Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 101234 AAB
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
434 AM PST Sat Dec 10 2016

Updated to remove winter weather advisory for the Blue Mountains

.SHORT TERM...Today through Monday...A weak cold front is currently
moving across the forecast area at this time with areas of snow...or
sleet and freezing rain. The precipitation type is changed to mostly
all snow with the passage of the cold front. As colder air moves in
aloft behind the remainder of the precipitation will change to back
to snow. Little additional accumulation is expected in the lower
elevations but there could be a couple to several more inches of
snow on the Cascade east slopes...especially the WA Cascades. As
such will will leave the warning in place there. Later today and on
Sunday there will be some drying taking place behind this system and
there will be breaks in the overcast for some sunshine and warming.
Increased west to southwest winds will help to scour out the trapped
cold air in the Basin and surrounding valleys/Foothills also
resulting in warming there. The most likely areas to mix out will be
the Blue Mountain Foothills and the Oregon side of the Lower
Columbia Basin where temperatures will warm up to the 30s today and
upper 30s to mid 40s on Sunday. This will cause melting of snow on
the ground. It might stay below freezing north of the Lower Columbia
Basin in the Yakima and Kittitas valley. Monday will be a transition
day with the next modified arctic air intrusion about to arrive to
the region in the extended period. It will be slow to move in and
the real cold temperatures will not be expected until the extended
period. There may be some snow showers on Monday as the cold front
moves into the region...but snow amounts are expected to be very
light. Due to the lessing of precipitation have let the Winter
Weather Advisory for the Blue Mountains expire at 4 AM PST. Will
hold onto the Winter Storm Warning for the Washington Cascade east
slopes and Simcoe Highlands through the day today until 3 pm PST as
a few more inches of snow is likely there. 88

.LONG TERM...Monday night through Saturday...Models have come into
better agreement about an active weather pattern through the long
term period. Initially there will be a large upper low over much of
Canada with a smaller low off the British Columbia coast. A cold
west to northwest flow will keep a chance of light snow in the
mountains and a slight chance of light snow in the lower elevations
though the Washington Columbia Basin should see little if any
precipitation. Tuesday night and Wednesday weak ridging will push a
surge of moisture into the Oregon portion of the area for a
continued chance of snow in the mountains. Temperatures in this
period will remain mainly in the 20s and will turn even colder as
models show an Arctic air mass moving in Thursday and remaining
through Saturday. Temperatures will drop to the mid teens to mid 20s
with lows of around zero to 10 above. This is from the ECMWF
guidance. GFS temperatures are about 6-8 degrees colder than that.
There will continue to be a chance of snow mainly in the mountains
though with a cold and dry air mass, snow amounts will be fairly
low. Perry

&&

.AVIATION...12Z TAFs...Showers are winding down this morning but
light snow showers with MVFR and lower ceilings and visibility
continue at KDLS, KPDT and KALW and are possible at KYKM and KPSC,
perhaps mixed with -FZRA at times. Have kept VCSH at KRDM and KBDN
for a few more hours but they have warmed to above freezing so
would expect light rain there. Precipitation will end by 18Z and dry
weather is expected through this evening. Another weak disturbance
will move through the area tonight and have VCSH at several places
in case any light snow showers develop. Ceilings will be primarily
above 4000 feet agl though KALW may have MVFR ceilings and guidance
is hinting at lower visibility and BR at KYKM after 00Z. Winds will
remain below 15 kts for the next 24 hours aside from 10-20 kt winds
at KBDN and perhaps KRDM this morning. Perry

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  33  30  41  30 /  30  20  40  50
ALW  34  32  42  32 /  30  20  40  60
PSC  34  31  41  30 /  10  10  30  50
YKM  33  25  39  24 /  20  10  30  50
HRI  34  31  42  30 /  10  10  30  50
ELN  32  25  37  24 /  40  20  30  50
RDM  35  26  39  25 /  20  20  50  60
LGD  35  27  37  26 /  40  30  50  60
GCD  36  30  37  29 /  40  20  50  60
DLS  38  33  43  32 /  30  20  60  60

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...none.

WA...Winter Storm Warning until 3 PM PST this afternoon for WAZ520-
     521.

&&

$$

88/83/83


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