Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 271746
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
945 AM PST Mon Feb 27 2017

Updated Aviation Discussion

.UPDATE...An upper trough remains over the region this morning.
One wave with a band of snow has just about left the area and
moved into Idaho. A westerly flow is continuing light snow showers
into the Blue Mountains from Ukiah northward and expect that will
continue and get stronger through the day. Radar is showing
additional snow showers along the Cascade Crest. Webcams show some
snow cover on I-90 and other highways through the Cascades. Have
made some adjustments to the pops to show less precipitation this
morning in the lower elevations. Also made some minor adjustments
in general for this afternoon. Will keep current Winter Weather
Advisories though the snow amounts in the Grande Ronde Valley and
Wallowa County may be less than previously thought. Previous
forecast is generally in good shape. Dropped temperatures a degree
or so in the Columbia Basin today. Also nudged wind down
slightly. Forecast update already out. Perry

&&

.AVIATION...18Z TAFs.  Conditions are improving this morning for the
areas that were under stratus and snow showers earlier
today...namely KPDT, KALW, KPSC and KYKM.  These areas will
gradually improve to VFR in the next few hours but only for a short
period of time at KALW and KPDT. Another wave diving southeast this
afternoon and evening will bring another round of light snow with a
likelihood of MVFR and IFR conditions at KALW and IFR/LIFR at KPDT.
South to southwest winds will be 5-15 knots with local gusts to 20
knots. Northwest winds will increase to 10-15 gusting to 20 knots at
KDLS tonight. Wister

&&

.PREV DISCUSSION... /issued 356 AM PST Mon Feb 27 2017/

SHORT TERM...Today through Wednesday night...An upper trough is
moving across the eastern mountains this morning with a small band
of snow associated with it. This band produced moderate snow at the
Pendleton Forecast Office and snow amounts if 1 to 2 inches around
midnight. Overall the precipitation will be on the decline this
morning. Snow showers will increase again this afternoon especially
over the mountains as another system dives sewd in the n-nwly flow
aloft. Snow levels will be 1-2 thousand feet this afternoon and down
to the valley floors tonight. Snow amounts will not be particularly
heavy and will drop the Winter Weather Advisories for all areas
expect the northern Blues...Grande Ronde Valley and Wallowa County
with this forecast package. These areas area are along the track of
the upper system and in the case of the Blues will have favorable
upslope flow. Snow showers will diminish slowly on Tuesday but there
will continue to be chance pops over the mountains through the day.
Aside from a few snow showers along the cascade crest and northeast
mountains Tuesday night through Wednesday night conditions will be
dry under partly to mostly cloudy skies. Westerly pressure gradients
will tighten Tuesday night through Wednesday afternoon resulting in
at least breezy to locally windy conditions across the Columbia
Basin and adjacent foothills. Temperatures will moderate through the
period with highs reaching the mid 40s to lower 50s lower elevations
by Wednesday Afternoon 78

LONG TERM...Thursday through Sunday...Westerly flow aloft on
Thursday will yield dry conditions over most of the forecast area,
except for a chance of slop over snow showers along the east slopes
of the Washington Cascades and a chance of orographic snow showers
in the Northern Blue Mountains. Thursday night a warm front spreads
snow showers to the Cascades with the warm front then spreading snow
across the forecast area during the day on Friday. Thursday night a
low level jet streak with winds of 45-60 mph moves over the Lower
Columbia Basin and the Foothills of the Blue Mountains. The higher
winds aloft may mix down to the surface at times Thursday night and
Friday. The low level jet streak is associated with a strong 110-125
mph upper level jet stream around 30000 feet that moves into the
region. The low level jet streak will be around 5000 feet above MSL,
which will produce breezy/windy conditions of 20-30 mph sustained
surface winds with gusts to 35-45 mph Thursday night through 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.
Sunday a strong mid/upper level trough moves inland spreading a
chance of rain showers across the Columbia Basin and snow showers
over the mountains. Polan

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  39  27  43  33 /  50  50  20  10
ALW  40  30  44  36 /  60  60  20  20
PSC  43  27  47  35 /  20  40  10  10
YKM  39  22  44  26 /  30  30  10  10
HRI  42  27  46  33 /  30  30  10  10
ELN  35  19  39  27 /  60  50  10  20
RDM  36  22  40  22 /  40  30  20  10
LGD  36  25  38  28 /  70  60  30  20
GCD  34  24  37  20 /  60  70  40  20
DLS  43  31  47  36 /  40  40  20  20

&&

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

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

&&

$$

83/85/85


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