Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 272138

Area Forecast Discussion
National Weather Service Portland OR
238 PM PDT Thu Jul 27 2017

.SYNOPSIS...An upper level trough over the NE Pacific will maintain
onshore flow and some clouds moving inland tonight into Friday
morning. The clouds will clear in the afternoon for temperatures
warming into the 80s. An upper ridge slowly builds this weekend then
amplifies early next week for gradual lessening of the marine
influence and warmer daytime temperatures.


.SHORT TERM...Tonight through Monday...An upper level trough moves
over the west coast tonight and Friday morning continuing a deep
marine layer and the chance for marine clouds along the coast to move
inland Friday morning. Satellite imagery shows the marine stratus is
less cohesive offshore this afternoon as what was observed 24 hours
ago.  This combined with weaker offshore winds tonight should result
in less clouds for inland areas Friday morning compared to what was
observed on Thursday. This will lead to slightly warmer inland
afternoon temperatures Friday afternoon.

An upper level ridge builds over the area Friday night and Saturday
restricting the depth of the marine layer and limiting the inland
extent of marine stratus Saturday morning. Very limited clouds for
the interior and a warmer airmass will result in warmer temperatures
Saturday afternoon. However, an upper low approaching from the NW
will limit how high the 500 mb heights rise in the northern areas,
and prevent the temperatures of SW Washington and extreme NW Oregon
from warming much above the seasonal normals. Areas south of Portland
will be less influenced by the northern upper low, and have inland
temperatures reaching the upper 80s.

Less marine clouds are expected Friday night into Saturday morning as
the upper low continues to skirt by to the north. This will allow
temperatures in SW Washington and NW Oregon to warm into upper 80s to
low 90s, but otherwise expect little change in conditions for the
remainder of the Portland forecast area. Low-level onshore winds will
prevent the inland temperatures from warming much above 90 this

The upper level ridge amplifies Sunday night and Monday with 500mb
heights building to around 590 mb. Any marine clouds that form Sunday
night will be restricted to the coast Monday morning. The airmass
warms quite a bit Monday afternoon with modeled 850mb temperatures
increasing to 18-20 degC, and expect inland temperatures to warm into
the low 90s. ~TJ


.LONG TERM...Monday night through Thursday...A strong upper level
ridge remains through the end of the week. The models are in
disagreement on how much the upper level troughs approaching from the
NW will impact the ridge. This will maintain higher than normal
temperatures, and a lack of nightly marine clouds for continued above
normal temperatures. -Bishop


.AVIATION...Skies have cleared out about as expected this
afternoon. The only exception is at KONP where skies actually
went clear before inland areas this morning. Have adjusted the
TAF accordingly, but still expect stratus to fill in pretty
quickly by late this evening along the coast. This stratus is
expected to make it to KPDX and KTTD tomorrow morning, however it
is less likely the stratus will impact KHIO, KSLE, and KEUG.

KPDX AND APPROACHES...VFR conditions until stratus arrives Friday
morning around 10Z and remains for at least the first half of the
morning. /Bentley


.MARINE...High pres will remain over the NE Pacific, keeping
winds out of the north to northwest. Winds will generally peak
during the afternoon and evening hours and generally be strongest
across the waters off the central Oregon coast versus areas
farther north. Some guidance increases wind gusts to near small
craft strength in the afternoons, but any winds of this strength
will be isolated and short lived. The better chances for small
craft advisory strength northerlies will arrive later in the
weekend and into next week as the thermal trough builds up the
coast. Seas will remain short period through the weekend and into
next week, but wave heights will remain 6 feet or less. /Bentley



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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.