NWS Portland, OR wrote its last area forecast discussion before the first event at Oct 13, 2:06 PM PST, 9 minutes earlier.
Area forecast discussion, Oct 13, 2:06 PM PST, 9 minutes before
Area Forecast Discussion
National Weather Service Portland Oregon
306 PM PDT Thu Oct 13 2016
.SYNOPSIS...When it rains, it pours. And it is. Rain continues. Winds
will increase this afternoon, then ease back later tonight. Remains
wet and somewhat breezy on Friday, Then the strongest storm yet, the
Ides of October Storm, will push into the region Saturday. This will
likely bring potentially strong damaging winds and another round of
heavy rain to much of the region. Unsettled weather continues into
early next week.
&&
.SHORT TERM...(Tonight through Sunday)...Lot of rain across the
region today. Generally, have seen 1 to 3 inches of rain since
midnight over the coastal mountains, and even a few spots. And it is
still raining. Likely to see those rainfall double for the final
numbers for today. Been enough to trigger big jumps on many rivers,
especially those draining the Willapa and Coast Ranges. Though most
of the flooding seems to be more low-lying areas and poor drainage
type, do have a lone river flood warning this afternoon. That is on
the Grays River in Wahkiakum County, river should push just above
flood stag this evening, with minor flooding expected.
Elsewhere, decent wave now pushing up the Oregon Coast, with winds
now increasing along the south Oregon Coast where winds are now
gusting 45 to 55 mph. at 230 pm, Sea Lion Caves now gusting 60 to 65
mph. Winds will continue to pickup across the region through 5 pm,
with first to increase over Lane County and spreading north to the
Columbia River by 6 pm. Current High Wind Warnings/Winds Advisories
remain on track. Winds will ease back later this evening.
Models show a weaker system moving through on Friday, mostly as the
bent-back occlusion from the low off the Washington coast shifts
across western Washington. But with the bent-back occlusion shifting
inland on Fri am, winds will remain somewhat elevated along the south
WA/north Oregon and nearby coastal mountains Fri am with gusts 40 to
50 mph. Elsewhere, will remain somewhat breezy, albeit not too out of
the ordinary. Should see plenty of showers. As the bent-back shifts
inland late tonight and Fri, will see bit of cooler more unstable air
shift inland. As a result, will keep slight chance of thunderstorms
along the coast and possibly into the Coast Mtns late tonight into
Fri am.
The next significant storm, now referred as the Ides of October
storm, incorporates the remains of Typhoon Songda, which is currently
around 42N, 175E. As the remains of this typhoon enter the 180-200
kt Jet Stream over the Central Pacific, it will get entrained into
the storm track and become the system which will impact the Pacific
Northwest on Saturday. Compute models now showing better agreement
in resolving the storm and its storm track. Some differences still in
the models, but seems now have better confidence for the storm. 12Z
GFS more aligned with the 12Z ECMWF, with 12Z NAM splitting the
difference. Either way, all show rather deep low coming up from the
southwest and tracking offshore as it moves to near Cape Flattery by
late Saturday evening. Will see strong winds increasing on West
Central Oregon coast by early afternoon, then spread north and
inland through rest of the afternoon/evening. This storm has
potential to create damaging winds across a wide area of the region.
So, have issued a High Wind Watch for all of the region for Saturday
afternoon and evening. Again, winds could wind up being a bit
stronger or weaker, as all depends on the storm track distance from
shore. Closer to shore, stronger the winds.
Will see more rain tonight through Saturday night, with perhaps as
much as 3 to 6 inches coastal mountains, and generally 2 to 4 inches
for the coast and Cascades. Should see 1 to 3 inches in the valleys.
At this point, there appear to be enough breaks in between the
systems to prevent river flooding. But with leaves falling off trees
now, expect areas of low-lying and other poor drainage areas, and
some urban flooding that could be exacerbated by leaf-clogged storm
drains. Rockey.
.LONG TERM...(Sunday night through Thursday)...Broad upper trough
will remain over the Pacific Northwest coast Sunday night and Monday
morning with an associated front likely moving through Monday
morning. After that models begin to diverge some with timing of lows
moving toward the coast. This is due the the difficulty the
models having in picking up on tropical moisture from the western
Pacific being injected into the westerlies. GFS has been consistently
showing a 1000mb low moving onto the Washington coast Tuesday with
the ECMWF having a much slower solution bringing this system over a
developing weak ridge on Tuesday night with rain brushing Northwest
Oregon. Both the ECMWF and GFS build the ridge Wednesday and
Thursday pushing the storm track mostly into Washington. I have
lowered the chance of precipitation some for Wednesday night and
Thursday, but will still leave a chance or slight chance of rain in
the forecast due to the uncertainty in the models. Schneider
&&
.AVIATION...A rapidly strengthening low pressure system will pass
from south to north just offshore later this afternoon and this
evening. This will result in continued moderate to heavy rain in
addition to increasingly gusty southerly winds. Expect the coast
to see the most significant wind impacts, with gusts of 45 to 50
kt possible from around 23Z through 04Z. Winds will also pick up
over the interior, with gusts of 25 to 35 kt during the same time
period. Flight conditions are currently mainly MVFR with pockets
of IFR, but expect more periods of VFR conditions to develop over
the next several hours as the winds pick up. A cold front will
move through the region from 03Z to 06Z Fri. Rain will to taper to
showers behind the front overnight through Fri morning. Expect
conditions to become predominantly VFR, with periods of MVFR
during heavier showers. There will also be a slight chance of a
thunderstorm for the coastal TAF sites overnight or Fri morning.
Gusty winds will decrease somewhat overnight, but will remain
fairly breezy into Fri morning.
KPDX AND APPROACHES...Mainly MVFR conditions currently, but
expect periods of VFR to develop later this afternoon and this
evening. However, southeast winds will become gusty by around 23Z,
with gusts 25 to 35 kt possible through the evening. A cold front
will move through between 03Z-06Z Fri, after which winds will
shift from SE to SSW. Winds subside somewhat overnight. Expect
primarily VFR overnight into Fri morning with occasional MVFR
conditions in heavier showers. Pyle
&&
.MARINE...A developing low pres system will move through the
offshore waters later this afternoon and this evening. The low is
modeled to reach around 980 mb by the time it is west of the
Washington coast. Expect southerly winds to increase rapidly from
south to north later this afternoon. The current Storm Warning
still looks good, with gusts 50 to 55 kt expected. There may be
isolated gusts to 60 kt. Seas will also build quickly in response
to the winds, likely peaking around 22 to 25 ft late this evening.
Seas will be wind wave dominated, with most of the wave energy
short period and out of the south. However, given that this is the
first major system of the season, a high surf advisory has been
issued.
Winds will begin to subside after midnight as the low moves off to
the north. The fcst models indicate another surface trough will
follow on Fri morning, which should keep winds up above gale
force through midday Fri. Then there will be a lull later Fri into
early Sat between systems. Seas should drop below 20 ft during
this time, but may remain up around 15 to 18 ft.
A considerably stronger low pres system is then on tap for Sat.
The fcst models have come into much better agreement today with
the 12Z cycle of runs. The general consensus is now for a low to
develop around 40N, strengthening rapidly as it turns sharply
north inside of 130W. The models currently have the low bottoming
out somewhere around 970mb, then moving onshore somewhere along
the Washington coast or southern Vancouver Island. The track of
the low is a little further south and east from the previous fcst
track, and the strength of the low a bit weaker. This new solution
results in higher winds and slightly lower waves than previously
fcst. Have adjusted accordingly this afternoon. Winds increase
rapidly late Sat morning into Sat afternoon and continue into the
evening hours. Expect winds will reach as high as 40 to 50 kt,
with gusts 60 to 65 kt. Decided to issue a hurricane force wind
watch with the afternoon fcst package. Have backed off the waves
from the mid 30s we previously had, now showing a peak of 28-32
ft late Saturday. We will almost certainly need a High Surf
Warning for Sat. There are also concerns about coastal flooding,
as we are entering a high tidal cycle. However, the highest seas
and surge currently appear to fortuitously occur during a low
tide, so we may escape the most serious impacts.
Considerably lighter westerly winds should spread into the waters
Sunday and Monday, which will likely allow seas to subside well
into the teens during this period. However, there is a chance a
third surface low pressure system could bring another round of
gale to storm force winds late Monday night or Tuesday. Pyle
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 10 PM PDT this evening for Central
Willamette Valley-Greater Portland Metro Area-South
Willamette Valley.
High Wind Warning until midnight PDT tonight for Central Coast
Range of Western Oregon-Central Oregon Coast-Coast Range
of Northwest Oregon-North Oregon Coast.
High Surf Advisory until 3 AM PDT Friday for Central Oregon
Coast-North Oregon Coast.
High Wind Watch for all of northwest Oregon for Saturday
afternoon and evening...except for Columbia Gorge.
WA...Wind Advisory until 10 PM PDT this evening for Greater
Vancouver Area.
High Wind Warning until midnight PDT tonight for South
Washington Coast-Willapa Hills.
High Surf Advisory until 3 AM PDT Friday for South Washington
Coast.
High Wind Watch for all of southwest Washington for Saturday
afternoon and evening.
PZ...Storm Warning until 2 AM PDT Friday for Coastal Waters from
Cape Shoalwater WA to Florence OR out 60 nm.
Hurricane Force Wind Watch from Saturday morning through
Saturday evening 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 Friday.
&&
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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.