Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 192321 AAA

Area Forecast Discussion...updated
National Weather Service Pendleton OR
320 PM PST Thu Jan 19 2017

Updated Aviation Discussion

.SHORT TERM...Tonight Through Saturday night...Other than some
scattered rain and mtn snow showers this evening expect mainly dry
conditions. There could be some patchy fog or freezing fog
redeveloping/continuing in the Yakima and Kittitas Valleys through
the overnight. The next system, an occluded front, moves into the
area early Friday morning in Central OR...spreading north into the
Columbia Gorge Region during the mid to late morning hours. Even at
this close time range there remains some timing difference between
the models...the GFS is about 3-6 hrs faster than the latest NAM.
For now took a blend of this guidance for timing purposes...which
also matches up fairly well with the latest RAP. Latest low/mid
level thicknesses and model soundings support rather low snow levels
Friday morning, and only rising slightly Friday afternoon(1000 feet
or less Columbia Basin....2500-3000 feet Central OR and NE Mtns).
The low level winds are forecast to be easterly into N. central OR,
the Columbia Gorge, Simcoe Highlands, East Slopes of the Cascades,
and the Yakima/Kittitas valleys. This will mean an upslope component
to the flow here. This should hold temps/thicknesses down and
increase precip totals in these zones Friday into Friday night. For
this reason, and in collaboration with neighboring offices decided
to go ahead with a low end winter weather advy for the Col Gorge, N.
Central OR and the Simcoe Highlands for a general 1 to 4 inches of
snow and perhaps some localized light freezing rain. Will need to
monitor the Yakima Valley, Kittitas Valley and the East Slopes of
the WA cascades for the possible need of an advisory as well. For
now, held snow totals just below advy criteria in these zones (1-2
inches Yakima/Ellensburg) 2-4 inches East Slopes of the WA Cascades.
High temperatures will be in the 30s areawide for Friday afternoon.
The area will see a brief break in the activity late Friday night
and early Saturday, before another weaker front moves in Saturday
afternoon. This will bring renewed chances for a rain/snow mix to
the area, with snow levels between 1500-3000 feet across the
forecast area. High temperatures will again be in the 30s to lower
40s Saturday afternoon. Overnight lows throughout the short term
period will mainly be in the mid 20s to lower 30s....except some
upper teens and lower 20s mtns. This should allow for gradual
snowmelt to continue in most locations and will hopefully preclude
any significant flooding issues. Late Saturday night another,
stronger front begins to push into the area...bringing chances of
snow to Central OR prior to daybreak Sunday. 77

.LONG TERM...Sunday through Thursday...An active weather pattern
will continue through Monday. A strong disturbance will rotate
around an offshore low into eastern WA and OR Sunday with a mix of
rain and snow. A weaker disturbance will rotate into the area Monday
as the low moves southeast along the coast. Snow levels will range
between 500 and 2500 feet. Dry northerly flow will begin Monday
night with decreasing pops. A few showers may linger over the
mountains Tuesday. An upper level ridge will develop offshore that
will keep WA and OR dry Wednesday and Thursday. Patchy freezing fog
may develop near the rivers early Tuesday and increase in coverage
Wednesday and Thursday as surface inversions get stronger due to
radiational cooling at night. Coonfield


.AVIATION...0Z Tafs..IFR cigs and vsby in fog will continue at
KYKM. At KDLS MVFR/IFR visibility with lowering clouds overnight and
-SN developing after 8Z. Elsewhere, mainly VFR conditions should
prevail with sct-bkn clouds above 5000 feet agl tonight. Increasing
clouds overnight. Winds will generally be 10kts except KRDM and
KBDN. 76


PDT  31  38  29  39 /  10  50  50  30
ALW  33  40  31  41 /  10  30  50  20
PSC  26  38  28  36 /  10  60  60  20
YKM  27  35  26  36 /  10  70  70  40
HRI  27  36  28  36 /  10  60  60  20
ELN  26  34  25  35 /  20  70  70  40
RDM  27  37  23  39 /  20  70  60  50
LGD  31  36  27  34 /  10  40  40  30
GCD  28  37  24  37 /  10  60  60  50
DLS  30  34  29  37 /  10  70  70  60


OR...Winter Weather Advisory from 7 AM Friday to 4 AM PST Saturday
     for ORZ041-510.

WA...Winter Weather Advisory from 7 AM Friday to 4 AM PST Saturday
     for WAZ024-521.



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