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Area forecast discussion 
National Weather Service Portland or
231 PM PDT Thursday Aug 21 2014

Synopsis...northwest flow will continue over the region through the
rest of this week. An upper level low pressure dropping southeast
across the inland northwest tonight could result in a some light
precipitation through Friday morning and a slim threat of
thunderstorms across the South Washington Cascades Friday afternoon.
Northwest to north flow aloft continues over the weekend maintaining
onshore low-level flow and near normal or slightly below normal
daytime temperatures. High pressure strengthens just offshore early
next week...which may result in some light offshore low-level flow.

&&

Short term...today through Saturday...upper low sitting over western
British Columbia this afternoon and will move south through Friday.
Could see some showers along the north Oregon and southwest
Washington coast this evening as the low moves into western
Washington. Still someuncertainty in drizzle forecast for overnight
and into Friday morning with NAM showing more widespread moisture so
decided to keep drizzleto marine...coastal...and southern Willamette
Valley and Cascades where moisture is highest across the models.

Later Friday...models have shifted the center of the low just a bit
south...over the Oregon Idaho boreder by 00z Saturday. Best
instability still looks like it will remain over central and eastern
Washington so thunder chances in our area should stay near the Montana
Adams area. Kept forecast consistent from this morning's update with
a slight Chace of thunder just over eastern Skamania County for the
local forecast area with showers in the north Oregon cascadse. Precipitation
chances drop off quickly Saturday as the upper low moves off to the
east. With winds out of the north and minimal afternoon sky
cover...temperatures will warm through the weekend as high pressure moves
back into the area. Bowen

Long term...upper level ridging will move onshore allowing
temperatures to increase slightly above seasonal norms for the
beginning part of next week. As the ridge begins to breakdown and
become more zonal we will see an increase in low and middle level
moisture. This will provide for an increase in cloud cover for the
latter part of next week. Do not expect any precipitation in the
near future. /64

&&

Aviation...VFR conditions this afternoon. Middle-level clouds will
increase tonight as a weak front moves over the area. The coast
may see some drizzle after 08z...but do not think there will be
much drizzle inland. Forecast confidence on ceiling height is
low...but currently think mainly MVFR ceilings for the coast and
along the lower Columbia River valley...including kttd. VFR
conditions otherwise through Friday morning.

Kpdx and approaches...VFR today with some middle and high level
clouds. Expect MVFR ceilings Friday morning around 15z...and possibly
some drizzle as remnants of a weak front moves across the area. Tj

&&

Marine...a weak front will decay as it moves across the waters
this evening. High pressure will rebuild Friday and northerly
winds will return. High pressure will hold over the NE Pacific
into next week. A thermal trough over northern California will
result in a tighter pressure gradient over the waters at times
especially in the afternoons and evenings...and S of Cascade Head.
Tj

&&

Pqr watches/warnings/advisories...
or...none.
Washington...none.
Pz...none.

&&



$$

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This discussion is for northwest Oregon and southwest Washington
from the Cascade crest to 60 nautical miles offshore. The area is
commonly referred to as the forecast area.

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