Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Portland or
222 PM PST sun Feb 7 2016
Synopsis...an upper ridge will continue over the Pacific northwest
through Tuesday. Resultant offshore flow through The Gorge which
began today will increase tonight and continue through at least
Tuesday. Look for more valley fog and low clouds in the nights and
mornings away from The Gorge but windy conditions in the western
gorge and in parts of the Portland and Vancouver areas. The first
system that will try to break down the upper ridge will arrive at the
coast Wednesday...with subsequent systems bringing some rain at times
the remainder of next week and next weekend.
Short term...tonight through Wednesday...clouds were generally
moving north of southwest Washington and northwest Oregon this
afternoon as an upper ridge near the coast continued to build
northward. The exception was the low clouds and patchy fog that have
cleared north of Salem but were still persisting in the south
Willamette Valley. Those are trying to clear...but not sure it will
be entirely successful. If they do successfully clear...they will
reform again fairly early this evening and then build back northward
Offshore surface pressure gradients through The Gorge have surpassed
4 mb this afternoon...and will continue to increase to 7 or 8 mb
tonight...then continue through Tuesday. This will bring winds
gusting to around 50 or 55 miles per hour at Corbett and Rooster Rock...and 65
to 75 miles per hour or so at Crown Point. This east wind event is mostly a gap
flow event...with an inversion developing near the Cascade crest.
Thus the winds will affect the western Columbia River gorge and parts
of the Portland and Vancouver metropolitan areas the most...and restrict fog
in those areas. But areas away from The Gorge will likely continue to
see night and morning fog and low clouds through Wednesday.
The air mass is quite warm above the developing inversion...and we
will likely see temperatures well up into the 60s in parts of the Coast
Range and Cascade foothills the next couple of days...and possibly
near the coast. Some areas in the valleys that do not have much fog
could get there as well.
East winds relax Tuesday night and Wednesday as the upper ridge moves
east and the first system trying to knock down the upper ridge
reaches or approaches the coast. We should still see quite a bit of
morning fog inland Wednesday morning...and perhaps some small chances
of rain along the coast as this first system weakens dramatically.
Long term...Wednesday night through Sunday...active and
more seasonable weather pattern sets up for late this week. Coast
may see some sprinkles or light rain Wednesday night into Thursday
as a frontal boundary stalls offshore. The front is finally pushed
eastward on Friday...bringing a decent chance for rain across
western Oregon and southwest Washington. Rain turns to showers
behind the front and starts to taper off late Friday into Saturday.
Saturday could be mostly dry before another system brings more rain
on Sunday. -McCoy
Aviation...increasing offshore flow has resulted in most locations
turning VFR this afternoon...with the main exception to this idea
being found in the southern Willamette Valley where IFR conditions
continue. There is a decent chance these conditions will not improve
across the southern Willamette Valley...and even if they do...keug
will likely return to IFR very quickly this evening. Otherwise...
expect increasing east winds near the mouth of the Columbia River
gorge tonight. There is a good chance the kpdx and khio will decouple
enough that they may see a several hour period of flight
restrictions...but confidence in timing and details remains rather
Kpdx and approaches...increasing east winds near the mouth of the
Columbia River gorge will bring predominantly VFR conditions to the
terminal through 00z Tuesday. However...there is a decent chance
LIFR/IFR conditions could push up the river for a several hour period
centered around 12 to 15z Monday as weak west winds likely develop
later tonight. /Neuman
Marine...a westerly swell will arrive Monday morning and push seas
into the 10 to 12 feet range. Otherwise...the next warm frontal storm
system should spread southerly wind gusts of 25 knots into the waters
late Tuesday. Several additional weak frontal storm systems may bring
periods of 25 to 30 knots winds to the waters for the second half of the
work week...but at this point...stronger winds appear unlikely.
Nonetheless...storm systems farther offshore will be sufficiently
strong enough to allow some larger westerly swells to push seas
solidly into the teens late in the work week. /Neuman
Pz...Small Craft Advisory for hazardous seas from 5 am to
9 PM PST Monday for coastal waters from Cape Shoalwater Washington
to Florence or out 60 nm.
Small Craft Advisory for rough Columbia River bar until
6 PM PST this evening.
Small Craft Advisory for rough Columbia River bar from
10 am to 9 PM PST Monday.
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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.