Area Forecast Discussion
Issued by NWS Portland, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
460
FXUS66 KPQR 250352
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
852 PM PDT Sun Jul 24 2016

.SYNOPSIS...A weak upper trough near the coast Sunday with a weak
westerly flow aloft over the Pacific Northwest will continue through
through Monday and Tuesday. Expect morning low clouds giving way to
afternoon sunshine and seasonable afternoon temperatures. 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, before the
next trough arrives to moderate temperatures next weekend.
&&

.SHORT TERM...(Tonight through Wednesday)...Satellite showed some
clouds clinging to the central Oregon coast and redeveloping along
the north OR coast this evening, while inland skies were clear.
Surface onshore flow continued, with pres gradients a little
stronger than 24 hours ago. Aloft weak troughiness had developed
today, all of which favor seeing as much or a little more clouds
developing inland than that seen Sun morning. With the trough aloft,
will also continue with a chance for drizzle along the coast towards
morning. Expect marine air Mon morning to be shallow though, so
should see clouds clear back to the coast for plenty of afternoon
sunshine and temps near normal.

Remainder of short term discussion unchanged...The push Tuesday
morning looks to be a little stronger and deeper, so expect that the
clouds will linger a few hours longer and also limit some of the
heating - particularly across the northern half of the area. This,
along with lowering heights as the trough moves across the area,
will leave Tuesday as likely the coolest day in the short term
period.

Upper level high pressure then begins to build over the region late
Tuesday. Expect the surface winds slightly onshore across the
northern half of the forecast area, but with models suggesting the
surface ridge axis aligned southwest to northeast, expect more
northerly to light offshore wind component for the central Oregon
coastal areas. Thus, have tapered back cloud cover for the inland and
southern coastal zones on Wednesday, though some shallow marine
clouds may make it along the Columbia River to around Kelso. 500 mb
heights are modeled to lift to 590 dam by Wednesday afternoon, with
850 mb temperatures increasing to 16-18 degrees C. With only shallow
if any morning stratus, there will be effective warming, allowing
this to translate to afternoon maximum temperatures in the interior
reaching well into the upper 80s on Wednesday. Cullen

.LONG TERM...(Wednesday night through Sunday)...No changes. Previous
discussion follows. Models continue to show weak upper level ridging
over the Pac NW late next week. This will bring the typical pattern
of morning clouds and afternoon sun, with temps in the interior
rising into the mid 90s on Friday. Onshore flow looks to increase
next weekend as an upper level trough moves over the region. This
will bring more clouds to the interior and provide for a slight
cooling trend on Saturday and Sunday.

The threat of showers through the long term period remains near zero.
However, the GFS continues to show the potential for some monsoonal
moisture streaming north on Saturday. This could produce some
isolated dry thunderstorms in the Cascades, but confidence is low.
/64

&&

.AVIATION...VFR prevailing across the area this evening with the
exception of the coastline where low MVFR to IFR CIGS continue to
fill in. 00Z NAM and GFS indicates a weak southwest marine push
tonight compared to a northwesterly push on Sunday. With a
deepening marine layer tonight and existing dewpoints 55 to 60F
should see areas of MVFR CIGS inland late tonight through about
mid to late Monday morning then improving to VFR. Expect coastal
areas to remain MVFR through the TAF period.

KPDX AND APPROACHES...VFR conditions then MVFR cigs return Monday
morning around 15z with clearing around 17 or 18z. TJ

&&

.MARINE...There is a persistent summer-time weather pattern as
high pressure holds over the waters and low pressure remains over
N CA and S OR. The thermal trough over CA will expand north in the
afternoons and evenings for increased gusty winds in the
afternoons and evenings. The winds have eased this evening over
the nearshore zones so have dropped the advisory. Expect advisory
winds to continue over the waters 20 to 60 nm through late
tonight. Models still indicating marginal small craft conditions
Monday evening. The seas are primarily wind-driven and steep with
little influence of distant-sourced swells. There will be little
change in the weather pattern Tue and Wed. There is a chance for
stronger winds and larger steep seas Thu and Fri. TJ

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until midnight PDT tonight for
     Waters from Cape Shoalwater WA to Cascade Head OR from 10
     to 60 nm.

     Small Craft Advisory for winds until 3 AM PDT Monday for Waters
     from Cascade Head to Florence OR from 10 to 60 nm.

&&

$$

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland

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.



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.