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Area forecast discussion 
National Weather Service Pendleton or
255 am PDT Wednesday Sep 17 2014

Short through Friday night...middle and high clouds are
spreading over eastern Washington and Oregon in southerly flow aloft
ahead of a trough located offshore. Water vapor satellite shows a
wave moving through southeast Washington at this time. However low
levels are still very dry so very little...if any...precipitation is
reaching the ground. More weak waves will move through this
afternoon and tonight but the main effect will be to increase middle
level moisture so that a stronger wave on Thursday will trigger some
showers and thunderstorms across eastern Oregon Thursday. A few
showers are possible near the Cascades today. There is some
instability over the Cascades that may trigger a few thunderstorms
along the Oregon Cascades this afternoon. Stronger southerly winds
aloft may mix to the ground at times today in central Oregon. Winds
and low relative humidity may cause fire weather concerns in the southern half of
fwz 640 this afternoon. The trough will move across Washington and
Oregon Thursday...but it will be splitting apart as it moves
through. There will be enough instability with the trough that a few
thunderstorms will develop from central to northeast Oregon Thursday
afternoon and evening. Friday the upper level ridge will rebuild
over Washington and Oregon. This will dry out eastern Washington and
Oregon with a sunny warm day...but a cool night Friday as strong
radiational cooling will occur under clear skies and light winds.

Long term...Saturday through Tuesday...a middle/upper level high
pressure ridge persists over the Pacific northwest from the weekend
through Monday for dry conditions and daytime high temperatures 5-10
degrees above normal. The wind flow aloft backs to the southwest
Monday night and Tuesday as a result of the ridge axis moving east
of the forecast area, thus allowing for increasing middle and high
clouds spreading over the region Monday night and Tuesday. The
clouds will moderate the daytime high temperatures on Tuesday. Polan


Aviation...12z tafs...VFR conditions are expected for the next 24
hours. There will be middle and high clouds between mainly 150-250 feet
tonight and Wednesday. At this time it looks like any thunderstorms
will stay to the west of krdm and kbdn on Wednesday afternoon. Winds
will remain generally light and 15 kts or less through the period.


Preliminary point temps/pops...
PDT 86 58 82 54 / 10 10 20 20
alw 88 63 83 60 / 10 10 20 20
psc 88 60 85 58 / 10 10 20 10
ykm 90 58 82 54 / 10 10 20 10
hri 87 55 84 55 / 10 10 20 10
eln 92 60 81 54 / 10 20 20 20
rdm 86 52 76 44 / 10 20 20 20
lgd 88 52 81 50 / 10 10 20 20
gcd 91 52 80 48 / 10 10 30 20
dls 89 60 81 57 / 10 20 20 20


PDT watches/warnings/advisories...

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