Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 211201 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
400 AM PST Sun Jan 21 2018

Updated AVIATION discussion

.SHORT TERM...Today through Tuesday...A Pacific system will move
across the region today and this evening. This system will bring
precipitation to most locations as it moves through the area. The
best precip will occur mid morning through this afternoon. Snow
levels will be low this morning, generally 2000 feet or below. They
will rise to between 3000 and 3500 feet this afternoon, except over
south-central Washington where they will only rise to between 2000
and 2500 feet. Snow above these elevations will generally run
between 1 and 4 inches. The exception will be along the Cascade east
slopes where snowfall will be more persistent and more intense. Thus
could see 3 to 7 inches in these areas, and will continue the
current winter weather advisories. Winds will also be an issue with
this storm. Expect locally strong winds in the Grande Ronde valley
and will continue the current wind advisory. Winds will also be
breezy to windy along the Blue mountain foothills and over portions
of central Oregon. May see very localized strong winds in the
foothills. Meanwhile gusts of up to 40 mph will be possible over
central and north-central Oregon, and locally in the Yakima valley.
A persistent onshore flow will keep varying chances of snow and/or
rain showers going overnight tonight through Monday evening. Best
chances of showers will be near the Cascade crest and over the
interior mountains. Another Pacific system will spread snow and low
elevation rain into the region on Tuesday. 90

.LONG TERM...Tuesday night through Saturday...Models show a
progressive mid/upper level pressure pattern through the period.
A warm front moves into the region Tuesday night and Wednesday.
Snow levels rise to 4000-5000 feet during the day on Wednesday.

Then the parent mid/upper level trough pushes a cold front through
the forecast area Wednesday night with the3 front moving into .
Idaho around daybreak on Thursday. Flow aloft has a strong westerly
component on Thursday, which introduces downsloping westerly winds
east of the Cascades for precipitation shadowing and dry conditions
at lower elevations on Thursday. A ridge of high pressure builds
over the region on Friday for a short spell of dry conditions over
the Lower Columbia Basin as well as the Kittitas and Yakima Valleys
and in north central Oregon, but the northwesterly flow aloft should
keep scattered orographic snow showers over the Blue Mountains and
the Wallowa Mountains. A warm front moves into the forecast area on
Saturday with attendant overrunning precipitation for a mix of snow
and rain in the Lower Columbia Basin and snow likely in the
mountains.  Polan

&&

.AVIATION...12Z TAFs...VFR conditions will continue at all TAF sites
through most of this morning. Conditions will deteriorate during the
day and especially in the afternoon. There could be periods of MVFR
conditions as a result of a warm front bringing rain and mountains
snow to the region.   Polan

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  49  34  46  32 /  80  60  10  10
ALW  51  36  47  34 /  80  70  20  20
PSC  47  34  49  32 /  80  30  10  10
YKM  44  29  45  29 /  60  20  10  10
HRI  47  34  49  32 /  80  50  10  10
ELN  39  27  40  27 /  80  20  10  10
RDM  46  28  45  27 /  50  30  10  10
LGD  39  30  42  29 /  60  70  20  20
GCD  38  29  39  28 /  80  60  20  20
DLS  46  34  47  33 /  70  40  30  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 10 PM PST this evening for ORZ509.

     Wind Advisory from 7 AM this morning to 10 PM PST this evening
     for ORZ049.

WA...Winter Weather Advisory until 10 PM PST this evening for WAZ520.

&&

$$

90/99/99



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