FXUS66 KPQR 220553
AFDPQR
Area Forecast Discussion...UPDATED
National Weather Service Portland OR
953 PM PST Thu Nov 21 2024
...Updated aviation discussion...
.SYNOPSIS...A few showers today, then rain returns tonight into
Friday along with another round of windy conditions Friday. Showery
weather followers over the weekend into next week.
&&
.DISCUSSION...Today through Wednesday...A low continues to drift
northeast-ward towards the PNW, and weak showers continue to drift
through the area for the rest of today. This low continues to deepen
as it moves closer. This system supported by a 125-130kt jet will
rapidly deepen tonight as it swings to just inside 130W of the WA
coast late Friday afternoon. Pressure drop with this storm will not
be as impressive as the recent meteorological bomb with about 18 mb
drop in 24 hours. This system will bring another round of strong
winds over the coastal waters and at the coast. Winds are currently
generally easterly, with some gusts up to 20-25mph through the
Columbia River Gorge; these will shift southerly by 8pm Thu as the
system approaches, and gusts will increase around then. Looking at
the latest high-resolution HREF guidance, between this evening and
Friday morning, 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 (80% confidence). As a
result, a High Wind Warning has been issued at the coast, while a
Wind Advisory has been issued for the central Willamette Valley.
Rain will spread south to north tonight into Friday morning, with IVT
plume peaking around 500 kg/ms. Duration will be relatively short, as
the main stream of moisture only briefly crosses into the area as the
warm front sweeps north with the low. Inland, 24h total QPF looks to
be around 0.5-1.0" from 4 PM Thursday through 4 PM Friday. Over the
mountains and coast, QPF looks closer to 1.25-2" during this time.
Hydro impacts continue to look minimal, with HEFS guidance showing
less than 5% chance of minor flooding for Coast Range rivers.
Snow levels continue to rise above Cascades pass level ahead of the
incoming system to around 7000-8000 feet tonight, so will have
another round of rain on snow to impact the snow pack. Snow levels
tumble Friday afternoon once the cold air wrapping around the low
pushes into the region. Snow levels drop to around 4500 ft Friday
afternoon, then 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 Sun day afternoon (48 hours), and closer to 1 ft for the
volcano peaks.
More benign conditions over the weekend into mid next week an upper
trough lingers over the northeast Pacific and Pacific northwest. This
will bring showers at times. Also there is a chance for thunderstorms
over the coastal waters and coast for the weekend. /mh/JLiu
&&
.AVIATION...A low pressure system moving into the area from the
south will bring light rain and a mix of low-end VFR and high-end
MVFR cigs tonight. Guidance suggests a 50-80% chance of MVFR cigs or
lower along the coast and Willamette Valley between 06-15z Fri.
This system will strengthen winds and bring some low level wind
shear, especially in the central and southern Willamette Valley.
Winds shift gradually shift southerly Friday, with gusts up to 35-40
kt along the coast and 25-30 kt in the Willamette Valley.
As the system exits the region after 18z Fri, will see post- frontal
showers and predominately VFR thresholds. Winds will also begin to
weaken Friday afternoon.
PDX APPROACHES...Mix of low-end VFR and high-end MVFR cigs tonight
with rain as the system moves through. Will see winds strengthen and
turn more southerly between 12-18z Fri, with gusts up to 20-25 kt.
Winds weaken after 00z Sat as the system exits. -Alviz
&&
.MARINE...A strong low pressure system will bring rapidly
increasing winds and seas to the waters Thursday night into Friday
morning. Expect gale force winds to develop Thursday night before
quickly ramping up to storm force winds with gusts up to 55 kt by
mid Friday morning. Although winds will be east to southeast
Thursday night, expect winds to veer to the south Friday morning
as the aforementioned low moves northward. With the strong winds,
seas will also build quickly to 20-23 ft. Given a dominant wave
period of only 10 seconds, seas will be very steep and hazardous
through the day. However, seas will begin rapidly falling Friday
night to around 15 ft before falling to 10 to 12 ft by late
Saturday morning. This will be in response to the decreasing winds
during that time as gusts fall to around 25 kt or lower Saturday
morning. This subsiding trend is expected to continue through the
weekend into early next week. In fact, the forecast calls for seas
under 10 ft by Monday with winds around 15-20 kt or less. -TK
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning from 10 AM to 10 PM PST Friday for ORZ101>103.
Wind Advisory from 8 AM to 7 PM PST Friday for ORZ114>117.
WA...High Wind Warning from 10 AM to 10 PM PST Friday for WAZ201.
PZ...Gale Warning from 10 PM this evening to 4 AM PST Friday for
PZZ210-251>253-271>273.
Storm Warning from 4 AM to 7 PM PST Friday for PZZ210-251>253-
271>273.
&&
$$
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