Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 261617
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
917 AM PDT Tue Jul 26 2016

.SYNOPSIS...A weak upper trough near the coast with a weak westerly
flow aloft over the Pacific Northwest will continue today into early
Wednesday with morning low clouds giving way to afternoon sunshine
and seasonable afternoon temperatures. An 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 and increase clouds over the weekend.
&&

.SHORT TERM...(Today through Thursday)...Stratus deck starting to
show signs of conversion into a stratocumulus deck inland with
stratus retreat already beginning along the coast. Inland
stratocumulus deck expected to scatter out around 19Z according to
local stratus breakout program. By mid afternoon, expect sunny skies
at most locations with Astoria and the Long Beach peninsula being the
last locations for the skies to clear. /Bentley

Previous discussion follows...
The models show one last weak disturbance currently out near 40n/140w
moving through southwest Washington and northwest Oregon later
tonight and Wednesday morning. This should spread more low clouds
onshore again Wednesday morning especially in the north, but coverage
in the south is forecast to be a bit less. The models suggest pretty
good clearing again Wednesday afternoon with some lingering low
clouds along the north coast. The air mass warms a touch Wednesday
and expect temps to warm close to those of Sunday and Monday in the
south valley and approach those values in the north valley.

The upper ridge builds some by Thursday with less coverage of morning
low clouds Thursday morning, mainly north coast and locally inland
along the Columbia River. The models indicate we have a good chance
of seeing the first of a two day stretch of low to mid 90s inland on
Thursday. Tolleson

.LONG TERM...(Thursday night through Monday)...The models are showing
one more very warm day on Friday but now with temps similar to those
on Thursday, perhaps not quite as hot as previously thought as
westerly flow continues and ridging is not quite as pronounced. The
models are continuing to show an upper trough beginning to drop down
the B.C. coast Saturday and swing through the Pacific Northwest
Sunday and early next week. The ECMWF continues to be the weaker
model with this pattern, but is getting closer to the GFS while the
GFS is not quite as strong as it had been. This convergence of the
models lends increasing confidence in a cool down this weekend,
perhaps with some drizzle near the coast by Sunday. We will have to
see whether we can sneak any showers out of this pattern early next
week. Tolleson
&&

.AVIATION...Stronger marine surge overnight and this morning
compared to the past couple of days. Widespread MVFR along the
coast and coastal valleys as of 15Z. MVFR cigs also cover much of
the SW Washington lowlands, especially along the Columbia River.
MVFR conditions extend south along Interstate 5 to KSLE. The South
Washington and North Oregon coast likely to remain MVFR through
tonight. Central Oregon Coast expected to improve to VFR in the
early afternoon, but MVFR conditions will return by this evening.
Inland areas to improve to VFR by 19Z, with areas from KPDX to
KKLS clearing latest. Guidance suggests MVFR cigs return to KKLS
and the Lower Columbia around 08Z Wed.

KPDX AND APPROACHES...MVFR at the terminal and vicinity. Stratus
expected to dissipate around 19Z. There is a high probability that
MVFR conditions will return around sunrise Wed. Weishaar

&&

.MARINE...No changes to the current forecast. However, a couple of
things to watch in the short term. Latest guidance shows
increasing boundary layer wind speeds today, with 20 to 25 kt
speeds developing over PZZ255 and PZZ275 by this afternoon. Latest
models also show 975 mb speeds to 25 kt over the south half of
PZZ270 mid to late afternoon. For now, will maintain the current
small craft wind advisory for the Central Oregon waters. However,
there may be a need to extend it into the north waters.

Models in general agreement indicating slightly stronger North
wind Wed. Will likely need a small craft wind advisory for all
waters and will look at that more closely for the afternoon
forecast. Overall pattern to remain virtually unchanged Thu
and Fri. The next upper trough is expected to swing across the
area this weekend, which will deepen the marine layer and reduce
wind speeds.

Seas expected to hover around 6 ft through tonight, with long
enough periods to avoid the square-sea condition. Spectral
analysis for buoy 029 indicates a new round of fresh swell with a
7-8 second period developing late tonight. There is the potential
for very steep, choppy conditions late tonight or Wed morning
requiring a small craft advisory for hazardous seas. Weishaar

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds from 3 PM this afternoon to 4 AM
     PDT Wednesday 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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