Small Craft Advisory 182, NWS Portland, OR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
825 PM PDT Tue Nov 2 2021

Updated Aviation, Marine and Beach Hazards

.SYNOPSIS...Light rain will taper off from south to north this
evening, with dry and seasonably warm conditions expected
through most of Wednesday. Another strong Pacific storm system
will bring rain and gusty southerly winds to much of the area
Wednesday night into Thursday. An active weather pattern then
looks to continue through early next week.

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.SHORT TERM...THROUGH FRIDAY...Light warm frontal rain is moving
across the area from south to north this afternoon, with
locations on the south Washington coast recording around two
tenths of an inch so far today while most areas have seen no
more than a few hundredths. Light rain will linger into later this
evening north of Hwy 22 and then end relatively quickly after
midnight as the front clears the area. Could see patchy fog
again tonight in the Willamette Valley given moist antecedent
conditions, but extensive higher level cloud cover and some
component of easterly winds through the Gorge should preclude
more widespread fog development, particularly in the Portland
metro area. Wednesday will be somewhat of a transition day
between systems, with our area located in the warm sector behind
the departing front. Valley locations could get quite warm for
early November given an offshore pressure gradient, with
widespread temperatures in the 60s and perhaps a few locations
in the south valley pushing 70 on Wednesday afternoon.

The main event for the short term will come Wednesday night into
Thursday as an approximately 990 mb surface low develops over
the NE Pacific and tracks towards Vancouver Island, with a
strong cold front moving through our coastal waters Wednesday
night and then inland on Thursday. Wind still seems to be the
primary threat with this system, with little change in thinking
for the High Wind Watch along the coast. Gusts of 50-55 mph
still appear probable, with some potential for gusts exceeding
60 mph along the central OR Coast. Will continue to assess the
potential for a Wind Advisory in the Willamette Valley on
Thursday, with gusts for now looking most likely to max out
around 40 mph. Retained a slight chance of thunderstorms along
the coast and adjacent coastal waters Wednesday night. The
overall convective threat should be fairly limited as the timing
of the most favorable low level wind field and the best shallow
instability do not line up as well as with other recent
systems. Forecast rainfall amounts from Wednesday night to
early Friday morning appear to be in line with previous
thinking, with generally 1-2 inches in the Coast Range, 0.5-1
inch in the valley, and over an inch in the Cascades. This
should present fairly minimal hydro issues, with the exception
of possible impacts on some of the typically flashier rivers
such as the Grays or the Wilson near Tillamook. Finally snow
levels remain fairly high through Thursday night, generally
around 4500-5000 feet. This should keep most of the snow in the
cascades above pass levels and limit any winter weather concerns
at least for the next few days. /CB

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.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...The extended
forecast will continue to see an active weather pattern with a
series of fronts bringing high chances for precipitation through
Tuesday. The 00Z WPC cluster analysis gives high confidence
that an upper level trough will build over the NE Pacific Friday
and push inland by Monday. Looking at the deterministic ECMWF,
a broad upper level trough will build in the Gulf of Alaska
swinging weak vortices around its base. Expect rain and lowering
overnight temperatures into the mid 40s Friday through Sunday.
Snow levels are expected to drop Friday night into Saturday
around 3500 ft. Models begin to diverge after Sunday on where
and when fronts will make landfall but all agree that the wet
weather will continue into early next week. -BKM

&&

.AVIATION...Generally VFR with lingering spots of MVFR/IFR
conditions within the Willamette Valley. Clouds should thin
overnight and may see LIFR conditions develop for south of KUAO
tonight into Wed morning provided winds are light enough. HREF
guidance indicating only 30-50% chance of LIFR in the above
mentioned area, so not a high confidence forecast. North of KUAO
will have offshore wind from the Columbia River Gorge. Given that
this is a gap driven wind, expect the gusts to be confined to
areas near the Columbia River. Easterly wind gusts at KTTD
expected to be around 25 kt through 06Z Wednesday with weaker
winds to the west. Rain and wind increase at the coast with MVFR
becoming likely after 18Z Wednesday and spread inland through
Wednesday afternoon. Slight chance of thunderstorms along the
coast staring 06Z Thursday.

For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse

KPDX AND APPROACHES...VFR expected to prevail next 24 hours,
possibility of patchy IFR along western approaches after 10Z
Wednesday. East winds gusting 25 kt at KTTD expected through 06Z
Wednesday. Expect gusty east winds at KPDX, however will likely
be sporadic. /42

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.MARINE...An active weather is expected to continue through
early next week as a series of Pacific systems affects the
region. A low near the north end of Vancouver Island will weaken
through Wednesday, but will be quickly replaced by another low
tracking northward near 130-133W by late Wednesday/early
Thursday. This system is expected to bring southerly Gales to
the outer waters late Wednesday afternoon, then impacting the
inner waters by early Thursday morning. Current guidance shows
the potential for a coastal jet early Thursday morning which
could result in southerly gusts of 40 to 45 kt as the associated
front moves into the waters. The front is expected to move ashore
around midday, with a good chance for Gale force westerly winds
behind the front.

.BEACH HAZARDS...Although conditions are still not expected to meet
high surf criteria, there will still be a rough surf on Thursday
with hazardous conditions for beachgoers. In fact, a Coastal Flood
Advisory for tidal overflow has been issued for the south Washington
coast and the north Oregon coast for Thursday afternoon when a
higher than normal tide will result in minor flooding up to one foot
above ground level in the the low lying areas near bays, sloughs,
and the lower reaches of the coastal rivers. In northwest Oregon
similar conditions in the past have resulted in minor flooding on
Highway 101 near Seaside, Nehalem, and/or Tillamook. Water has
covered parts of Frazier Rd, Miami Foley Rd at milepost 1, and the
intersection near Alderbrook and Possetti road. There has also been
flooding in the town of Rockaway Beach. In southwest Washington
similar conditions in the past have resulted in minor flooding in
Raymond, on Highway 101 near South Bend, and/or minor erosion on
Highway 105 near North Cove. -TK

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.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Coastal Flood Advisory from 10 AM to 4 PM PDT Thursday for
     North Oregon Coast.

     High Wind Watch from late Wednesday night through Thursday
     afternoon for Central Oregon Coast-North Oregon Coast.

WA...Coastal Flood Advisory from 10 AM to 4 PM PDT Thursday for
     South Washington Coast.

     High Wind Watch from late Wednesday night through Thursday
     afternoon for South Washington Coast.

PZ...Gale Watch from Wednesday afternoon through Thursday afternoon
     for coastal waters from Cape Shoalwater WA to Florence OR
     out 60 nm.

     Gale Warning until 3 AM PDT Wednesday for Waters from Cape
     Shoalwater WA to Cascade Head OR from 10 to 60 nm.

     Small Craft Advisory until 5 PM PDT Wednesday for Waters from
     Cascade Head to Florence OR from 10 to 60 nm.

     Small Craft Advisory from 3 PM to 7 PM PDT Wednesday for
     Columbia River Bar.

     Small Craft Advisory until 3 AM PDT Wednesday for Coastal
     waters from Cape Shoalwater WA to Cascade Head OR out 10
     nm.

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