Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 261217 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
415 AM PST Sun Feb 26 2017

Updated AVIATION Discussion

.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. 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 jet streak near
5000 feet above MSL, which will produce breezy/windy winds of 20-30
mph Friday afternoon and Friday night into Saturday in the Lower
Columbia Basin and along the Foothills of the Blue Mountains. A
moisture plume associated with the upper level jet stream will keep
a chance for snow in the mountains Friday night and Saturday.  Polan

&&

.AVIATION...12Z TAFs...MVFR conditions will occur at all TAF sites
through as cloud bases lower and snow restricts visibility. The VFR
conditions will persist through the day and into the overnight. Winds
will be less than 10 knots through the period.  Polan

&&

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

&&

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

     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.

&&

$$

79/99/99


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