Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 242111

Area Forecast Discussion
National Weather Service Portland Oregon
203 PM PDT Mon Oct 24 2016

.SYNOPSIS...Strong low pressure well off the Washington
coast with an associated cold front trailing back over western
Washington and Oregon. This front will move slowly east across
western Oregon and Washington this evening. Showers will develop in
the unstable air behind the front. This system will bring gusty south
to southeast winds and large surf to the coast today through Tuesday.
The broad low will weaken and move north tonight and Tuesday. Another
low is expected to take its place Tuesday night and Wednesday. This
next low will push a warm front across the region from the south
Tuesday night and Wednesday morning bringing more significant
rainfall. Gusty winds will likely accompany this system along the
coast on Wednesday. The area will remain under the influence of a
broad upper trough with generally wet and showery weather throughout
the week.


.SHORT TERM...Today through Wednesday...Mature surface low around
968mb about 260mi west of Hoquiam moving slowly north. This low will
weaken tonight and continue to move north. The associated cold front
is over the Washington and Oregon coast and will move inland during
the evening. Occluded front is wrapping back around the low and
associated with storm force winds, which are well offshore of Oregon
and Washington Coastal waters this afternoon. The strong easterly
gradients over the coast will help confine the strongest winds to the
waters and not generally over the coastal communities. Still, it will
be windy along the coast this evening.Expect a few higher gusts at
the exposed headlands, otherwise impact should not be too great and
for now we will not have any warnings for high wind over the land. At
this time we expect the northward motion of the low to continue as
the system begins to slowly weaken this evening.

Winds over the inland valleys are not expected to be a real problem
today as no significant north south gradient develops, but it will
be a breezy. Gusty east winds will continue through he Columbia
Gorge and extending.

The front will be followed by cooler air aloft later tonight and
since it is fairly warm at the surface and there is a good amount of
vertical shear a few thunderstorms are expected to develop over the
waters and along the coast.

Showers will likely redevelop along the coast Tuesday morning but
inland areas will be mostly dry with a chance of showers. Models are
in fair agreement that a surface wave off northern California will
move north and develop into a closed surface low late Tuesday night.
and Wednesday morning. This system will send a fairly strong warm
front over the area. Precipitable water values and lift along the
frontal zone are a good indication of a fairly wet warm frontal
passage on Wednesday. This will be followed by a the system`s cold
front later Wednesday. Models indicate that that front could stall
turning into a mostly stationary front with periods of rain
continuing over western Oregon and Washington overnight then moving
east on Thursday.  Schneider

.LONG TERM...Thursday night through Monday...Wet weather pattern
looks to continue into this weekend, with another trough dropping
out of the Gulf of Alaska Thursday into Friday. May get a brief
break from the rain Friday morning as shortwave ridging builds up
ahead of the next surface Low that comes up from the southwest. This
Low looks fairly weak, bottoming out in the high 990s to right
around 1000 mb. Heavier rain will impact southwest Oregon, but
should be more moderate as it moves farther north into Northwest
Oregon and Southwest Washington. Showers should linger across the
area Saturday night through Sunday morning before another weak
system comes up the same track as the last Low, along the track of
the south side of the upper-level trough sitting off the coast of
Washington and Oregon. This one looks fairly weak as well, only
bringing moderate rainfall to our area Sunday evening through Monday
morning. This second surface low is more associated with the upper-
level trough, which shifts onshore Sunday night into Monday, though
another upper-level trough appears to come in and take its place off
the coast of Washington and Oregon for on-and-off rainy weather to
continue into early next week. -McCoy

.AVIATION...Primarily VFR conditions over the interior tonight
through 18z Tue morning. Areas of MVFR cigs over the interior
expected to diminish between 22z and 02z, which just a chance for any
MVFR cigs persisting overnight. Along the coast generally VFR
conditions expected to continue tonight through 18z Tue morning as
well, but occasional MVFR cigs remain likely through Tue morning.

KPDX AND APPROACHES...Primarily VFR tonight through 18z Tue morning.
Areas of MVFR cigs associated with light rain through 02z this
evening, then there remains a lesser chance for temporary MVFR cigs


.MARINE...970 mb low was near 46n 132w early Mon afternoon. Low is
expected to move slowly north tonight and Tue, beginning to weaken
late tonight. Gales over the waters, strongest over the outer
waters, will continue into Tue morning with the winds diminishing in
the afternoon. Wind waves and a fresh swell were in the process of
building today, with seas expected to peak tonight, ranging from
around 20 ft near the coast to 25 ft over the outer waters.

Another low, a bit weaker, is expected to move north off the OR and
WA coast near 130w Tue night into Wed night. Gale force winds will
be possible with this system, most likely Wed over the outer waters.


PZ...Gale Warning until noon PDT Tuesday for Coastal Waters from
     Cape Shoalwater WA to Florence OR out 60 nm.

     Small Craft Advisory for Rough Columbia River Bar until 5 PM
     PDT Tuesday.



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