Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 230942
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
241 AM PDT Sat Jul 23 2016

.SYNOPSIS...The upper level low from Friday has moved east of
southwest Washington and northwest Oregon early this morning, but
weakly cyclonic northwest flow aloft will maintain some onshore flow
under weakly rising 500 mb heights today. A very weak upper trough
will develop near the coast Sunday that will continue Monday and
Tuesday that will bring slight cooling again with a bit more low
clouds inland Monday and Tuesday mornings than on Sunday morning, and
with some patchy morning mainly coastal drizzle. After Tuesday upper
ridging will bring warming from Wednesday through Friday, with highs
inland likely reaching at least the mid 90s especially Thursday and
Friday. Temps may start to fall next weekend as the upper ridge
weakens.
&&

.SHORT TERM...(Today through Monday)...The upper low from Friday has
moved well east this morning, but has left weakly cyclonic west to
northwest flow aloft in its wake that is allowing a fairly deep
marine inversion to remain over southwest Washington and northwest
Oregon. This is allowing higher stratocumulus to spread south along
the Cascade foothills and the coast range this morning, and if the
models are right, which could fill most of the inland valleys this
morning. The Langley Hill National Weather Service Doppler radar has
been showing some weak low level echoes not unlike the QPF pattern on
the models, so will hold onto some patchy drizzle this morning along
the north coast that could extend locally inland in the north early
this morning. 500 mb heights do rise some this afternoon under weak
subsidence so expect decent clearing this afternoon as our forecast
area is mostly south of the surface ridge axis at that point.
Overall, expect inland temps up a few degrees this afternoon versus
those from Friday.

The models do show a very weak saggy/baggy upper trough developing
along the Oregon coast on Sunday. Morning low clouds will probably be
a little less extensive Sunday morning than this morning, and this
could allow inland temps to reach the mid 80s inland Sunday
afternoon. But the weak upper trough induces a bit more onshore flow
and the models indicate a decent surge of low clouds inland both
along the Columbia River and also through the southern coastal gap
into the Southern Willamette Valley Monday morning. This is indicated
to start a slight cooling trend Monday with perhaps some patchy
drizzle near the coast. Tolleson

.LONG TERM...(Monday night through Friday)...The weak saggy/baggy
upper trough lingers over southwest Washington and northwest Oregon
on Tuesday, and the models suggest Tuesday will be the coolest day of
the week with highs near or slightly below normal with some patchy
drizzle near the coast. After that, the upper ridge rebuilds, peaking
Thursday and Friday, with highs into at least the low to mid 90s
inland. The models suggest onshore flow may redevelop next weekend
for a bit of relief. Tolleson
&&

.AVIATION...Primarily VFR conditions across the area so far. We are
seeing mvfr stratus develop along the eastern slopes of the Coast
Range which occasionally has drifted in and out of KSLE and KEUG.
Cigs with this stratus generally 2500-3000 ft. With shortwave moving
across the area this morning, will likely see stratus solidify
southward along the Coast, with cigs around 2500 ft, as well as some
occasional drizzle, mainly further north including KAST, which can
already be seen on Langley radar. Shortwave will also help the
stratus with cigs around 2500 ft along the east side of the Coast
Range spread eastward into at least the northern terminals, with less
confidence further south at KSLE and KEUG. Cigs should break up
around 18z inland, with VFR cigs through the rest of this afternoon
and evening. Along the Coast will probably see KONP improve to VFR
fairly early, while further north at KAST will hold on to MVFR
stratus until around 20z, for VFR conditions through the rest of this
afternoon and early evening.

KPDX AND APPROACHES...VFR conditions to continue until around 12Z
when MVFR stratus will spread eastward into the terminal. Conditions
should improve to VFR by 18Z as stratus breaks up, with VFR
conditions this afternoon and evening. -McCoy
&&

.MARINE...Typical summer-time pattern, with high pres over the NE
Pacific and a thermal trough over N California. This pattern remains
in place through most of next week. This means gusty northerly winds
over the waters, particularly during the afternoon and evening hours.
Have small craft advisory for winds for the central OR waters from
mid afternoon today through 2am Sunday, with gusts to 25 kt expected.
Will likely need small craft advisories for winds again on Sunday
afternoon and evening, and also much of next week.

Seas generally around 3 to 4 ft this morning will build to 4 to 6 ft
this afternoon, with higher seas south of Newport where winds are
stronger. Will generally see wind-driven seas around 4 to 6 ft
through Sunday and Monday. Seas build up into the 7 to 9 ft range
midweek through late next week. This may require small craft
advisories for hazardous seas, as wave periods will be around 7 to 9
seconds. -McCoy
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds from 3 PM this afternoon to 2 AM
     PDT Sunday for Coastal Waters from Cascade Head OR to
     Florence OR out 60 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.


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