Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 082120

Area Forecast Discussion
National Weather Service Portland OR
220 PM PDT Sat Aug 8 2020

.SYNOPSIS...Warmer weather and more sun returns Sunday and Monday as
a weak ridge of high pressure moves across the Pacific Northwest.
Milder temperatures then follow for the rest of the coming week as a
weak upper level trough slowly moves through.


.SHORT TERM...Tonight through Tuesday...Still some marine clouds
were seen in visible satellite pictures early Saturday afternoon
over the northern and coastal parts of the forecast area. Water
vapor pictures showed the upper trough crossing the Cascades and
moving east. Models remain in good agreement showing a weak ridge
aloft passing over the region Sunday and Sunday night, while a
thermal induced surface trough along the south Oregon coast turns
the low level flow more northerly. Resulting low level drying will
likely limit most of the low level clouds to coastal areas through
Sunday night while temperatures begin to warm again.

Monday onshore flow begins to strengthen again late in the day as
the upper flow flattens out and heights slowly fall. The
strengthening onshore flow though is likely to kick in too late to
have much of an impact on inland temperatures beyond the lower
Columbia valley, as model 850 mb temperatures still peak on Monday
in the range of 16C to 18C, enough to carry high temperatures in the
upper 80s, with a couple of 90F readings still possible especially
in the south Willamette Valley. Monday night and Tuesday will bring
a return of marine air for cooler temperatures closer to the
seasonal normals.

.LONG TERM...Tuesday night through Saturday...Models in general
agreement in showing a broad upper trough moving across the Pacific
Northwest during the coming week. Overall impressions are that the
trough is not likely deep enough to bring much of a threat of
showers to the region, but low level onshore flow will bring some
diurnal clouds mainly to the coast and north interior along with
temperatures a little cooler than normal through the end of the
week. 12Z EC operational run is most bullish on showers Thursday
into Thursday night, and given some support from some ensemble
members, will keep a slight chance for showers then over southwest
Washington. Friday into Saturday models have generally push the
trough off to the east with some ridging aloft following it, so
expect dry weather with warming temperatures.


.AVIATION...A weak upper level disturbance continues to slowly
move across the area. Low level flow will bring a return of low
end VFR/high end MVFR cigs along the coast this evening and into
Sunday morning.

For inland areas, VFR with cigs between 5000 and 8000 ft. Expect
some gustier north/northwesterly winds through the valley near
20 kt through 12Z Sunday. Coastal airports, expect gusty
northerly winds near 20 kt to persist through 12Z Sunday.
However, KONP could see gusts up to 30 kt through this same time

KPDX and APPROACHES...VFR with cigs 5000 to 8000 ft.
Northwest with gusts 15 to 20 kt through 06Z Sunday likely. /42


.MARINE...High pressure continues across the waters through
early next week with an thermally induced trough developing over
the far south Oregon coast through Sunday. North winds will
increase to 15 to 25 kt with gusts up to 30 kt and seas 7 to 10
feet at 13 seconds this afternoon. Gusts of 30 kt possible south
of Cascade Head, with these higher gusts becoming more prevalent
with daytime heating. Nearshore winds will be strongest through
Saturday and Sunday afternoon and evening, but will likely drop
below 20 kt during the night and into the morning hours.

Small craft conditions will likely persist into early next week.
Will see winds weaken with gusts to 25 kt Monday afternoon
before easing below small craft criteria Tuesday morning. Seas
will remain elevated, but will start to subside by Wednesday.

The remainder of next week looks to be rather benign with seas
around 4 to 6 ft and gusts below 15 kt. /42


PZ...Small Craft Advisory until 11 PM PDT Sunday for coastal waters
     from Cape Shoalwater WA to Florence OR out 60 NM.



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