Area Forecast Discussion


780 
FXUS66 KPDT 152325 AAA
AFDPDT
Area Forecast Discussion
National Weather Service Pendleton OR
325 PM PST Fri Dec 15 2017
.SHORT TERM...Tonight and Saturday...The latest Pacific cold front 
continues to move across the area late this afternoon. The front and 
main precip band currently runs from near Spokane south-southwest to 
the Blue mountain foothills, then to central Oregon. A mix of 
freezing rain, snow and sleet has been accompanying this front. The 
precip has largely ended over the Lower Columbia Basin zones, and 
have cancelled the winter weather advisory for those zones. Will 
continue the winter weather advisory for the eastern Blue mountain 
foothills zones until 7 PM, though these advisories may be eligible 
for lowering prior to that time. Snow levels have been rising 
slightly behind the front, but cold air advection should increase 
this evening to lower the snow levels to near the Basin floor 
overnight. This cold air advection, plus increasing winds and 
mixing, should eliminate the remaining weakened inversions over the 
area. Flow into the interior mountains will keep some showers going 
through the night into Saturday morning over these mountains and 
along adjacent foothills. Also should see showers continue along and 
near the Cascade crest tonight and Saturday. 90 
Saturday night through Sunday...A series of weak waves will move 
through an offshore upper level ridge Saturday night and Sunday. 
This will weaken the ridge with time. These waves will keep mostly 
cloudy skies with rain and snow along the Cascades Saturday night 
and Sunday. Light snow may develop in the northeast OR mountains 
Sunday. Coonfield 
.LONG TERM...Sunday night through Wednesday night...A broad dirty 
upper level ridge will slowly move across WA and OR Sunday night 
through Tuesday. The series of weak waves will continue to flow over 
the ridge with varying amounts of rain and mountain snow. Rain 
shadowing will limit precipitation to light rain at most in the 
Lower Columbia Basin, Yakima Valley, and Kittitas Valley. A rain 
snow mix is possible in North Central OR and Central OR during this 
time. Tuesday night an upper trough will move from the Gulf Of 
Alaska to the WA and OR coast. This will bring cooler air with a 
better chance of rain and mountain snow Tuesday night through 
Wednesday night.  Coonfield
Thursday through Friday...ECMWF/GFS/Canadian models coming into 
better agreement with mid/upper level ridging building across the 
eastern Pacific, and a trough digging across the Four 
Corners/Rockies region. Dry conditions can be expected area wide 
with generally light winds as surface high pressure will reside 
nearly overhead. There are still some model differences, but the 
trend is to produce more of a northerly flow, versus a NE flow 
regime previously depicted. A cooldown is still expected, but the 
most frigid air will remain east of the area. Expect high 
temperatures in the 30s for the lower elevations, with upper teens 
to mid 20s for lows. 80 
&&
.AVIATION...0Z TAFs...MVFR and IFR conditions will be possible at 
all TAF sites as a front moves out of the area this evening. There 
will be some rain or snow at KPDT and KALW early this evening. This 
system will help to mix out the low clouds and fog...but stratus 
expected to redevelop tonight. Drier air will move into the area 
tomorrow. Winds will be light except at KDLS. 76 
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT  29  39  31  42 /  50  20   0  10 
ALW  31  41  33  43 /  60  20   0  20 
PSC  30  42  33  41 /  10  10   0  10 
YKM  27  41  28  39 /   0   0  10  20 
HRI  29  41  32  42 /  10  10   0  10 
ELN  28  39  29  37 /  10  10  10  30 
RDM  22  38  24  44 /  20  10  10  10 
LGD  29  35  25  38 /  60  20   0  20 
GCD  28  37  25  39 /  50  20   0  20 
DLS  36  45  36  43 /  10  10  20  20 
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 7 PM PST this evening for ORZ507.
WA...Winter Weather Advisory until 7 PM PST this evening for WAZ029.
&&
$$
90/76/80/76