Area Forecast Discussion
Issued by NWS Portland, OR
FXUS66 KPQR 240342
Area Forecast Discussion
National Weather Service Portland OR
843 PM PDT Sat Jul 23 2016
.SYNOPSIS...A weak upper trough will develop near the coast Sunday
and flatten the flow over the region Monday and Tuesday, bringing
slight cooling and increasing low clouds inland Monday and Tuesday
mornings than on Sunday morning, along with some patchy morning
drizzle along the coast. After Tuesday, a stronger upper level ridge
will build for the second half of the week and bring inland highs
well into the 90s Thursday and Friday.
.SHORT TERM...(Tonight through Tuesday)...The remaining marine
clouds over sw WA and extreme nw OR continued to slowly dissipate
through early evening. With the surface ridge extending inland over
western WA this evening and models indicating it should remain there
overnight, expect marine clouds to redevelop late tonight into Sun
morning, at least across the north where nw onshore winds were still
around 10 kt through 03Z. Further south northerly winds make the
likelihood of seeing marine clouds in the morning a little more
iffy, although both wrf arw and nam12 both suggest enough boundary
layer remains for clouds to redevelop. Whatever does develop
however, is likely to be more short-lived than todays clouds, so
with warmer h8 model h8 temps forecast, highs Sunday will warm some.
Remainder of short term discussion unchanged...A weak upper trough
developing on the coast Sunday will increase onshore flow later in
the day Sunday with a decent surge of low clouds inland both along
the Columbia River and also through the southern coastal gaps into
the southern Willamette Valley for Monday morning. May also see some
light patchy drizzle along the coastal areas in association with
this upper level trough. Little change on Tuesday, with morning
clouds inland giving way to seasonable temperatures and mostly sunny
afternoons. However, clouds may be a bit more persistent near and
along the coast, with possible patchy drizzle at times though no
accumulating precipitation is expected. Cullen
.LONG TERM...(Tuesday night through Saturday)...No changes.
Previous discussion follows. A weak upper level ridge will dominate
most of the long term forecast. This will bring the familiar pattern
of morning clouds and afternoon sun, with temps in the interior
rising into the 90s late next week. Some relief is possible late
next week as models continue to show an increase in onshore flow.
It is worth noting that today`s 12Z GFS is showing some monsoonal
moisture streaming north on Saturday. If this pans out we could see
some thunderstorms develop in the Cascades, but confidence is low so
will leave it out of the forecast for now. /64
.AVIATION...VFR across the area this evening. Clouds cleared more
than anticipated along the north Oregon and south Washington
coast. Model RH fields indicating MVFR cigs redeveloping late
tonight and early Sunday morning at the coast and then inland.
Fairly confident CIGS will develop along the coast and inland
north of about KSLE, but less so south of KSLE. The overall
marine layer tonight through Sunday morning should be less deep
and not as extensive so will dissipate sooner Sunday, with VFR
all areas by late morning. Coastal winds will be increasing gusty
starting late Sunday morning. Gusts to 25 kt likely along the
coastline during the afternoon through early evening hours.
KPDX AND APPROACHES...VFR conditions through 12Z Sunday then MVFR
CIGS between 1500 and 2500 feet expected to return. Where cloud
develop should clear around 17-18Z. Likely to have some gusty
Northwest wind late this afternoon into the evening hours.
.MARINE...Main marine issue will be wind. Will maintain the small
craft advisory for wind across zones PZZ255 and PZZ275 through 09Z
Sun. Then pickup again later Sunday morning then spreading into
the north zones Sunday afternoon. May not need a small craft wind
advisory Monday as models show a weak impulse moving north of the
area, deepening the marine layer. However 00Z models show near small
craft advisory conditions for the PZZ255 and PZZ275 zones Monday
afternoon and evening. Upper ridge strengthens Tue, which allows
for a stronger surface gradient. Thus, will likely see 25-30 kt
wind gusts over PZZ255 and PZZ275 Tue afternoon. Typical summer
pattern continues the latter half of next week for continued small
craft advisory wind conditions in the afternoon and evening hours.
Overall wave heights to hover in the 4 to 5 foot range through
early next week. Highest wave heights over the south waters where
wind waves are larger. As is typical for this time of year, sea
state to be dominated by wind wave and/or fresh swell. Wave heights
show a steady increase the latter half of next week, possibly
reaching 7 to 8 feet. mh Weishaar
PZ...Small Craft Advisory for winds from 2 PM Sunday to midnight PDT
Sunday night for Coastal Waters from Cape Shoalwater WA to
Cascade Head OR out 60 nm.
Small Craft Advisory for winds until 2 AM PDT Sunday for
Coastal Waters from Cascade Head OR to Florence OR out 60
Small Craft Advisory for winds from noon Sunday to 3 AM PDT
Monday 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.