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Area forecast discussion...update 
National Weather Service Pendleton or
355 PM PST sun Nov 23 2014

Updated for aviation discussion

Short term...a disturbance will pass through our area this evening
producing some rain showers specifically over and near the
blue/Wallowa Mountains...along with the John Day Highlands...and
over the Washington/or Cascades. Snow levels will dip toward 3500 feet
tonight and locations such as meh and Tollgate could experience some
snow accumulation. Otherwise the disturbance is forecast to race southeast
overnight with drier conditions expected early Monday. A weak ridge
of high pressure will build into the area Monday morning before
another storm system effects the two state area Monday night. Clouds
and showers are expected into Tuesday along with above normal
temperatures and rising snow levels. In additional the winds across
the area will become breezy to windy this evening and then again on
Tuesday with the passing storm system.

Long term...Tuesday night through Sunday night...a very busy
extended as active weather threatens the Holiday weekend. A ridge
of high pressure will continue to build over the area by middle week.
Moisture is expected to overrun just to the north of the
County Warning Area...mainly affecting the Spokane County warning area. Slight chance to chance
precipitation will remain over the east slopes of the Washington
Cascades and the mountains of northeast Oregon through Wednesday
night. A strong cold front moving south from Canada will flatten
out the ridge of high pressure Thursday...providing a moist westerly
flow to the area for Thanksgiving. Right now have not gone too
aggressive with probability of precipitation on it is expected to be all
rain...and there may be a decent rainshadow affect for the basin.
So 20-30 percent probability of precipitation in the forecast for the lower elevations with
30-50 percent for the mountains.

Warm southerly flow from the south looks to slow the arrival of the
Canadian cold front until late Friday night into Saturday. Saturday
Onward is where it gets interesting. These two air masses continue
to battle through the Holiday weekend...and there is still some
model discrepancy as to how much precipitation will fall across the
area...and the time it will fall. The current overall consensus
indicates that the cold air will reach about 50 miles south of the
I-84 corridor...and all areas to the north will see snow as the
general form of precipitation. Central Oregon and the John Day
Highlands is where it gets challenging. These areas could see a
rain snow mix...or possibly freezing rain. Have not introduced the
freezing rain to the forecast due to timing and uncertainty. By
Sunday morning parts of north central Oregon and southern Washington
are expected to be below freezing and may have some snow
accumulations. Will continue to monitor the forecast and make
updated as changes occur. Weber


Aviation...00z tafs...showers continue to move across most taf
sites this evening. Peak activity should be through 06z...with some
lingering showers at kalw and kpdt through 09z. Krdm...kbdn...and
kykm may escape the showers due to rainshadowing. Winds will be a
bit breezy as well with wind speeds 10-15kts... gusting to 25kts at
times. Ceilings tonight are in the potential for mist/fog
increases. Have introduced lowered ceilings/visible into the MVFR/IFR
category at taf sites of concern. Ceilings should start to improve after
18z and become scattered-broken 7-10kft. Weber


Preliminary point temps/pops...
PDT 35 48 40 58 / 20 10 40 30
alw 35 48 42 60 / 20 10 40 40
psc 34 48 40 58 / 10 10 40 30
ykm 30 42 33 53 / 10 10 30 30
hri 34 49 40 58 / 10 10 40 30
eln 27 42 33 52 / 10 10 40 30
rdm 27 47 34 61 / 10 10 30 20
lgd 32 45 34 53 / 40 10 50 60
gcd 25 41 31 55 / 30 10 40 30
dls 35 51 40 54 / 30 10 40 40


PDT watches/warnings/advisories...

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