Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pendleton or
735 PM PST Thursday Dec 12 2013
Update...a mixture of very light freezing rain and snow has begun
to fall at kpdt and a few other stations during the past hour as a
band of precipitation moves across the area. This area is moving
quite fast and do not expect the precipitation with this band to
last too long. Dew point temperatures across the area are well below
freezing and this may causing enough cooling effect to turn all
precipitation over to snow before it ends. Am expecting very little
accumulation from this. There will be on and off light mixed
precipitation though the night as a weather disturbance moves across
the region. Winds in the Grande Ronde Valley have been diminishing
and will likely be able to let the High Wind Warning expire there
for the southern Grande Ronde Valley at 10 PM. Temperatures on
Friday will rebound into the middle 30s to middle 40s across the forecast
area...even in the mountains. This will quickly melt any freezing or
frozen precipitation that falls tonight. Will keep the Winter
Weather Advisory going although it looks like the precipitation will
end before the advisory expires...maybe even before the evening is
over. High pressure aloft will build over the region by late Friday
and continue through Saturday. There will be another weak
disturbance Saturday night and early Sunday but do not expect much
if any precipitation from this. The flow will then become northwest
on Sunday and Monday with near seasonal temperatures into early next
Aviation...06z tafs...conditions may drop to MVFR at times in mixed
precipitation due to lowered ceilings and visibilities but most of the
time it will be VFR tonight. VFR conditions are then expected on
Saturday and Saturday evening at all taf sites. Winds will remain
light from the southwest at 5 to 10 kts overnight and on Friday. 88
Previous disc... /issued 156 PM PST Thursday Dec 12 2013/
Short term...tonight through Saturday...winter mix of precipitation
is expected tonight over most of the lower basins. Although most of
the precipitation will be light there certainly could be travel
problems due to freezing rain and sleet. Numerous advisories will be
issued prior to 3 PM for tonight. Temperatures are expected to rise
above freezing by afternoon Friday allowing for a meltoff of any
ice. The winds in the lower part of the Grande Ronde Valley are
still up today and will continue to be strong through this evening
before subsiding overnight. The High Wind Warning for this area will
continue through late this evening. A general drying trend is
expected Friday afternoon and Saturday but low level moisture and
clouds may remain...with indications that lower elevation fog and
stratus may form Friday night into Saturday. High temperatures on
Saturday will be mostly in the 40s. 78
Long term...Saturday night through Monday night. Northwest flow is
expected through much of the period with some showers along the
Washington Cascades. Soundings indicated some patchy fog possible
Saturday night and early Sunday for the lower elevations.
Temperatures will be warming with daytime highs slightly above
seasonal levels. 93
Tuesday through Thursday night...progressive west/northwest flow
will continue Tuesday. Expect light precipitation chances over the
Cascade mountains in the morning and early afternoon...with a slight
chance of snow hitting the Blue Mountains by the evening. Another
weather system looks to clip the area on Wednesday. This will bring
a chance of rain and snow showers to all areas. Lower elevations
should start off as rain...but snow levels look to drop down to the
basin floor by Wednesday evening. Right now snow accumulations
across the lower elevations look to be in the 0.5"-1.5" range. No
significant mountain accumulations stand out at this time. As the
system exits the area...drier northwest flow will return Thursday. 89
Preliminary point temps/pops...
PDT 28 40 28 42 / 70 20 10 10
alw 29 39 30 42 / 70 30 10 10
psc 27 37 28 40 / 70 10 10 10
ykm 24 36 27 38 / 30 10 10 10
hri 27 39 28 41 / 70 10 10 0
eln 23 39 24 41 / 30 20 10 10
rdm 26 42 21 43 / 30 10 10 0
lgd 25 37 25 38 / 50 40 10 10
gcd 22 37 18 40 / 40 30 10 0
dls 30 40 30 42 / 60 20 10 10
or...Winter Weather Advisory until 7 am PST Friday orz507.
Winter Weather Advisory until 4 am PST Friday orz044-508.
Winter Weather Advisory until 4 am PST Friday orz041.
High Wind Warning until 10 PM PST this evening for Ladd and
pyles canyons in the orz049.
Washington...Winter Weather Advisory until 7 am PST Friday waz029.
Winter Weather Advisory until 4 am PST Friday waz028.
Winter Weather Advisory until 4 am PST Friday waz024.
Friday : yellow
Saturday : green
Sunday : green
Green: none or limited need for watches, warnings, or advisories.
Yellow: a few watches, warnings, or advisories possible or in effect.
Red: numerous watches, warnings, or advisories possible or in effect.
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