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000
FXUS66 KPDT 120406
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
806 PM PST Wed Dec 11 2019

.UPDATE...A weather system was effecting the area with rain and
snow that will persist overnight. Specifically the east slopes of
the Washington cascades along with the kittitas valley is expected
to receive between 2 to 6 inches and a winter weather advisory is
in effect overnight. Elsewhere temperatures remain slightly above
freezing and rain and snow is expected with snow levels remaining
above 4k feet over the eastern mountains. Patchy fog was
continuing over portions of the columbia basin and visibilities
were lowering in some locations under one mile. Changes were done
to wx and pops and snow totals and now the present short term
forecast appears more on track.

&&

.PREV DISCUSSION... /issued 226 PM PST Wed Dec 11 2019/

SHORT TERM...Tonight through Thursday night. The next in a
series of weather disturbances has started to impact the forecast
area this afternoon. A frontal boundary associated with a low
pressure system off the coast is moving across Central OR and WA,
with radar showing snow and rain showers impacting Western and
portions of Central OR and WA at this time. This initial frontal
boundary will bring periods of rain and high elevation snow
through tonight into tomorrow, while a follow up of upper level
disturbances will continue precipitation chances into Friday
before waning into the weekend. A winter weather advisory was
issued for areas above 2000 feet along the eastern slopes of the
WA Cascades, as snow accumulations of 3-6 inches are expected in
the passes. Snow levels will mostly be between 4000-5000 feet
through the period, with snow levels in the Kittitas Valley up to
the East slopes of the WA Cascades between 2500-3000 feet tonight
and rising by Friday afternoon. Ahead of the frontal boundary
earlier today, central OR and Grande Ronde valley winds picked up,
and are expected to stay breezy into Friday. Lawhorn

Friday through Saturday...The strong westerly jet will lower south
and will become positioned just north of 40N on Friday, and the
moist westerly flow will mainly affect the southern half of Oregon.
Although colder air will lower snow levels down to around 3000-3500
feet, most precipitation on Friday will be along the Cascades and
south of Jefferson and Wheeler Counties. The jet will continue to
lower southward Friday night, and any showers remaining will be
isolated to scattered mountain snow showers Friday night and
Saturday with mostly cloudy skies elsewhere.   Wister

LONG TERM...Saturday night through Wednesday. A few showers will
linger over the mountains Saturday night and Sunday in northwest
flow.  A ridge is expected to build along the coast and then move
inland Monday and Tuesday with mainly dry conditions. The next
system to bring a chance of snow showers to the area starting
Wednesday, with most of the system to move through Wednesday night
and Thursday.  Temperatures are expected to be near normal through
the period. 93

AVIATION...00z Tafs. Rain will spread west to east with
snow above 4500 feet overnight. Widespread MVFR and IFR conditions
are expected for most of the period due to low CIGS and VSBYS in
-RA and BR. The rain should decrease to showers after 12-15z with
 conditions improving to VFR at most sites. Winds will be 10-15
 kts and gusty at BDN/RDM with light winds at other sites
 overnight and then increasing to 5-10 kts on Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  39  51  38  46 /  70  50  50  20
ALW  38  50  39  45 /  70  60  60  30
PSC  37  51  38  47 /  60  40  30  10
YKM  32  45  29  46 /  70  50  30  10
HRI  36  52  39  48 /  60  40  30  10
ELN  30  43  30  41 /  70  60  40  10
RDM  35  48  30  44 /  70  70  60  30
LGD  36  47  34  42 /  70  70  60  40
GCD  36  45  33  41 /  80  70  60  30
DLS  37  48  37  47 /  80  70  60  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...Winter Weather Advisory until 4 AM PST Thursday for WAZ520.

     Winter Weather Advisory until 10 AM PST Thursday for WAZ026.

&&

$$

97/