986
FXUS66 KPQR 221100
AFDPQR

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

.SYNOPSIS...Another round of rain and wind today. Rain showers and
mountain snow shower for the weekend into early next week.
Potentially a dry period later next week.

&&

.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 and a mix of generally low-end VFR
and high-end MVFR cigs with pockets of IFR/LIFR conditions
(25%-30% probability) across the airspace. This system will
strengthen winds and bring some low level wind shear, especially
in the central and southern Willamette Valley. Winds will
gradually become southerly, with gusts up to 45 kt along the coast
and up to 30 kt in the Willamette Valley. As the system exits the
region around 00Z Saturday, will see post-frontal showers and
predominately VFR conditions. Winds will also begin to weaken
around 03Z Saturday.

PDX APPROACHES...Mixture of low-end VFR and high-end MVFR
conditions along with rain as the system moves northward. Winds
strengthen and become more southerly between around 12Z-15Z Friday
,with gusts up to 25 kt. Winds weaken after 03Z Saturday. /42

&&

.MARINE...A strong low pressure system will bring rapidly
increasing winds and seas across all waters today. Expect
southerly Storm Force wind gusts up to 60 kt by mid Friday
morning. With the strong winds, seas will also build quickly to
19 to 23 ft with a dominant wave period of only 10 to 12 seconds.
This will result in very steep and hazardous. 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.
/42-TK

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...High Wind Warning from 10 AM this morning to 10 PM PST this
     evening for ORZ101>103.

     Wind Advisory from 8 AM this morning to 7 PM PST this evening
     for ORZ114>117.

WA...High Wind Warning from 10 AM this morning to 10 PM PST this
     evening for WAZ201.

PZ...Gale Warning until 4 AM PST early this morning 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.

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

     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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