Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 261746
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
945 AM PST Sun Feb 26 2017

Updated Aviation Discussion

.SHORT TERM...satellite showing well defined upper low just off
the Oregon coast this morning. Enhanced clouds covering most of
the forecast area. Surface observations indicating snow and lower
elevation rain for many locations. The upper low will slowly move
inland later today and tonight. Mixed precipitation will continue
today changing to all snow tonight as temperatures cool back into
the 20s. The mid and higher elevations will receive significant
snowfall through tonight and advisories look good for now. Have
added the John Day highlands this morning as well. Parts of the
Columbia basin will be warm enough today for mixed rain and snow
or just rain. This will keep snow accumulations down especially for
elevations below 1200 feet. Colder temps tonight should allow for
a few inches accumulation.  94

&&

.AVIATION...18Z TAFs. Scattered rain and snow showers in eastern
Washington and northeast Oregon will keep MVFR/IFR conditions
through the day and evening hours then will improve to VFR tonight
as precipitation tapers off.  KALW and KPDT will maintain MVFR or
less through the night with occasional light snow. It will remain
VFR at KRDM and KBDN until mid afternoon then MVFR from around 22Z-
03Z in light rain and snow showers.  South winds 10-15 knots gusting
to 25 knots will continue through the evening at KRDM and KBDN.
Otherwise...winds will be 10 knots or less at the other terminal
airports.  Wister

&&

.PREV DISCUSSION... /issued 700 AM PST Sun Feb 26 2017/

SHORT TERM...Today through Monday night...Will keep Winter
Weather Advisory for snow in place across Cascades, Blues, and
Wallowa Mountains with no additions at this time.  Long period of
light to moderate snow for mainly the mountain areas of the inland
northwest. Satellite shows upper level trof dropping south about 40
mph off the Washington coast.  Short range models in good agreement
in bringing trof across the inland northwest overnight and Monday.
Another short wave trof will move rapidly southeast across the area
Monday night with another shot of snow.  The northwest flow will
favor upslope snow for the Cascades crest and just east and also the
west and northwest facing slopes of the Blues and Wallowa Mountains.

The rest of the area will be more terrain shadowed from significant
precipitation. Snow levels are less than 1K feet, but with
temperatures rising to above freezing during the day in the lower
elevations, this should keep snow accumulations in check for the
most part. Road/soil temperatures have rebounded and with a stronger
sun shining through the clouds, roads in the lower elevations will
be mostly wet or slushy during the day, but likely freeze at night.
Am a little concerned about locales near the Blues from Dayton and
Weston to Pilot Rock, Heppner and Condon which may approach advisory
level snow and will need to watch later for possible advisory
issuance.

LONG TERM...Tuesday through Saturday...Northwest flow aloft will
provide orographic lift and thus a chance of snow showers in the
eastern mountains on Tuesday. Significant westerly component to flow
aloft will yield downslope winds in central and north central Oregon
and in the Kittitas and Yakima Valleys for dry conditions through
the day on Tuesday. The flow aloft slowly backs from northwest to
west Tuesday night through Thursday, which will produce downslope
winds and thus dry conditions at lower elevations Tuesday night
through Thursday afternoon with a chance of snow showers along the
east slopes of the central Washington Cascades and a slight chance
of snow showers in the Northern Blue Mountains through Thursday
afternoon. Thursday night a warm front spreads snow to the Cascades
with the warm front then spreading snow into forecast area during
the day on Friday. Friday a strong upper level 110-125 mph jet
stream centered around 30000 feet moves into the region and brings
with it a low level 50-60 mph jet streak near 5000 feet above MSL,
which will produce breezy/windy conditions of 20-30 mph sustained
surface winds with gusts to 35-45 mph Friday afternoon and Friday
night into Saturday across the Lower Columbia Basin and along the
Foothills of the Blue Mountains of Washington and Oregon. A moisture
plume associated with the upper level jet stream will keep a chance
for rain showers at lower elevations and a chance for snow showers
in the mountains Friday night and Saturday.  Polan

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  38  26  39  25 /  80  70  40  40
ALW  38  27  39  26 /  80  70  50  50
PSC  40  26  40  25 /  70  60  30  30
YKM  38  22  39  21 /  70  60  30  20
HRI  40  26  40  26 /  70  60  30  30
ELN  34  17  34  17 /  80  60  30  30
RDM  36  21  38  21 /  60  60  30  40
LGD  35  24  37  23 /  80  70  50  60
GCD  34  20  37  22 /  70  70  50  50
DLS  39  27  40  28 /  70  60  40  40

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 AM PST Tuesday for ORZ049-050-
     502-503-505-506.

     Winter Weather Advisory until 10 PM PST Monday for ORZ509.

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

     Winter Weather Advisory until 10 PM PST Monday for WAZ520.

&&

$$

94/85


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