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Area forecast discussion 
National Weather Service Portland or
306 am PDT Wed Jul 27 2016

Synopsis...another weak upper disturbance was off the coast this
morning and will move through the Pacific northwest today, continuing
the onshore flow this morning. 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 friday)...low clouds were solid along
the coast this morning, spreading inland again especially along the
Columbia River, but a little slower than on Tuesday morning. This is
in response to the continued light westerly flow aloft and a weak
upper disturbance off the coast that will move through southwest
Washington and northwest Oregon today. Coverage of low clouds inland
today will likely be a bit less than on Monday and will clear a bit
earlier, and thus expect inland temps near or slightly above those of
Tuesday.

After that, weak flat upper ridging is expected Thursday and Friday
that will bring warming to the area. The warming will be capped by
the continued light westerly flow aloft and the induced modest
onshore flow. Look for night and morning low clouds and patchy fog to
continue along the coast, that will try to extend inland mainly along
the Columbia River but with less inland extent each morning. The net
result will be temps inland rising into the lower to mid 90s, but not
the excessive values that would have been possible if the thermal
trough was west of the Cascades versus actually being east of the
Cascades due to the onshore flow. Tolleson

Long term...no changes. Previous discussion follows...(friday night
through tuesday)...heights begin to fall Friday night as a deeper
upper level low moves from the Gulf of Alaska into southern British
Columbia. Still some disagreement among the forecast models in the
track and depth of the upper trough, but generally expect a cooler
and cloudier weekend and start to next week. Introduced a slight
chance of showers for the northwestern portion of the forecast area
early Sunday as this upper trough and associated surface front slides
across, but moisture looks quite minimal so will hold off on anything
higher than that for now. Onshore flow aloft will prevail through the
first portion of next week with another reinforcing impulse crossing
the region around Tuesday, keeping temperatures a few degrees below
seasonal norms. Cullen
&&

Aviation...based on satellite fog product imagery and surface obs,
low-MVFR or IFR stratus extends along the coast and into the coastal
gaps. Stratus is also making a slow push up the lower Columbia,
reaching just past Kelso as of 09z. Expect the stratus will push into
portions of the northern Willamette Valley, likely affecting kpdx and
kttd for at least a few hours between 12z and 18z. Expect the
interior lowlands and central coast will be clear by late morning.
The north coast, including kast, should be the slowest to clear, but
think VFR conditions are likely by 21z. The marine stratus will push
back onto at least the north coast by late this evening, potentially
holding off until after midnight along the central Oregon coast.

Kpdx and approaches...expect at least a few hours of MVFR conditions
between 12z and 18z. Then clouds clear for VFR during the rest of the
day and tonight. Northwest winds to breeze 15 to 20 kt at times late this
afternoon and this evening. Pyle
&&

Marine...a typical Summer-time northerly flow pattern to persist
through the end of the week, with surface high pres over the NE pac
and a thermal trough over the north calif and S Oregon coast. Winds are
gusting 20 to 25 kt this morning over pzz255, pzz275, and pzz270, and
a Small Craft Advisory is in effect for these zones through early
Thu. Winds will increase further this afternoon, with gusts to 25 kt
developing over pzz250. Gusts to 30 kt will be likely for areas south
of Newport. Expect the gusty wind pattern to continue through Fri.
Winds will subside somewhat over the weekend as the NE pac surface
high weakens.

The gusty winds are leading to seas dominated by short-period,
locally generated wind waves. The central Oregon waters have seen
several hours of seas around 7 ft with a dominant period of 6 to 7
seconds, so decided to issue a Small Craft Advisory for hazardous
seas this morning. An advisory for seas may be needed over the
northern waters later today or tonight. Seas remain choppy through
the remainder of the week. Overall wave heights decrease over the
weekend into the first part of next week with much lower wind-wave
component. Pyle
&&

Pqr watches/warnings/advisories...
or...none.
Washington...none.
Pz...Small Craft Advisory for winds until 5 am PDT Thursday for
coastal waters from Cascade Head to Florence or out 10 nm-
waters from Cape Shoalwater Washington to Florence or from 10 to
60 nm.

Small Craft Advisory for winds from 11 am this morning to 5 am
PDT Thursday for coastal waters from Cape Shoalwater Washington to
Cascade Head or out 10 nm.

Small Craft Advisory for hazardous seas until 5 am PDT Thursday
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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