Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 240522 AAA

Area Forecast Discussion
National Weather Service Pendleton OR
1022 PM PDT Fri Mar 23 2018

.SHORT TERM...Upper low centered off the coast with a strong short
wave and jet moving into the region this evening. This short wave
will move across the forecast area overnight and keep skies
cloudy with rain and snow showers. Mountains will likely pick up
several inches of snow accumulation with the highest amounts over
the Cascades. The short wave will be moving north of the region
Saturday morning with the center of the low heading toward the
southern Oregon coast during the day. The atmosphere will remain
unstable due to cold air aloft with -35C temps at 500mb. Expect
partly to mostly cloudy skies with scattered rain and snow
showers. Highs will be in the 40s to lower 50s. Will likely have
locally breezy southwest winds again as winds aloft mix down
during the day. 94

.AVIATION...06Z TAFs...Rain and higher elevation snow showers will
come to an end from northwest to southeast across the area by early
morning. Skies begin to clear by daybreak as a weak cold front
departs the area to the east. The weakening parent low of this
system will arrive in central Oregon by mid-afternoon with another
round of light snow showers possible for the central Oregon
terminals. Predominately VFR conditions are expected through the
period aside from brief drops to MVFR/IFR visibility at RDM/BDN in
any heavier snow showers. 35-40KT west-southwesterly winds just off
the surface across the lower Columbia Basin tonight may result in
marginal WSCONDS through early morning at PDT/PSC/ALW. By late
morning these winds will begin to mix out resulting in 20-30KT gusts
that gradually taper off through the afternoon as the gradient
relaxes. Peck


.PREV DISCUSSION... /issued 500 PM PDT Fri Mar 23 2018/

SHORT TERM...Tonight through Sunday Night...The deep and cold upper
level low will continue to affect the Pacific Northwest through
tonight. A broad area of moisture within the southwest flow on the
east side of the low will continue to move across the area late this
afternoon and tonight. Thus will see good chances of precip over
much of the area. Snow levels will remain low, between 1800 and 3800
feet, this evening. The snow levels will fall areawide overnight.
Thus will see snow showers above these levels. Best chances for
measurable snow remains over the Oregon Cascade east slopes where a
winter weather advisory will be continued into Saturday morning.
Could see 3 to 8 inches in this area. Expect 1 to 4 inches across
other locations above 2000 feet. The upper low will fill and open
into a trough Saturday through Saturday night. Thus will continue to
see varying chances of snow and low elevation rain showers. Shower
coverages will decrease Saturday, and run only isolated to scattered
by Saturday night. Thus snow accumulations will be lighter and
spotty. The upper trough will then shift east through the area
Sunday with northwest flow returning by Sunday night. Snow and low
elevation rain showers will decrease further Sunday, with only a few
snow showers lingering over the mountains by Sunday night. Winds
will be locally breezy afternoons and evenings both Saturday and
Sunday. 90

LONG TERM...Monday through Friday...Models are in good agreement
indicating a mid/upper ridge of high pressure building offshore that
will put the region under the eastern flank of the ridge and thus
dominate the weather in the forecast area Monday through Friday.
Conditions will therefore be mainly dry in a north-northwesterly
flow aloft, although there could still be a few mountain rain or
snow showers due to orographic lift over the mountains, but dry at
the lower elevations. Despite northerly flow, warming temperatures
in the lower troposphere will cause a warming trend to take place
Tuesday through Friday. Maximum temperatures will be in the mid 50s
to mid 60s in the lower elevations and mostly 50s in the mountains
by Wednesday and Thursday. The nights will be just partly cloudy so
there will be substantial diurnal swings in temperatures with night
time lows in the 30s...except 20s in the mountains. Winds will be
light through that period. On Friday the pattern will change with an
upper trough developing over the region, with a northwest flow aloft
over the CWA. This will cause cooler temperatures, but moisture will
be limited. As such there will be little to no precipitation on
Friday.  Polan


PDT  32  51  29  51 /  60  20  10  10
ALW  37  52  31  53 /  70  30  10  10
PSC  37  54  29  54 /  60  20  10  10
YKM  31  52  26  54 /  60  30  10  10
HRI  34  54  29  54 /  60  10  10  10
ELN  30  47  24  49 /  60  40  10  10
RDM  24  45  22  45 /  70  20  40  20
LGD  33  45  26  43 /  60  30  10  20
GCD  31  45  27  44 /  60  20  20  20
DLS  36  52  30  54 /  70  20  20  10


OR...Winter Weather Advisory until 5 AM PDT Saturday for ORZ509.



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