Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 262145 AAA

Area Forecast Discussion
National Weather Service Portland OR
245 PM PDT Mon Jun 26 2017

.SYNOPSIS...A shortwave upper level trough is moving through SW
Washington and NW Oregon today. This feature brought thunderstorms to
portions of the fcst area this morning. There remains a slight chance
of thunderstorms in the Lane County Cascades into early this evening,
but otherwise the threat appears to be over. A dry and seasonal
pattern is expected through the rest of the week. Dry northwesterly
flow will bring near average temperatures and a pattern of morning
clouds and afternoon sunshine. Temperatures may warm a bit toward the
end of the week and early next weekend.


.SHORT TERM...Tonight through Thursday...Today is a transition day
for the weather pattern over the Pac NW. The strong upper level ridge
that brought record breaking heat over the weekend has shifted east
into the Rockies. This has opened the door for a shortwave trough to
move into the Pac NW. There were numerous elevated thunderstorms this
morning in the southerly flow ahead of the trough. As the trough has
moved onshore this afternoon, the mid-level flow has developed more
of a westerly component and the thunderstorm activity has shifted
east of the Cascades. There is still a slight chance of a
thunderstorm near the Cascade crest, mainly south of Mt. Hood,
through the early evening hours. Otherwise, it has turned into a nice
day, with temps across the region currently in the low to mid 70s, a
welcome relief from the heat of the past few days. Marine clouds
filled into most of the interior lowlands this morning, but it has
now cleared back to the coast and west slopes of the Coast Range
this afternoon. Increasing onshore flow will bring more cool marine
air into the valley later this afternoon and evening.

There will be little change to the overall weather pattern for the
next few days. A weak upper level troughing pattern will bring
continued moderate onshore flow, keeping temps near seasonal
averages. So expect highs in the mid 70s for the interior lowlands,
with 60s at the coast. The onshore flow will also bring the typical
pattern of marine stratus pushing into the lowlands during the
overnight and morning hrs, then burning back to the coast during the
afternoon and evening.

The NE Pac upper ridge is modeled to strengthen over the region on
Thu. This will likely push temps several degrees higher, with highs
rebuilding back into the upper 70s to low 80s over the interior. Pyle

.LONG TERM...Thursday night through Monday...Flat upper level ridging
is modeled to reside over the Pac NW Fri and Sat. The low level flow
remains weakly onshore, which should keep cool and partly to mostly
cloudy conditions in place at the coast. However, do not think there
will be enough onshore to bring a whole lot of clouds into the
interior on Fri or Sat mornings. With the increased sunshine and
slightly warmer air mass, expect highs for the lowlands to remain in
the low to mid 80s for the interior. An upper level shortwave is
modeled to drop into the region Sun into Mon. This should again
increase the onshore flow and strength of the marine
pushes, limiting temps back in the 70s. Pyle


.AVIATION...Onshore low level flow will continue through tonight
and Tuesday. Stratus has cleared back to the west slopes of the
coast range this afternoon with MVFR conditions continuing at the
coast and VFR inland. Convection inland has eased but there is
still a small chance of a shower until the disturbance overhead
moves east this evening. Expect MVFR cigs to return inland
probably not too long after midnight and continue through the
morning before lifting to VFR again Tuesday afternoon. The coast
will continue to be MVFR this evening through most if not all of
Tuesday, with some pockets of IFR possible later tonight and
Tuesday morning.

KPDX AND APPROACHES...VFR conditions this afternoon and evening.
A small chance of a shower with brief lower cigs. MVFR cigs
likely to return afternoon midnight tonight through Tue morning,
lifting to VFR during the afternoon on Tuesday. pt

.MARINE...Very weak lower pres over the waters will give way to
building high pres through the remainder of today and tonight
that will remain along the coast through most of the week. After
some south winds which have continued along a good part of the
Oregon coast this afternoon, this building higher pressure will
shift all winds to more northwesterly and northerly that will
continue through the week. The winds may come close to Small
Craft Advisory thresholds during the afternoon and evening on
Tuesday and Wednesday mainly in the far outer waters, but it
looks very borderline.

Seas to continue well below 10 ft for the next several days.
Currently seas are around 5 to 6 ft with a 7 to 9 second
dominant period. Seas will be somewhat choppy but does not look
like it will exceed advisory criteria. Periods will lengthen a
bit later in the week. pt

PZ...Small Craft Advisory for Rough Columbia River Bar from 6 AM to
     10 AM PDT Tuesday.



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This discussion is for Northwest Oregon and Southwest Washington
from the Cascade crest to 60 nautical miles offshore. This area is
commonly referred to as the forecast area. is the U.S. government's official web portal to all federal, state and local government web resources and services.