Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 111005

Area Forecast Discussion
National Weather Service Portland OR
252 AM PDT Tue May 11 2021

.SYNOPSIS...Upper level high pressure will result in dry weather and
above average temperatures for much of the next week. The next
significant storm system appears most likely to arrive early next


.SHORT TERM...Today through Thursday...Models are in good agreement a
low amplitude shortwave ridge will traverse the Pacific Northwest
today before flattening Wednesday ahead of a weak shortwave trough
dropping southeastward across the region late Thursday. The end
result is that the region will remain dry, though. Coastal high
temperatures should remain near 60F and inland high temperatures
should climb well into the 70s through Thursday with a few spots in
the Willamette Valley topping out near 80F Wednesday. The low level
flow does back a little Wednesday into Thursday so morning marine
clouds should become more prevalent along the coast and lower
Columbia River during this time. /Neuman

.LONG TERM...Thursday night through Tuesday...Models and their
ensembles are in good agreement the aforementioned shortwave trough
will dive southeastward into the Desert SW late Thursday through
Saturday. This will result in a sharper shortwave ridge building
back across the Pacific Northwest Saturday into Sunday. This will
keep the area dry with high temperatures topping out in the 70s to
low 80s for inland locations. Models and their ensembles do loosely
agree another shortwave trough with more cold air aloft and better
dynamics will approach the region early next week. There are still
major differences in the timing and amplitude of the shortwave
trough, though. In addition, approximately 20% of the ensembles
suggest the area will remain dominated by a shortwave ridge through
early next week. Given all of this, trying to time out when rain
will fall...i.e. Sunday night, Monday, Monday night, Tuesday, still a low confidence forecast at best at this point so
PoPs and temperatures remain in line with NBM guidance. /Neuman


.AVIATION...High pressure aloft continues to dominate across the
region resulting in northwesterly flow at the surface. Moist
onshore flow, with temp and dew points getting closer, will
likely result in some MVFR conditions along the coast developing
around 12Z Tuesday. Elsewhere, the likelihood of MVFR or lower
conditions developing is much lower, but can`t rule out the
possibility of some patchy cigs developing along the foothills of
the Cascades and Coast range. All areas will return to VFR after
18Z Tuesday through the remainder of the period. Possibility of
locally breezy northerly winds between 18Z Tuesday and 06Z
Wednesday across the region, but should dissipate as night nears.

For detailed regional Pac NW aviation weather information, go online

KPDX AND APPROACHES...VFR conditions prevailing, with a low
probability of some MVFR conditions developing after 12Z
Tuesday. VFR conditions expected to return by 18Z Tuesday.
Locally breezy winds possible from 18Z Tuesday through 06Z
Wednesday but should not exceed 20kt. /42


.MARINE...Minimal change expected in overall conditions through
Friday as high pressure will continue to be the dominant feature
over the coastal waters. At the same time, a surface thermally
induced trough will persist from northwest CA to the south OR
coast, which will cause a prolonged period of northerly winds
over the waters. Expect winds to be strongest during the
afternoon and evening hours. Have extended the current Small
Craft Advisory for PZZ255 & PZZ275 through Wednesday morning.
Have also issued a Small Craft Advisory for PZZ270 & PZZ250
starting this afternoon through the evening hours, with the
highest gusts south of Tillamook Head. In addition to the winds,
seas will be fairly choppy of the central coastal waters next
couple of days.


PZ...Small Craft Advisory from 11 AM this morning to 11 PM PDT this
     evening for coastal waters from Cape Shoalwater WA to
     Cascade Head OR out 60 NM.

     Small Craft Advisory until 8 AM PDT Wednesday for coastal
     waters from Cascade Head OR to Florence OR out 60 NM.



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