Area Forecast Discussion
Issued by NWS Pendleton, OR

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152
FXUS66 KPDT 181748 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
948 AM PST Wed Jan 18 2017

Updated Aviation Discussion

.UPDATE...
A brief decrease in precip coverage is being experienced this
morning in between waves rotating around a deep trough of low
pressure just offshore the OR coast. Think precip will increase
somewhat this afternoon as the next wave crosses the area. The
major challenge continues to be the scouring out of the arctic
airmass across the lowest elevations. Some progress at the
scouring out continues across the Blue mountain foothills as
PDT/ALW have risen well into the 40s...while most Basin and
other lowland locations to the west remain in the 20s. With
additional precip likely...have extended the ice storm warnings
and winter weather advisories through this aftn. Still some
question whether the basin/gorge will warm above freezing
today...and will have to monitor precip coverage and temperature
for additional extensions to warnings/advisories through tonight.
Will keep all other warnings/advisories as is for now...with recent
reports of near white out conditions near LaGrande.

&&

.AVIATION...18z tafs...Mainly VFR this morning but brief MVFR
probable near isolated showers. mvfr conditions will prevail for
KYKM, KPSC, KPDT, KDLS, KALW through 18z and then gradually improve.
Fzra still possible at KYKM and KPSC though 0Z. 76

&&

.PREV DISCUSSION... /issued 313 AM PST Wed Jan 18 2017/

SHORT TERM...Today through Thursday night...The latest Pacific
system continues to move into and through Pacific Northwest. The
system`s warm front and associated precip is now affecting Union and
Wallowa counties only. This warm front should exit the area within
the next couple of hours. A secondary disturbance is moving through
western Oregon and Washington at the moment, and should move through
the region during the morning period. Will still see freezing rain
at areas in the basin below around 1800 feet over in the east and
below around 2500 feet in the west. Thus the various advisories and
warnings for ice and sleet will continue across the basin this
morning. Precip across the basin looks to be on track to decrease by
noon. Precip will continue over the higher terrain into tonight.
Snow levels will lower late today through tonight. Thus the threat
of freezing precip in the mountain zones will end as snow becomes
the main precip type. Winds in the Grande Ronde valley remain quite
strong and may have to extend the warning beyond 7 AM. Elsewhere
local winds around 30 mph sustained should persist along the base of
the northern Blue mountains in Umatilla county. Will have to watch
for the potential of an advisory in this area. Still expect the warm
air to mix into the Basin and eventually into the Yakima and
Kittitas valleys, as well as the Gorge this afternoon, but will have
to keep some mention of light freezing rain in these areas. Should
see precip chances continue to decrease late tonight through
Thursday evening. Snow levels will gradually fall through this
period as well. 90

LONG TERM...Friday through Wednesday...GFS/EC models in agreement
with active pattern through the weekend and then drier northerly
flow followed by ridge of high pressure for Tuesday and Wednesday.
Negative tilt trof will rotate multiple disturbances across the
inland northwest Friday through Monday. Precipitation will be
likely in most areas of central oregon. Snow levels will range
between 1500 and 2500 feet and then drop Monday as a colder
northerly flow returns. By this time, however, the trof will have
moved east and the northerly flow will be drier. Look for
temperatures to be near seasonal normal through Monday and then 5
to 10 degrees below normal for Tuesday and Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  34  42  29 /  70  70  30  10
ALW  44  35  42  31 /  80  80  40  10
PSC  38  33  41  29 /  60  60  10  10
YKM  37  28  41  25 /  60  50  10  10
HRI  39  33  42  28 /  60  60  20  10
ELN  34  27  39  26 /  70  60  10  20
RDM  47  29  41  24 /  60  50  20  20
LGD  37  31  40  28 / 100  80  60  20
GCD  44  34  42  24 / 100  60  50  20
DLS  39  33  43  31 /  70  70  30  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 PM PST this afternoon for
ORZ507-     508-510.

     Ice Storm Warning until 6 PM PST this evening for ORZ041.

     Winter Storm Warning until noon PST Thursday for ORZ502-503.

     Winter Storm Warning until 4 PM PST Thursday for ORZ050.

     Winter Storm Warning until 6 AM PST Thursday for ORZ506.

     Wind Advisory until 10 PM PST this evening for ORZ507.

     High Wind Warning until 6 PM PST this evening for ORZ049.

     Wind Advisory from 6 PM this evening to 4 AM PST Thursday for
     ORZ049.

     Blizzard Warning until noon PST Thursday for ORZ049.

     Ice Storm Warning until 4 PM PST this afternoon for ORZ044.

WA...Winter Weather Advisory until 4 PM PST this afternoon for
WAZ029.

     Ice Storm Warning until 6 PM PST this evening for WAZ024-026-027-
     521.

     Winter Storm Warning until noon PST Thursday for WAZ030.

     Ice Storm Warning until 6 AM PST Thursday for WAZ520.

     Ice Storm Warning until 4 PM PST this afternoon for WAZ028.

&&

$$

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