Area Forecast Discussion
Issued by NWS Portland, OR
FXUS66 KPQR 290322
Area Forecast Discussion
National Weather Service Portland OR
820 PM PDT Thu Jul 28 2016
.SYNOPSIS...Weak upper ridging will keep inland temperatures high
through Friday. An upper level trough will increase night and
morning clouds and cooler temperatures this weekend. Brief high
pressure will move over the area Monday before another upper low
impacts the clouds and temperatures Tuesday and Wednesday.
.SHORT TERM...(Today through Sunday)...Today`s highs reached the
lower to mid 90s inland, with Hood River leading the pack with a high
of 99F. Stratus which eroded along the North Oregon/South Washington
Coast today has redeveloped. We will see stratus overnight stay
mainly confined to the Coast and up the Columbia River to Kelso.
No changes to rest of discussion. Previous discussion
follows...Tomorrow`s highs should be ~1 to 2 degrees cooler than
today as heights fall and temps aloft cool slightly (<1C). In
addition, have cooler marine influence air a bit further inland
tomorrow as the thermal trough shifts eastward.
Brief period of warmer than normal temps comes to an end on Saturday
as a longwave trough starts to dig across the Pacific NW. Through the
short term period, this will only act to increase cloud cover and
cool temps to near normal. The only sensible weather impacts from
this trough in the short term period will be the potential for some
drizzle to be squeezed out of the marine layer along the coast and
slightly inland in NW Oregon and SW Washington both Saturday and
Sunday morning. -McCoy/Bentley
.LONG TERM...(Sunday Night through Thursday)...No changes. Previous
discussion follows...Models are coming into better agreement on an
upper low moving through Washington on Monday night and Tuesday. It
appears this low will drop far enough equatorward to bring the
potential for rain showers for northern Oregon and southwest
Washington. Therefore, introduced a slight chance PoP for these
northern areas Monday evening. Was hesitant to go much higher with
the PoPs as there has been a tendency for these waves to be less
amplified/further north through time and would not be surprised if a
similar trend begins with this wave. With that being said, with
models in good agreement on timing and strength of the wave, felt a
slight chance was justified. Do expect diurnal cu development along
the Cascade crests on Monday afternoon, but with a fairly shallow
convective cloud depth, do not anticipate any showers to develop.
Shortwave ridging will build in behind this low and bring fair
weather for the middle portion of next week. Beyond this, fair
weather will prevail for the remainder of the long term period.
ECMWF/GFS/GEM are all hinting at another upper low dropping down the
BC coast towards next weekend, but considerable differences remain
with regard to the timing and southern progression of this system.
.AVIATION...Stratus with IFR conditions were hugging the coast
this evening, with clear skies and VFR conditions inland. Stratus
expected to make only a weak push inland tonight...mainly up the
lower Columbia Valley to vcnty of KKLS. This is likely to bring IFR
cigs back to KAST that will last through about 18Z Fri. Along the
central coast near KONP, stratus is not expected to move inland
much, similar to last night. It is likely that KONP will return to
IFR conditions, but there remains about a 40 percent chance that
KONP could see intervals with VFR conditions tonight and Fri
morning. Along the coast VFR conditions become likely after 18Z.
KPDX AND APPROACHES...VFR tonight and Friday.
.MARINE...Surface high pres to persist over the NE Pacific for at
least the next few days. This will continue the typical summertime
pattern of gusty north wind over the coastal waters. The strongest
winds will continue to be over the southern waters, and the northern
outer waters where gusts to 30 kt are possible mainly during the
afternoon and evening hours Friday. A small craft advisory for wind
remains in effect for all but the northern inners waters through 12Z
Saturday. Will allow the northern inner waters small craft advisory
for winds to expire at 11 pm tonight. Overall, wind speeds still
expected to gradually subside over the weekend, especially Saturday
night and Sunday, as the NE Pac surface high weakens.
With north winds continuing for the next few days, seas will
continue to be dominated by steep locally generated seas. Will need
to hang on to the small craft for hazardous seas through Fri night
for the northern and outer waters due to square seas in the range of
7 to 9 feet. Locally driven wind waves will start to subside Sat as
wind speeds diminish, but a fresh swell from the nnw will keep seas
PZ...Small Craft Advisory for winds until 5 AM PDT Saturday for
Coastal waters from Cascade Head to Florence OR out 10 nm-
Waters from Cape Shoalwater WA to Florence OR from 10 to
Small Craft Advisory for hazardous seas until 5 AM PDT Saturday
for Coastal waters from Cascade Head to Florence OR out 10
nm-Waters from Cape Shoalwater WA to Florence OR from 10
to 60 nm.
Small Craft Advisory for winds until 11 PM PDT this evening for
Coastal waters from Cape Shoalwater WA to Cascade Head OR
out 10 nm.
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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.