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Area forecast discussion 
National Weather Service Pendleton or
230 PM PDT Friday Mar 27 2015

Short term...tonight through Monday. Upper level trough and cold
front approaching the coast. Models have been indicating instability
over central and northeast Oregon this afternoon into the evening.
Satellite show cumulus is starting to develop. Will continue with a
slight chance of thunderstorms over this area. Otherwise the passage
of the frontal boundary will bring cloudy skies late evening and
overnight with showers. Westerly flow aloft Saturday with clearing
skies. Combination of cold advection and pressure rises will result
in breezy to windy conditions overnight and Saturday. Expecting some
light rain over the Columbia Basin so will hold off on any blowing
dust for now. Temperatures about 5-15 degrees cooler tomorrow. Westerly
flow aloft continues Sunday with a system passing by to the north.
Expect some middle and high level clouds. Winds much lighter. An
approaching trough will turn the flow more southwest on Monday.
Skies will remain partly cloudy with highs in the 60s to lower 70s.

Long term...Monday night through Friday. A return to more
Spring-like temperatures and showery conditions can be expected next
week. A strong cold front on Tuesday will lower snow levels to near
4000-5000 feet...and cold air behind the front will bring snow
levels down to 3500 feet Tuesday night and Wednesday. There is not
a significant amount of moisture with the front but there will
likely be several inches of snow accumulations in the mountains.
Deep cold air aloft on Tuesday (500mb temperatures down to -32f) will
steepen lapse rates...and there could be graupel mixed with rain
showers in the lower elevations. Sustained winds at 20-30 miles per hour are
forecast for most of the forecast area Tuesday. Another shortwave
will quickly follow on Wednesday. There are differences in the
timing and position of this next the European model (ecmwf) is faster and
farther south than the GFS and Canadian...but the overall synoptic
pattern Wednesday and Wednesday night is a northwest flow aloft that
will bring a chance of snow showers in the mountains and a slight
chance rain showers (snow above 3500 feet) elsewhere. There should
be a break in precipitation Thursday. On Friday...there are
significant differences in the GFS and European model (ecmwf) as both models become
out of phase with each other. If the GFS verifies...there will be
another trough bringing showers and breezy winds to the region on
Friday while the European model (ecmwf) keeps the upper level ridge over WA/OR. Used
the ecens for the forecast which is a compromise of both solutions
and introduced 20-40 percent chance of showers in the mountains but
dry conditions elsewhere. Wister


Aviation...00z tafs. Latest visible satellite shows cumulus clouds
developing from SW Deschutes County northeast to the northern Blue
Mountains. This is the area that has the best potential for
isolated late afternoon and evening thunderstorms.
Therefore...there will be towering cumulus or cumulonimbus clouds in the
vicinity of kbdn, krdm, and kpdt and possibly kalw for the next 6-8
hours. The timing of the cold front will be near the Cascade Range
around 10 PM this evening then over the Columbia Basin around
midnight and near the Idaho border by 4am Saturday. West winds just
ahead and behind the front will increase to 15-25 knots gusting to
35 knots. Rain showers may also lower ceilings/visibilities to MVFR
tonight...mainly near kpdt and kalw. Winds and clouds will decrease
from 18z-00z Saturday. Wister


Preliminary point temps/pops...
PDT 49 64 40 65 / 40 10 0 0
alw 51 66 43 65 / 40 10 0 0
psc 50 67 42 68 / 30 10 0 0
ykm 44 66 37 65 / 20 10 10 10
hri 49 67 41 68 / 30 10 0 0
eln 44 62 37 64 / 20 10 10 10
rdm 38 61 31 65 / 30 10 0 0
lgd 43 60 34 61 / 40 20 0 0
gcd 41 60 33 63 / 30 20 0 0
dls 49 66 39 67 / 30 20 10 10


PDT watches/warnings/advisories...

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