 knots will
decrease at KALW, KPDT, and KBDN overnight. On Thursday...most
areas will have winds less than 10 knots. Wister
.PREV DISCUSSION... /issued 307 PM PST Wed Jan 18 2017/
SHORT TERM....Tonight through Saturday...For Thursday...a
weakening trough will cross the area. Will keep PoPs likely for
the eastern mtns with a few inches of accumulation possible. Other
areas will experience much less precip coverage than the past few
days...with the lowest elevations mainly dry. Temperatures will be
close to seasonal norms for all areas as the coldest air gets
scoured out. The next through will approach the WA/OR coast Friday
then get stretched out across the Pacific Northwest Saturday.
Expect the greatest coverage of precip across Central OR and the
east slopes of the Cascades where high end chance to likely PoPs
will be used. Will use slight chance to low end chance further
east. Temperatures will cool to slightly below normal...with snow
levels falling from 3500-4500 feet Thursday to 1500-3000 feet
LONG TERM....Saturday Night Through Wednesday...An active
weather pattern will continue through Monday. Multiple disturbances
will rotate around an offshore low into eastern WA and OR Saturday
through Monday. This will keep a chance of rain and snow over the
area. Snow levels will range between 1000 and 2500 feet Saturday and
Sunday, then drop Monday as the low moves inland. Dry northerly flow
will begin Monday night with decreasing pops. A few showers may
linger over the mountains Tuesday. An upper level ridge will develop
offshore that will keep WA and OR dry Wednesday. Patchy freezing fog
may develop near the rivers early Tuesday and increase in coverage
.PRELIMINARY POINT TEMPS/POPS...
PDT 37 44 27 38 / 60 40 20 20
ALW 36 46 31 40 / 60 40 10 20
PSC 33 41 24 36 / 50 30 10 20
YKM 32 40 22 36 / 60 20 20 50
HRI 30 40 25 36 / 50 30 10 30
ELN 28 38 22 34 / 60 30 30 50
RDM 35 40 22 37 / 30 20 10 40
LGD 33 37 26 34 / 60 60 10 30
GCD 32 40 25 36 / 60 40 10 40
DLS 32 41 32 37 / 70 30 20 50
OR...Ice Storm Warning until 6 AM PST Thursday for ORZ041.
Winter Storm Warning until noon PST Thursday for ORZ050-502-503.
Winter Storm Warning until 6 AM PST Thursday for ORZ506.
Wind Advisory until 10 PM PST this evening for ORZ507.
Wind Advisory until 4 AM PST Thursday for ORZ049.
Blizzard Warning until noon PST Thursday for ORZ049.
WA...Ice Storm Warning until 6 AM PST Thursday for WAZ024-520.
Winter Storm Warning until noon PST Thursday for WAZ030.
Ice Storm Warning until midnight PST tonight for WAZ026-027-521.