Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 271626
AFDPQR

Area Forecast Discussion
National Weather Service Portland Oregon
925 AM PDT Tue Sep 27 2016

.SYNOPSIS...A weak front will weaken and dissipate over southwest
Washington and northwest Oregon today, but not before bringing
clouds, cooler temperatures and spotty precipitation to the area. The
forecast area will be in between systems during the mid week period.
The next low is expected to affect the area later in the week and on
next weekend, bringing more clouds, cooler temperatures, and showers
to the area, with snow possible this weekend over the higher
Cascades.
&&

.SHORT TERM...Today through Thursday...A weak front moved into
southwest Washington and northwest Oregon overnight and this morning
with clouds over a good part of the forecast area except the Cascades
south of about Detroit. Precipitation has been spotty and mainly
along the north coast and adjacent coastal mountains and in the south
Washington Cascade foothills. Suspect the precipitation will not get
much farther than that the rest of today. The front will continue to
weaken and thin out through the day with some sunshine breaking
through this afternoon. Temps should be much cooler than Monday,
falling into the 70s today in most of the valleys.

The models continue to say we will be in between systems after today,
through tonight and Wednesday and into Thursday. This should lead to
less clouds and more daytime sunshine. The models suggest we may see
some clouds form along the Cascade foothills tonight and Wednesday
morning and along the coast and coast range with less in the valleys
though there may be some local valley fog. Night and morning clouds
on Wednesday night and Thursday morning may be more confined to along
the coast and inland around the Columbia River, with some patchy fog
around again.

Temps Wednesday will again be in the 70s in the valleys. The next low
will be setting up off the coast Thursday and this will slowly cool
the air mass, causing temps to fall a couple of degrees. There is a
slight chance of some showers over the higher Cascades late Thursday
and Thursday night with the main activity in Central Oregon. Tolleson

.LONG TERM...No Changes. Previous discussion follows...
(Thursday night through Monday)...Expect increasing clouds late
Thursday night through Friday as the upper level trough advances
south and east into the far eastern Pacific just offshore. The first
round of rain will likely reach the coast by Friday afternoon, before
pushing onshore in the evening. Still some timing differences for the
various impulses rotating through the upper low, so it remains too
early to pinpoint the timing and location of heaviest rainfall
through the weekend, as well as just how much rain, but alternating
periods of steady rain and drier weather with some lingering showers
seem likely through the weekend. Another disturbance may arrive later
Sunday or early Monday. Temperatures through the extended period will
remain well below seasonal normals, only reaching the lower 60s at
best from Friday through early next week. Snow levels begin quite
high (generally above 8000 feet) on Thursday night, but quickly lower
to 5500 feet by around midday Friday and remain between 5000 and 6000
feet through the weekend. Cullen
&&

.AVIATION...MVFR stratus over much of most of the Willamette Valley
this morning will gradually lift to vfr 17-18Z and scatter out
21-22Z. clouds obscuring coast range and some of the lower cascade
slopes this morning through 19z. Front is in the dissipating stage
along the coast from TMK to ONP with mvfr and some local ifr cigs and
isolated drizzle through 18Z. Expect clouds to scatter out along the
coast after 18z. local ifr visibility in fog will expected along the
coast after 06z with mfr and local ifr stratus developing after 08z.
patchy ifr fog expected over inland valleys aft 09. There is a
possibility of some stratus developing in the southern Willamette
Valley aft 12-15z Wednesday. Schneider

KPDX AND APPROACHES...MVFR conditions will continue through 18-19z
and scatter our around 21z. Schneider
&&

.MARINE...High pressure will strengthen over the northeast Pacific
today and linger through Wednesday. This will bring small craft
advisory level northerly winds, particularly to the outer waters.
Seas should also approach hazardous sea criteria later today due to
them being especially steep and choppy.

An area of weak low pressure will move into the northeast Pacific
Friday and linger through the weekend, which should result in quieter
weather across the waters, but there could be a brief southerly surge
or two in winds. The main thing that will need to be watched is the
possibility for a developing low pressure system to impact the waters
late Sunday or Monday, possibly bringing gale force winds or higher.
Confidence in this scenario remains low due to several models not
showing this possibility at this point. /Neuman
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 3 PM PDT Wednesday for
     Waters from Cape Shoalwater WA to Florence OR from 10 to
     60 nm.

     Small Craft Advisory for hazardous seas from noon today to 9 AM
     PDT Wednesday for Coastal Waters from Cape Shoalwater WA
     to Florence OR out 60 nm.

     Small Craft Advisory for winds from noon today to 10 PM PDT
     this evening for Coastal Waters from Cape Shoalwater WA to
     Florence OR out 10 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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