Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 221754
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
954 AM PST Mon Jan 22 2018

.SHORT TERM...A generally westerly flow aloft remains over the
area this morning. A couple of weak ripples in the flow will keep
scattered light snow showers in the mountains today and a slight
chance of rain showers in the Blue Mountain Foothills. The rest of
the Columbia Basin and Central Oregon should remain dry. Have
adjusted rain and snow chances this morning downward due to the
lack of returns right now on radar. Also reduced cloud cover
somewhat today and lowered temperatures a degree or so as they
looked a little too warm compared to guidance. Otherwise forecast
is in good shape. Main forecast challenge today will be the system
arriving tomorrow into Wednesday. Snow levels will remain low
into Tuesday night before rising due to warm air advection. The
snow levels will be critical to how much snow will fall along the
Cascade crest region Tuesday through Wednesday. May need to issue
a Winter Weather Advisory for the Washington Cascades with the
afternoon forecast package. The Oregon Cascades look like they
will remain below advisory amounts. Forecast update already out.
Perry

&&

.AVIATION...18Z TAFs...VFR conditions should prevail the next 24
hours. However, KDLS may see IFR/MVFR conditions by 23/12Z due to
fog and low clouds. A system will begin to spread precipitation
across the area by sunrise Tuesday. Winds will generally be less
than 12 kts. Earle

&&

.PREV DISCUSSION... /issued 938 AM PST Mon Jan 22 2018/

SHORT TERM...Today through Wednesday...The upper level flow will
continue to be onshore westerly today. A weak disturbance within
this flow will move across the region today. The combination of the
onshore flow and the disturbance will cause isolated to scattered
showers over the area at times. Best chances will be the along the
Cascade east slopes where numerous showers will be possible this
morning. Snow levels this morning range from near 1000 feet to near
3000 feet. Snow levels will rise to between 2500 and 3600 feet this
afternoon. Overall, snow accumulations should be light and spotty
due to the showery nature of the precip. A weak upper level ridge
will build over the region tonight. Thus will see chances of showers
decrease, becoming very limited by midnight. The next Pacific system
will then push precip into the region Tuesday morning, with much of
the area having decent chances through the day. Snow levels will be
low again Tuesday morning, but will gradually rise during the
afternoon and evening. The Washington Cascade east slopes and the
Kittitas valley will see the slowest rise in snow levels, thus these
areas will most likely see snow through the day Tuesday. Could see
up to 2 inches in the Kittitas valley and 2 to 6 inches in the
Washington Cascade east slopes. Winds will become breezy to locally
windy over portions of central Oregon, the Grande Ronde valley and
the Blue mountain foothills on Tuesday. A moist southwest flow will
keep precip chances high late Tuesday night into Wednesday. Snow
levels will continue to rise overnight Tuesday and Wednesday
morning, then fall slightly Wednesday afternoon. 90

LONG TERM...Wednesday night through Sunday...A fast moving
disturbance pushes a cold front across the region Wednesday night
with snow levels lowering to 2000-3000 feet overnight and continuing
lower during the day on Thursday thus decreasing to 1000-2000 feet.
Another disturbance moves into the region Thursday night and Friday
and Friday morning for another round of a mix of rain/snow in the
Columbia Basin and additional snow in the mountains. A warm front
brings valley rain and mountain snow to the region over the weekend.
Polan

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  48  31  46  39 /  20  10  50  70
ALW  48  34  47  41 /  20  10  40  70
PSC  50  32  43  39 /  10  10  60  70
YKM  45  30  40  35 /  10  10  60  70
HRI  49  31  44  38 /  10  10  60  60
ELN  41  27  36  31 /  20  10  80  70
RDM  43  27  45  36 /  10  10  40  60
LGD  43  30  39  37 /  30  20  50  70
GCD  42  27  39  36 /  10  10  60  70
DLS  47  34  42  37 /  20  10  80  80

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

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