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fxus66 kpdt 180526 

Area forecast discussion
National Weather Service Pendleton or
1026 PM PDT Tue Sep 17 2019

Short term...water vapor imagery showing upper low moving into
the Pacific northwest. Models continue to indicate a more steady
rain across central and northeast Oregon this evening and overnight.
Radar and satellite would confirm this trend. Remainder of the
forecast area looks to be more showers associated with the cold
unstable low. The upper low will be directly over the region on
Wednesday. Expect showers with isolated thunderstorms. Models have
been consistent for several days now with fairly high thunderstorm
pops. Temps of -4c at 700mb and -20c at 500mb would support some
small hail with the heavier showers. Precipitation should continue
into Wed night although decreasing in coverage and intensity a
few hours after sunset. The low is moving into Idaho on Thursday
and showers and storms will be more confined to the northeast
Oregon mountains at this point.

Aviation...06z tafs. Showers will continue over the taf sites
tonight into Wednesday. At times the showers could be moderate.
The upper low will be over the region Wed with a fair amount of
instability. Isolated thunderstorms are possible. Ceilings mostly
030-070. Winds 5-15kt.

Previous discussion... /issued 536 PM PDT Tue Sep 17 2019/

Short term...this afternoon through Friday...forecast still
looks on track with a rainy couple of days expected. Steadier rain
with good feed of Pacific moisture pushing inland along and ahead
of cold front with abundant upper-level support with jet aloft.
Transition to more convective type showers tonight as the upper
low pushes overhead. Instability is modest tomorrow, but with cold
temps aloft (h5 - 20 and lower) expect some isolated
thunderstorms with small hail possible. Rainfall amounts through
Wednesday night will range from 0.2-0.6 inch with higher amounts
along the Cascades and Central/Northeast or mtns. Low slowly
shifts east on Thursday with lingering showers and isolated storms
for central/eastern or and far southeast Washington. Snow levels tonight
through Thursday will fluctuate between 6500-8000ft. For Friday, a
weak disturbance riding down the east side of approaching ridge
and behind the departing low could kick off a few mountain
showers, but generally dry conditions expected. Cooler than normal
conditions continue with highs today and tomorrow in the 50s to
around 70, warming a few degrees Thu and again Fri. Strong winds
aloft ahead of the approaching low could lead to localized breezy
winds in some areas with high gusts along exposed ridges through
tonight, otherwise generally light winds expected.

Long term...brief ridging will move into the region for Saturday
with drier weather and warmer temperatures expected. Unfortunately
our break from the active weather looks to be short lived as yet
another upper level low moves into the Pacific northwest by
Sunday. Showery conditions can be expected across much of the area
through Monday morning with highest chances in the mountains. The
system will not have much in the way of instability to work with
so not expecting any thunderstorm activity as the trough moves
through. Models diverge toward the beginning of next week with the
overall evolution of the upper level flow pattern. The European
model has more of a progressive system giving a quick shot of
precipitation before dry northwest flow returns. The GFS cuts off
this energy just south of the area leading to a few days Worth of
unsettled weather. Due to uncertainty, have kept slight pops
mainly over the higher terrain to start next week. Richards


Preliminary point temps/pops...
PDT 51 65 48 67 / 50 60 40 40
alw 54 67 51 70 / 50 50 40 40
psc 53 70 52 73 / 40 30 40 10
ykm 46 67 46 71 / 40 40 30 10
hri 52 70 51 73 / 50 30 40 20
eln 45 64 44 69 / 60 50 30 0
rdm 42 59 40 65 / 70 80 60 10
lgd 47 59 44 61 / 90 90 70 60
gcd 44 58 43 61 / 90 80 60 60
dls 51 66 50 67 / 70 70 30 10


PDT watches/warnings/advisories...

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