334
FXUS66 KPQR 221756 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
956 AM PST Fri Nov 22 2024

Updated aviation and marine discussions.

.SYNOPSIS...Another round of rain showers and wind today, windiest at
the coast. Rain showers and mountain snow showers over the weekend
into early next week. Trending towards drier weather later next week
with seasonable temperatures.

&&

.DISCUSSION...Today through Thursday...990 mb surface low near 44N
130W as of 1 AM.  Warm front now approaching the central Oregon coast
with near gale force southeast winds developing.  Winds should shift
to the south early this morning and increase. This should open up the
pressure gradient to allow strong winds to reach the coastline where
a High Wind Warning is in effect for the beaches and headlands today
for gusts up to 60 mph. Winds will increase inland as well with
gusts 30 to 45 mph inland of the coast. Current Wind Advisory for
the central Willamette Valley looks good for gusts to 45 mph.
Appears winds won`t be quite as strong for the south and north
Willamette Valley into southwest WA interior.  The Wind Advisory
goes through 7 pm but current indications show may end a few hours
earlier. Main impacts from wind are broken tree branches and perhaps
some trees in soggy ground become uprooted - potentially resulting
in power outages and other damage.

Looking at the latest high-resolution HREF guidance, southerly winds
at the coast could potentially gust up to 60 mph (60-80% confidence)
at the beaches and headlands, and up to 40-45 mph in the central
Willamette Valley (50-80% confidence) with 20-50% confidence
elsewhere in the interior lowlands.

Rain will change to showers late this morning and rain rates ease.
In the past 12 hours ending at 2 am - rain amounts were generally
under 0.5 inches, but 0.7 to 1 inch for the central coast/coast
range (rain started earlier there.)  Forecast 24h total QPF ending
10 PM tonight looks to be around 0.8 to 1" for the interior valleys,
1-2" over the mountains and coast. Hydro impacts continue to look
minimal, with HEFS guidance showing less than 5% chance of minor
flooding for Coast Range rivers.

There will be a slight chance for thunderstorms over the coastal
waters and inland up to the coast range later today into Sunday.
Can`t rule out another round of waterspouts during this time, as most
ingredients for development are present.

Snow levels around 7000-8000 feet this morning drops to near Cascade
pass level this evening as the colder air wraps around the backside
of the long into the region.  Snow levels drop to around 3000-3500 ft
Saturday and Sunday. Snow amounts during this time look to be around
1/2 foot at passes Friday night to Sunday afternoon (48 hours), and
closer to 1 ft for the volcano peaks. At this time no winter
headlines are expected.

An upper low remains off the PacNW coast through the weekend. Models
show another shortwave rotating around the low (much weaker than
recent storms) and brings a front near or partially over the western
OR and WA. Detail differ between deterministic models, though
at NBM mean 24-hr QPF ending 4 pm Sun shows about 1-1.5 inches over
the coast/coastal mountains; and about 0.5 inches the interior
lowlands. This should not pose significant hydro issues.

More benign conditions by mid next week the upper low shifts inland
and weakens for decreasing showers. Potentially a dry period for the
latter half of next week as an upper level ridge starts to develop
offshore.

&&

.AVIATION...A low pressure system moving into the area from the
south will bring light rain showers and a mix of generally low-
end VFR and high-end MVFR cigs, except at KHIO where low-end MVFR
cigs are expected to continue through 22-23z Friday. Low-level
wind shear concerns diminish after 19-20z Friday. Winds will
gradually become southerly, with gusts up to 40-45 kt along the
immediate coast and up to 25-30 kt in the Willamette Valley,
strongest in the central Willamette Valley near KSLE. As the
system exits the region around 00Z Saturday, will see post-frontal
showers spread from south to north and predominately VFR
conditions. Winds will also begin to weaken between 00-03z
Saturday.

PDX APPROACHES...Mixture of low-end VFR and high-end MVFR
conditions with a few light rain showers nearby through Friday
morning. VFR conditions expected Friday afternoon through Friday
night with a period of breezy southeast winds between 19z Friday
and 01z Saturday with gusts up to 25 kt. Winds weaken thereafter
while veering to the south.  -TK

&&

.MARINE...A strong low pressure system will bring rapidly
increasing winds and seas across all waters today. Expect
southerly Storm Force wind gusts as high as 50-55 kt by late
Friday morning. With the strong winds, seas will also build
quickly to 18 to 22 ft with a dominant wave period of only 10 to
12 seconds. This will result in very steep and hazardous seas.
However, conditions will begin to rapidly subside tonight/Saturday
morning. Expect seas 13 to 15 ft late tonight before falling to
10 to 12 ft by late Saturday morning. Winds will also decrease
during that time as gusts fall to around 25 kt or lower Saturday
morning. This overall trend is expected to continue through the
weekend and into the start of the upcoming week. In fact, the
forecast calls for seas under 10 ft by Monday with wind gusts
below 20 kt.  -TK

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...High Wind Warning until 10 PM PST this evening for ORZ101>103.

     Wind Advisory until 7 PM PST this evening for ORZ114>117.

WA...High Wind Warning until 10 PM PST this evening for WAZ201.

PZ...Storm Warning until 4 PM PST this afternoon for PZZ210-251>253-
     271>273.

     Gale Warning from 4 PM this afternoon to 10 PM PST this evening
     for PZZ210-251-252-271-272.

     Hazardous Seas Warning from 10 PM this evening to 4 AM PST
     Saturday for PZZ210-251-252-271-272.

     Hazardous Seas Warning from 4 PM this afternoon to 4 AM PST
     Saturday for PZZ253-273.
&&

$$

www.weather.gov/portland

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