Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 201158 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
358 AM PST Sat Jan 20 2018

.SHORT TERM...Today through Monday...An upper trough over the
western U.S. will gradually shift to a westerly onshore flow today.
A weak disturbance moving into the region early this morning will
drift east across the region as the upper flow pattern changes
today. As such will see a fair amount of cloud cover with isolated
to scattered rain and snow showers. The best chances for showers
will be over the mountains. Snow accumulations with the showers will
be light and spotty. These showers will decrease this evening as a
weak upper level ridge drifts across the region. The next Pacific
system will move into and across the region Sunday and Sunday
evening. This system is expected to split, thus decreasing the
amount of precip over southeast Washington, and northeast and
central Oregon. With snow levels still relatively low, should still
see some decent snow at locations above 2-3000 feet. At this time
snow accumulations look to be highest along the Washington Cascade
east slopes with possibly 2-6 inches. Will hold off on highlights
for this area at this time. Elsewhere 2-4 inch amounts are possible
over the Blue mountains and along the Oregon Cascade east slopes.
Winds will also be problem with this system as breezy to windy
conditions will be possible over central Oregon, the Grande Ronde
valley and the Blue mountain foothills. Winds at the south end of
the Grande Ronde valley are expected to run 25 to 35 mph with gusts
of 45 to 50 mph Sunday and Sunday evening. Will issue a wind
advisory for this area. Similar winds may locally occur at the base
of the Blue mountains between Pilot Rock and Walla Walla. For now
will hold off on highlights in this area due to the localized nature
of the event. Onshore flow behind the Sunday system will keep
isolated to scattered showers going over portions of the area late
Sunday night into Monday. 90

.LONG TERM...Monday night through Friday...Models show a ridge of
high pressure over the region Monday night for dry conditions.
The ridge axis moves east into Idaho on Tuesday allowing flow aloft
to back to the SW thus bringing increasing moisture into the
forecast area for a chance of precipitation with snow levels 1500-
2500 feet on Tuesday. A warm front with attendant valley/basin rain
and mountain snow spreads over the region Tuesday night and
Wednesday resulting in snow levels rising to 2000-4000 along the
east slopes of the Washington Cascades and 4000-4500 feet in central
and NE Oregon by Wednesday afternoon. This will be followed by a
cold front Wednesday night and Thursday for snow likely in the Blue
Mountains and rain in the Columbia Basin. Decreasing PoPs on Friday
as a ridge moves over the region.  Polan

&&

.AVIATION...12Z TAFS...VFR conditions will prevail for the next 24
hours. There will be isolated to widely scattered snow showers over
the Blue Mountains today, which will have MVFR ceilings and
visibilities associated with the snow showers. Winds will remain
light today through tonight.   Polan

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  47  32  48  34 /  20  10  80  70
ALW  49  34  50  36 /  20  10  70  70
PSC  49  33  47  35 /  10  10  80  50
YKM  49  30  42  30 /  10  10  50  30
HRI  49  31  47  34 /  10  10  70  50
ELN  44  29  38  28 /  20  10  70  30
RDM  43  28  46  28 /  20  10  40  40
LGD  41  28  39  31 /  30  20  60  80
GCD  41  26  39  30 /  20  10  80  60
DLS  49  34  45  35 /  20  10  70  50

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 7 AM to 10 PM PST Sunday for ORZ049.

WA...None.
&&

$$

90/99/99



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