NWS Portland, OR wrote its last area forecast discussion before the first event at Feb 24, 11:01 AM PST, 2 hours 14 minutes earlier.
Area forecast discussion, Feb 24, 11:01 AM PST, 2 hours 14 minutes before
Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1101 AM PST Mon Feb 24 2025
.SYNOPSIS...One more round of moderate to heavy rain and strong
winds today through early Tuesday as the last in a series of
strong frontal systems impacts northwest Oregon and southwest
Washington. Lowering snow levels will also bring accumulating
snow back to the High Cascades beginning this afternoon. Much
quieter weather is in store from Wednesday onward.
&&
.SHORT TERM...Now through Tuesday Night...Water vapor imagery
reveals a rapidly developing area of low pressure approximately
300 miles off the south Oregon Coast as of 11 AM Monday as the
last in a series of strong frontal systems takes aim on our area
today. The initial warm front has nearly exited the area with a
cold front quickly on it's heels. Numerous showers will
continue in the post frontal environment into early Tuesday.
Thus far, thunderstorms have already formed over the marine
waters, but some heavier showers are moving over the Coast
Range. These showers have the potential to produce lightning as
well. Model QPF amounts from today until showers start to taper
off late Tuesday morning range from 1.00-1.50 inches for the
coast, 2-3" with locally higher amounts for the Coast Range and
Willapa Hills, 0.50-1.00" for the interior lowlands, and 1-2
inches for the Cascades. Refer to the Hydrology section below
for the latest details regarding remaining flood concerns for
this event.
Still expect strong south winds to develop across the area today
as the the surface low offshore quickly deepens to the upper 970
mb range by late this morning and races northeastward towards
the Juan de Fuca Strait this evening. A High Wind Warning
remains in effect for coastal areas and the adjacent higher
terrain from this morning through early Tuesday morning, with
a Wind Advisory for the interior lowlands in effect at noon
today through early Tuesday morning. Expect gusts as high as 60
mph for coastal areas including the inland coastal communities,
while winds could gust as high as 70 mph on beaches and
headlands and the higher points of the Coast Range and Willapa
Hills. Meanwhile, expect gusts to 45 mph from the Willamette
Valley up through the Cowlitz Valley of southwest Washington.
Winds will peak early this evening into the overnight hours as
winds shift more southwesterly, with hi-res guidance showing
probabilities above 60% for winds to gust as high as 50 mph from
Salem north into the Portland/Vancouver metro this evening.
Recent high resolution models suggest around a 20% chance of
gusts up to 60 mph in the central Willamette Valley and in the
southern Portland-Metro. Confidence is low at this point as it
will greatly depend on where the low pressure system ends up. If
it shifts to the north and a little closer to the shore, then
interior winds will be stronger. Strongest winds will diminish
by early Tuesday morning as the surface low to the north quickly
weakens, but breezy conditions will persist through late
Tuesday morning.
The final piece of the forecast puzzle will be winter weather
concerns in the Cascades as snow levels drop to 3500-4000
behind the departing cold front later this afternoon. The
heaviest snowfall will remain focused on the south Washington
Cascades as strong, deep-layer southwest flow supports
impressive orographic enhancement of QPF values. Expect 1-2 feet
of snow above 4000 feet from late this afternoon through
Tuesday afternoon. While not quite as impressive, QPF values
have also crept upward farther south in the Oregon Cascades.
Have issued a Winter Weather Advisory for the Lane, Linn, and
Marion Cascades as a result, with snow amounts expected to
exceed six inches through Santiam and Willamette Pass this
afternoon through Tuesday afternoon. Did not issue any
headlines for the north Oregon Cascades as snow accumulations
should be more modest around Government Camp and Hwy 26, with
heavier accumulations confined to Mount Hood and the ski areas.
Conditions improve Tuesday afternoon through Tuesday night as
winds diminish and shower activity quickly tapers off behind
the departing trough and high pressure begins to build over the
area. -Muessle/CB
.LONG TERM...Wednesday through Sunday...Ensembles continue to
favor upper level ridging across the western CONUS during the
latter half of the week, yielding quieter weather conditions
across the area going forward. A weak shortwave trough moving
over the top of the ridge keeps at least a chance of
precipitation in the forecast on Thursday, but amounts would
remain very light and the vast majority of individual ECENS
and GEFS solutions keep at least the inland parts of the area
completely dry Wednesday through Friday. In all, expect pleasant
conditions by late February standards, characterized by
seasonably mild temperatures in the upper 50s to low 60s across
the area. Medium range guidance continues to hint at a
troughier and thus wetter solution returning sometime next
weekend, the details of which remain sparse at this time. /CB
&&
.AVIATION...The region is still on track to see a strong low
pressure system bring rain, heavier showers, and increasing winds
this afternoon through tonight. The earlier warm-frontal boundary
has lifted northward with a cold-front now racing into western
Oregon and SW Washington. After this band of precipitation passes
through conditions should trend toward widespread VFR after 20-22z,
although this is also when post-frontal showers will be
developing across the area. Expect brief periods of MVFR cigs and
visby reductions under these aforementioned showers. Keep in mind
stronger showers and thunderstorms (15-20% chance all sites) will
have the potential to produce heavy rain and gusty outflow wind
gusts up to 40-45 kt.
In addition to occasional outflow wind gusts near convection,
background winds will be on the increase as well. Expect
widespread wind gusts ranging between 30-50 kt from this
afternoon/evening into the overnight hours, strongest at the
coast and near KSLE. Lastly, low-level wind shear is expected late
this morning into the afternoon during the transition to these
stronger background winds - elevated winds near 2000 ft will peak
between 40-60 kt.
PDX AND APPROACHES...Expect mainly VFR cigs through the TAF period,
aside from brief periods of high-end MVFR cigs possible between
between 18-20z with a band of stratiform rain that will be
lifting over the terminal from the south. Behind this band of
rain, post-frontal rain showers and possible thunderstorms
(15% chance) are expected through this afternoon and evening.
Stronger showers and storms will have the potential to produce
heavy rain, reduced visibilities and gusty outflow wind gusts up
to 40-45 kt. East winds persist until 20-21z which will create
low level wind shear concerns as southerly winds near 2kft rapidly
increase. -Schuldt/DH
&&
.MARINE...A strong low pressure system continues to develop
off the coast of southern Oregon this morning. Southeast winds
will become more southerly as a warm front lifts across the
coastal waters this morning. The surface low is expected to deepen
to around 978 mb as it approaches 130W and 45N by mid-day. The
initial burst of gale to storm force winds, with gusts up to
40-50 kt, is expected later this morning into early afternoon. A
stronger push of southwesterly winds arrives later this afternoon
with gusts up to 60 kt, likely continuing through the overnight
hours. Winds will begin to ease by early Tuesday morning as the
surface low weakens and pushes inland near the Olympic Peninsula
of NW Washington. The Storm Warming remains in effect for all
coastal waters, including the Columbia River Bar, through 4 AM
Tuesday.
Seas around 10 to 12 ft this morning will gradually build today
in response to the strong winds. Seas during this time will be
very steep, choppy and hazardous. A dominant southwesterly swell
pushing into the coastal waters later today into early Tuesday
morning will result in combined seas building above 20 ft this
afternoon, and peaking around 30 to 35 ft overnight. Seas are not
forecast to fall below 20 ft until sometime Tuesday afternoon.
Seas eventually subside to around 8 to 10 ft by Wednesday morning.
Conditions continue to improve as onshore winds ease through
Tuesday and turn offshore by Wednesday morning. A weak front
approaches the waters late Wed into Thursday. -DH
&&
.BEACH HAZARDS...
The advisory has been upgraded to a High Surf
Warning along the coast from 4 PM Monday to 4 PM Tuesday as there
is high confidence for high surf conditions. Large waves and
hazardous surf conditions are expected due to an increasing
southwesterly swell, peaking around 30 ft and producing breakers
in the surf zone up to 34 ft. Destructive waves may wash over
beaches, jetties, and other structures unexpectedly. People can be
swept off rocks and jetties and drown while observing high surf.
Minor beach erosion may damage coastal properties and buildings.
Higher than normal water run-up is expected on beaches and low-
lying shorelines.
In addition, confidence has increased for minor tidal overflow
flooding around high tide Tuesday morning for isolated locations
along the south WA and north Oregon coast due to a combination of
elevated river levels coinciding with high tide and an incoming
tidal anomaly. Minor tidal overflow flooding, up to one foot
above ground level, is expected in the low lying areas near bays,
sloughs, and the lower reaches of the coastal rivers. Therefore, a
Coastal Flood Advisory has been issued from the south WA and
north OR coast from 8AM-2PM Tuesday.
&&
.HYDROLOGY...
The last in a series of strong frontal systems will
bring one more shot of moderate to heavy rain to the area
through early Tuesday, with the coast and Coast Range set to see
the highest QPF amounts. The areal Flood Watch was cancelled
early as rainfall rates today generally look to remain int he
one to two tenths per hour range across the area. This should
continue to minimize any widespread concerns for flooding due
to ponding of water or poor drainage. Likewise, rainfall rates
will remain well below thresholds for any debris flow issues on
recently burned areas. Landslide concerns will also diminish in
the High Cascades today as snow levels drop to 4000 feet by this
afternoon. This leaves individual river flooding as the
lingering hydro concern moving forward. Most coastal rivers
have trended down below action stage during the period of dry
weather overnight, and are forecast to remain there for the
duration of the event. The Siuslaw River at Mapleton is the lone
exception as it remains near minor flood stage early this
morning, but expect that river to also drop below action stage
by later this morning. Cancelled a Flood Warning for the
Clackamas River at Estacada as the river crested just below
minor flood stage overnight and is now trending back down. A
Flood Warning remains out for the Clackamas River near Oregon
City, but recent observational trends suggest the river will
also crest just below flood stage at this location later this
morning. Finally, several of the slower responding Willamette
tributaries will peak near or just above minor flood stage later
tonight or Tuesday. A Flood Watch remains in effect for the
Luckiamute River at Suver and the Pudding River at Aurora, with
several other slower responding rivers lingering in action stage
into Wednesday/Thursday. /CB
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Wind Warning until 4 AM PST Tuesday for ORZ101>103-106-
107.
High Surf Warning from 4 PM this afternoon to noon PST Tuesday
for ORZ101>103.
Coastal Flood Advisory from 8 AM to 2 PM PST Tuesday for
ORZ101.
Wind Advisory until 4 AM PST Tuesday for ORZ104-105-108>118.
Winter Weather Advisory from 4 PM this afternoon to 4 PM PST
Tuesday for ORZ127-128.
WA...High Wind Warning until 4 AM PST Tuesday for WAZ201-203.
High Surf Warning from 4 PM this afternoon to noon PST Tuesday
for WAZ201.
Coastal Flood Advisory from 8 AM to 2 PM PST Tuesday for
WAZ201.
Wind Advisory until 4 AM PST Tuesday for WAZ202-204>208.
Winter Storm Warning from 4 PM this afternoon to 4 PM PST
Tuesday for WAZ211.
PZ...Storm Warning until 4 AM PST Tuesday for PZZ210-251>253-
271>273.
&&
www.weather.gov/portland
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