Flood in Washington, December 30 to 31, 2017

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
400 AM PST Sat Dec 30 2017

Updated AVIATION discussion

.SHORT TERM...Today through Monday...A cold front which moved across
most of the forecast area last evening is now moving across far
northeast Oregon and southeast Washington. The front just passed
KMEH not too long ago. Winds behind the front have become gusty from
the west to northwest in most areas with a few stations reporting
southwest to northwest winds of 15 to 30 mph. Ahead of the front
winds are from the southeast to southwest. A band of showers is
currently moving across Union and Wallowa Counties in Oregon ahead
of the front. The air behind the front is cooler in the higher
elevations, however, colder air from previous inversions remain
trapped in the Lower Columbia Basin and adjacent low lands to the
north and west where temperatures are still in the upper 20s to
lower 30s with light winds. The cold front was not strong enough to
scour out these areas. Drier air will move into the region today and
tonight and continue through the short term with a cooling trend in
the higher elevations through Monday. It will be dry with no
precipitation expected...except perhaps a few light snow showers
over the eastern and northeast mountains due to upslope winds. In
the Lower Columbia Basin and adjacent lower elevations there is a
chance that fog may re-develop with surface based inversions
persisting. However with the drier air moving in, it may take a
couple of days for this to happen. Winds in the higher elevations
will gradually decrease tonight into Sunday and then remain light. 88

.LONG TERM...Monday Night through Friday...Models show a ridge of
high pressure over the region through Tuesday night for dry
conditions through Tuesday night. Moisture works its way north into
central and NE Oregon on Wednesday in a southwest flow aloft. This
introduces a slight chance of rain and snow on Thursday, but the
Lower Columbia Basin looks to be dry through Wednesday. Thursday and
Friday a disturbance moves from northern California into Oregon for
a chance of a rain and snow mix in central and north central Oregon
as well as along the Foothills of the Blue Mountains and a slight
chance of snow in the Blue Mountains and in central and south
central Washington.  Polan

&&

.AVIATION...A cold front moved through the forecast area Friday
evening and brought drier and colder air into the region, which
changed the vertical temperature profile sufficiently to destroy the
inversion and thus scour out the low clouds and mist. This will
allow VFR conditions to occur through this afternoon. Around sunset
radiational cooling near the ground will produce IFR/LIFR at KPSC,
KYKM and KPDT.  Polan

 evening before midnight local VFR conditions persist at taf sites
kykm and kdls and kalw and kpsc. However conditions at these
locations should slowly improve as a cold front passes through the
entire region aft 10z. Then a return to mostly vfr conditions can be
expected for all taf sites. Meanwhile brief wind gusts to 30 kts are
possible tonight and tomorrow.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  42  25  33  21 /  10   0   0   0
ALW  43  28  36  24 /  10  10   0   0
PSC  42  27  36  24 /   0  10   0   0
YKM  41  24  35  22 /  10   0   0   0
HRI  43  26  35  24 /   0   0   0   0
ELN  38  21  32  19 /  20   0   0   0
RDM  40  18  39  17 /   0   0   0   0
LGD  35  20  34  20 /  10  10   0   0
GCD  36  18  37  21 /  10   0   0   0
DLS  47  30  39  28 /  10   0   0   0

&&

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

&&

88/99/99