Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 031151 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
340 AM PST Sat Dec 3 2016

Updated Aviation Discussion

.SHORT TERM...Today through Monday...Weak ridging and northwest flow
will continue today. Some snow showers will linger over the
mountains due to orographic effects and upslope northwest flow
aloft. A strong cold front will move through eastern WA and OR
Sunday. It will have abundant precipitation and bring substantial
snow to the mountains (mainly above 2500-3500 feet) and rain to the
valleys. Several inches of snow are possible above 2500 feet along
the east slopes of the Cascades and above 3500 feet in the
Blue/Wallowas Sunday and Sunday night. This front will also bring
falling temperatures and windy conditions. High temperatures Sunday
in the eastern part of the CWA will be steady or falling in the
afternoon. A chance of snow showers will persist Sunday night from
central to northeast OR and along the Cascades. An upper level
trough with a reinforcing shot of cold air will move through Monday
afternoon. Cold air aloft will increase instability. This will
enhance snow showers in the afternoon...especially in upslope areas
in the eastern mountains and Cascades.  Coonfield

.LONG TERM...Monday night through Friday...A secondary system is
still on track to move southeast from near Vancouver Island through
western Oregon then into California Monday night through Tuesday.
With cold air in place after the Sunday system, will see isolated to
scattered snow showers over a good portion of the area due to this
system. There do remain a few differences in the track and speed of
this system, but overall should see the snow showers. Wednesday will
be a mainly dry and cold day with a transitory upper ridge over the
region. Another system is still expected to affect the region
beginning either Wednesday night or Thursday. The ECMWF has been
consistent in bringing this system in on Thursday. Meanwhile the GFS
has preferred an earlier arrival, though it`s overall trend has been
to slow the system towards the ECMWF. Our current forecast will
continue to lean towards the faster GFS, though did lower pops over
our eastern zones for the Wednesday night period. Precip will
continue into Friday, though there are differences in how things are
handled by the mid range models. The GFS indicates a possible strong
low off the PACNW coast that would lead to warming and rising snow
levels over a good portion of the area. The ECMWF indicates a
generally cooler, onshore flow with only slight snow level rises.
Our current forecasts split the differences and will continue this
trend. 90

&&

.AVIATION...12Z TAFs...VFR conditions will mainly prevail through
the next 24 hours. Brief periods of MVFR cigs may occur at KBDN,
KRDM and KALW this morning. Will indicate some SCT MVFR clouds at
KBDN early in the period, but will keep SCT-BKN clouds above 3000 ft
AGL at KRDM and KALW for now. Some light fog may cause issues at
KYKM early this morning, but feel westerly drainage winds should
limit this fog. Overall lower cigs should run between 3500 and 9000
ft AGL. Winds at KDLS, KPSC, KALW and KPDT will run between 10 and
15 kts with higher gusts. Lighter winds of 5 to 11 kts are expected
at KRDM, KBDN and KYKM. A system will bring showers to the vicinity
of KDLS and KYKM, with light showers possible at KALW and KPDT, late
in the period. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  49  39  45  25 /  10  20  60  20
ALW  51  41  48  29 /  10  30  60  20
PSC  52  40  48  25 /   0  10  40  10
YKM  50  33  46  19 /  10  20  30  10
HRI  50  39  48  26 /   0  10  50  10
ELN  45  33  41  20 /  10  30  40  10
RDM  45  32  47  20 /  10  10  70  20
LGD  42  34  42  22 /  20  40  80  40
GCD  40  29  40  11 /  10  20  70  40
DLS  51  40  47  31 /  10  30  60  10

&&

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

$$

76/90/90



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