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Area forecast discussion 
National Weather Service Pendleton or
258 am PDT Monday Aug 31 2015

Short term...Monday through Wednesday...models are in good
agreement in having a broad upper level trough over the Pacific
northwest and western Canada. A westerly flow will be crossing the
area through Tuesday morning and precipitation will be limited to
some light showers along the Washington Cascades, perhaps making it
down to Ellensburg at times. By Tuesday afternoon an upper low will
be dropping south along the British Columbia coast and deepening the
trough southward. This will turn the flow more southwesterly and
bring the light showers into the Oregon Cascades as well on Tuesday
afternoon. Tuesday night the low will send a wave ashore and a
slight chance of showers will expand into the eastern mountains and
Wallowa County overnight while the rest of the area aside from in
and near the Cascades will remain dry. On Wednesday the wave will
bring a chance of rain showers to the mountains and a slight chance
to the lower elevations though the Columbia Basin will remain dry.
Rain amounts will generally be less than a tenth of an inch.
Temperatures will be in the 70s and lower 80s today and Tuesday but
with the trough moving ashore, temperatures will be in the middle 60s
to middle 70s on Wednesday. Perry

Long term...Wednesday night through upper level trough
will be exiting the area Wednesday evening with lingering chances
for showers mainly over the eastern mountains. Thursday will be in
between storms systems so mostly dry conditions are expected with
cool temperatures. On Friday an upper level trough will be over the
area with a good chance for showers and thunderstorms especially
during the afternoon and evening. After Friday the medium range
models diverge. The European model (ecmwf) closes a low off over the region while the
GFS is much more progressive. If the European model (ecmwf) is correct there could be
significant rains on Saturday and Saturday night especially over
eastern Oregon. The GFS solution would be dry. For now have kept low
chances for showers and thunderstorms over the eastern mountains for
Saturday and Saturday night until it becomes a bit more clear on
what will transpire on the weekend. By Monday it should be drying
out with westerly flow. Temperatures will be cool for much of the
period with some freezing temperatures at night possible in the
mountains and snow levels 6-7 thousand feet. It will warm up a bit
toward the end of the weekend into early next week with temperatures
closer to normal for this time of year. 78


Aviation...12z tafs...VFR conditions will prevail through the
forecast period. There will be extensive high clouds at around 20000
feet above ground level. There could be a few stratocumulus at 6-8k feet but not
expecting these clouds to produce a ceiling. Winds will be mainly
westerly at 7-12 knots after 18z becoming light terrain driven after
06z. 78


Preliminary point temps/pops...
PDT 77 53 78 55 / 10 0 10 20
alw 78 59 80 60 / 10 0 10 20
psc 80 55 82 57 / 10 0 10 10
ykm 73 51 75 51 / 10 10 10 20
hri 79 56 80 56 / 10 0 10 10
eln 73 52 76 50 / 20 20 20 20
rdm 77 43 78 46 / 10 0 0 20
lgd 77 46 81 48 / 10 0 0 10
gcd 81 46 85 48 / 10 0 0 10
dls 79 61 79 60 / 10 10 10 20


PDT watches/warnings/advisories...

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