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fxus66 kpdt 082250 

Area forecast discussion
National Weather Service Pendleton or
144 PM PST sun Dec 8 2019

Updated aviation discussion.

Short term...tonight through Wednesday...upper trough is exiting
the region this afternoon and an upper level ridge is building in
behind it. The ridge will be the main weather feature through the
day on Tuesday. This will result in a continuation of stratus and
fog in the lower valleys. Have issued a dense fog advisory for
the Columbia Basin and adjacent foothills and valleys for tonight
and early Monday. The fog may become even more widespread Monday
night and Tuesday with the ridge overhead. Away from the fog
conditions will be fair with mild temperatures and just a few
clouds. By Tuesday evening a weak frontal band will cross the
Cascades for a chance of showers and mountain snow showers.
However quantitative precipitation forecast amounts will be rather light Tuesday night. By late
Wednesday the next much stronger system may reach the Cascade east
slopes near the very end of the day for a chance of rain and
mountain snow. The fog could linger in the Columbia Basin into
Wednesday. 78

Long term...Wednesday night through Sunday...models in good
agreement on an active pattern beginning Wednesday and continuing
into the first half of next weekend. A wet storm system looks to
impact the region Wednesday night through Friday, bringing
widespread rain and mountain snow to the forecast area. Behind
this system, a persistent moist, westerly flow will lead to
continued chances for scattered precipitation through at least
Saturday afternoon. Initially, snow levels for thursday's system
will range between 4000-6000 feet, gradually lowering to 500-1000
feet by Sunday morning. Ensembles showing the potential for quantitative precipitation forecast
ranging between 0.50-1.50" through the weekend for the higher
elevations, and ~0.30" possible on average for the Columbia Basin.
As snow levels lower, may need to consider winter weather
highlights, especially for the Cascades as well as higher terrain
of central and northeast Oregon. A weak upper level ridge begins
to move onshore by next Sunday, bringing a brief break from the
active weather. With a Pacific flow, temperatures expected to
remain near normal through next weekend with highs in the 40s and
lows in the 20s/30s. Richards


Aviation...00z tafs...fog has thinned out a bit but still remains
dense with visibility of 1/4 mile for kykm/kpdt. Patchy fog also
impacting kalw and kpsc. Expect dense fog to once again develop and
impact all taf sites except kbdn/krdm. LIFR/IFR conditions expected
for kpdt/kalw/kpsc/kykm/kdls with VFR conditions for kbdn/krdm. Fog
will remain dense across the Columbia Basin through the day Monday.


PDT watches/warnings/advisories...
or...dense fog advisory from 7 PM this evening to noon PST Monday for

Washington...dense fog advisory from 7 PM this evening to noon PST Monday for


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