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fxus66 kpdt 240524 

Area forecast discussion
National Weather Service Pendleton or
924 PM PST Thu Feb 23 2017

Updated aviation discussion

Short term...tonight and Friday...a northwest flow with decreasing
showers over the region this evening which will end shortly leaving
mostly clear to partly cloudy skies overnight. Another shortwave
dropping out of western Canada will move off the Pacific northwest
coast on Friday. This will turn the flow southwesterly and will see
a few snow showers develop over the mountains in the afternoon that
will end in the evening.

Aviation...06z tafs. VFR conditions and winds less than 10 knots
will prevail for the next 24 hours. Mostly clear skies overnight
will give way to increasing high and mid level clouds on Friday.


Previous discussion... /issued 340 PM PST Thu Feb 23 2017/

Short term...tonight through Sunday night...a mid/upper level
trough will continue to persist across the Pacific northwest
through the short term period. A weak wave will exit the area to
the northeast this evening...with isolated/scattered snow showers
decreasing across the eastern mountains. Another area of low
pressure will dive south offshore the Washington/or coast Friday into
Saturday...digging across California and the Desert Southwest Saturday.
Mainly dry conditions will prevail for the lower elevations...with
slight chance to low end chance pops for the mountains. Snow levels
will generally run in the 750-1500 ft most of the precip
will remain snow. A brief period of dry conditions area wide can be
expected Saturday as shortwave ridging crosses the area as the low
digs well to the south. A more potent system will approach from the
northwest Sunday...moving inland across or Sunday night. With the initial
trajectory of the system...will keep lower elevation pops in the
slight chance to low end chance range for Sunday...with some
increase in coverage Sunday night as the trough moves inland.
With increasing upslope flow...will use mainly likely pops for the
higher elevations. With precip amounts in the one tenth inch per 6
hour range for the mountains...and snow levels remaining
low...several inches of snow will be possible across the NE or
mtns and the immediate east slopes of the Cascades. Do not expect
significant snows for the lower elevations...but some minor accums
cannot be ruled out. With the continued troughy pattern...expect
temperatures to run 5-7 degrees below normal.

Long term...Monday through Thursday. The Pacific northwest will be located
between a longwave ridge offshore and a broad upper trough east of
The Rockies Monday through Tuesday...leaving the forecast area under
a north-northwest flow aloft. Unseasonably cold temperatures...low snow levels
and scattered-numerous snow showers will result. The best chance of
snow will be over the eastern Oregon drier air from the
north will spread across eastern Washington and any snow will
primarily be orographic...especially on Tuesday. The ridge offshore
will shift eastward across Washington/or the remainder of the extended
period with drier conditions and near seasonal temperatures
returning Wednesday-Thursday. The 12z European model (ecmwf) is flatter with the
ridge compared to the GFS on Thursday which would mean more cloud
cover and cooler temperatures. No wind concerns are anticipated
during the long term period. Wister


Preliminary point temps/pops...
PDT 26 40 25 39 / 0 10 10 10
alw 27 41 26 41 / 0 10 10 10
psc 26 44 25 44 / 0 10 10 10
ykm 21 40 23 41 / 0 10 20 0
hri 27 43 25 43 / 0 10 10 10
eln 17 37 18 36 / 10 20 20 0
rdm 18 37 20 39 / 10 10 20 10
lgd 22 34 19 35 / 10 20 20 20
gcd 18 33 19 34 / 10 10 20 20
dls 26 43 25 43 / 10 20 20 10


PDT watches/warnings/advisories...

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