Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 221100
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
300 AM PST Sun Jan 22 2017

.SHORT TERM...Today through Tuesday...An upper level trough
continues to be positioned off the coast placing the forecast area
under a southwest flow aloft. A shortwave rotating through the trough
will move across the forecast area today bringing another round of
precipitation. The leading edge of light precipitation is already
moving into central Oregon at this time and regional radars show more
precipitation behind it. This precipitation will spread northeast
across the forecast area through the morning then exit this
evening. Snow levels will vary from around 1500 feet along the east
slopes of the Cascades to around 2500 to 3000 feet over the easter
portion of the forecast area. This will result in a mix of rain and
snow in the lower elevations and snow in the mountains. Some light
snow accumulations of 1 to 2 inches will be possible around the
Yakima and Ellensburg areas today otherwise expect snow
accumulations to be confined to the mountains. The upper level
trough begins to move inland on Monday but the heart and energy of
the trough drops south which will limit us to just some showers
over central Oregon. By Tuesday the trough is pushing off to the
east with a ridge of high pressure building just off shore. This
will allow the development of a cold northerly flow aloft to advect
in a cooler airmass with some upslope showers possible over the
eastern oregon mountains.

.LONG TERM...Tuesday night through Saturday night...Tuesday night
through Friday night a large amplitude mid/upper level ridge of high
pressure builds just offshore thus putting the interior Pacific
Northwest on the eastern flank of the ridge for a northerly flow
aloft, in which a weak upper level disturbance moves southward
through the forecast area Tuesday night through Thursday afternoon
for a slight chance of snow in central Oregon and the Blue
Mountains. Otherwise, the northerly flow will produce dry conditions
Tuesday night through Saturday night. As the ridge builds slowly
over the region a surface-based inversion due to sinking air
aloft associated with the ridge will trap moisture in the boundary
layer thus producing patchy freezing fog and low stratus clouds
across the Lower Columbia Basin and adjacent valleys as well as
along the Foothills of the Blue Mountains of WA/OR.  Polan


&&

.AVIATION...12Z TAFs...IFR conditions will occur in KBDN, KRDM,
KDLS, and KYKM as a disturbance moves north and brings mixed rain
and snow. The lower cigs/vsby will last around 6-9 hours and will
start around 10Z at KRDM/KBDN, 12Z at KDLS, and 15Z at KYKM.
Generally MVFR/VFR will prevail at other TAF sites.  Polan


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  42  28  35  23 /  70  10  10  10
ALW  44  30  36  26 /  70  20   0  10
PSC  38  26  34  22 /  70  10   0   0
YKM  38  23  34  17 /  80  10   0   0
HRI  37  27  35  23 /  60  10   0   0
ELN  35  22  33  17 /  80  10   0   0
RDM  38  22  33  15 /  70  30  20  10
LGD  38  23  33  19 /  80  20  10  10
GCD  39  24  33  18 /  70  20  20  10
DLS  38  30  36  25 /  80  10  10   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

91/99/99



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