Area Forecast Discussion
Issued by NWS Portland, OR

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431
FXUS66 KPQR 272147
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
246 PM PDT Wed Jul 27 2016

.SYNOPSIS...Weak upper ridging will bring a two day warm spell to
southwest Washington and northwest Oregon Thursday and Friday with
inland temps around 10 degrees above normal, capped by light westerly
flow aloft and continued light onshore flow. The models continue to
indicate that an upper trough will settle southward along the coast
this weekend and early next week for cooler temps, more night and
morning low clouds, and perhaps a little drizzle or showers mainly
near the coast.
&&

.SHORT TERM...(Today through Saturday)...Heights have begun to build
across the area as a flat ridge strengthens over the Pacific NW for
the second half of the workweek. This will lead to a persistent
pattern of morning coastal clouds burning off the coast by mid day,
warm temperatures, and northerly winds. Subsidence aloft will
compress the marine layer enough to keep inland stratus intrusion at
bay Thursday and Friday morning. If anything does form in the
Willamette Valley, expect it to be scattered in nature.

High temperatures in the low 90s inland are still looking like a safe
bet, especially if skies are mostly clear tomorrow morning as
expected.

Heights will begin to fall by Friday Night as an upper low drops
south out of the Gulf of Alaska and towards British Columbia. This
will mark the end of the warm spell with temperatures returning to
near normal into the long term period. /Bentley

.LONG TERM...(Saturday Night through Wednesday)...Near normal
temperatures will continue through the long term period as model
consensus has converged on a general troughiness pattern across the
Pacific NW. These passing troughs will act to increase cloudiness in
the area, but will produce little precipitation due to the better
forcing further north and relatively high heights. /Bentley

&&

.AVIATION...Marine layer south of KTMK had pushed back to just
off the beaches early this afternoon, but has shown signs of
creeping inland along the central Oregon coast early this
afternoon. VFR across the region, except for low-end MVFR along
the South Washington coast and North Oregon coast from KTMK to
KAST. Latest guidance shows less coverage inland overnight through
Thu morning. Coastal TAF sites will be low-end MVFR of high-end
IFR through at least 18Z Thu.

KPDX AND APPROACHES...Local stratus break out tool did quite well
with the stratus dissipation this morning. Do not expect much, if
any, marine stratus Thu morning. Weishaar

&&

.MARINE...Surface high pres will persist over the NE Pac through
the end of the week, with some degree of a thermal trough over
the N Calif and S Oregon coast. Wind gusts close to 35 kt possible
through early evening over far southern PZZ255 and PZZ275. Little
change in the pattern Thu through Fri. Have extended the small
craft wind advisory until 12Z Fri for all zones except PZZ250.
Wind will ease in the north inner waters tonight, but return to
small craft advisory thresholds Thu afternoon. Wind speeds will
subside somewhat over the weekend as the NE Pac surface high
weakens.

The gusty wind is resulting in seas dominated by short-period,
locally generated wind waves. Spectral wave analysis for buoy 029
shows two primary wave energy peaks, centered around 7 seconds.
The difference between peaks is about 1 sec, which makes it hard
to distinguish between fresh swell and wind wave. Will carry
nearly all wind wave for the overall wave heights with a minimal
residual background swell. Question remains whether to include
PZZ250 and PZZ270 in the small craft advisory for hazardous seas.
Overall wave heights expected to hover around 5-7 feet with
a dominant period of 8 seconds. PZZ270 has the best potential for
square-sea conditions, but will hold off on advisory issuance for
now. Wave heights forecast to increase a foot or two late Thu or
Thu night, which would necessitate a hazardous seas advisory.
Total wave heights decrease over the weekend into the first part
of next week with much lower wind-wave component. Weishaar

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 5 AM PDT Friday for
     Coastal waters from Cascade Head to Florence OR out 10 nm-
     Waters from Cape Shoalwater WA to Florence OR from 10 to
     60 nm.

     Small Craft Advisory for winds until midnight PDT tonight for
     Coastal waters from Cape Shoalwater WA to Cascade Head OR
     out 10 nm.

     Small Craft Advisory for winds from 1 PM to 11 PM PDT Thursday
     for Coastal waters from Cape Shoalwater WA to Cascade Head
     OR out 10 nm.

     Small Craft Advisory for hazardous seas until 5 AM PDT Friday
     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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