Hillsboro, Oregon 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

914
FXUS66 KPQR 210554
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
953 PM PST Wed Nov 20 2024

Updated aviation discussion...

.SYNOPSIS...Showers continue into Thursday. Another
weather system may bring another round of wind impacts as well
as widespread rain late Thursday into Friday, but forecast
confidence remains low at this time. Showery weather continues
through the weekend, with lighter snow accumulations expected.

&&

.DISCUSSION...Wednesday through Tuesday...Currently in a showery
post-frontal regime, with the offshore low slowly moving northward
towards Alaska. Winds have decreased slightly, with gusts up to 25
mph inland and 30-35 mph at the coast; these continue to decrease,
becoming non-impactful by Wednesday evening-time. Snow levels are
currently around 4000-4500, and additional accumulations remain
possible at the Cascades passes from any remaining showers. A Winter
Weather Advisory for the Oregon Cascades over 4500 ft through 4am
Thursday has thus been reissued; snow amounts will be 3-6 inches
between now and then, but travel likely will continue to be difficult
as temperatures drop overnight.

Thursday looks fairly innocuous, with weak passing showers at times.
Snow levels rise to 5000 ft, ending threat of any impactful
accumulations at the Cascades passes. Late Thursday night going into
Friday morning, the next low system rides up the western coast from
California. Winds shift southerly, and Friday can expect to see some
slightly stronger gusts. Max wind gusts on Friday see right around a
50% chance of reaching 35 mph or greater in the Willamette Valley,
and a 60% chance of reaching 50 mph at the coast.

Thursday night and Friday will see stratiform rain returning to the
area, with an IVT plume peaking around 500 kg/ms. Duration will be
relatively short, as the main stream of moisture only briefly crosses
into the area before moving back further southwest of our area.
Inland, total QPF looks to be around 0.5-1.0" from 4PM Thursday
through 10AM Friday. Over the mountains and coast, QPF looks closer
to 1.25-1.75" during this time. Hydro impacts continue to look
minimal, with HEFS guidance showing around 5% chance of minor
flooding for most Coast Range rivers. Past that, we remain generally
cool and unsettled, with low rain accumulations and little confidence
in exact timing of specific systems. /JLiu

&&

.AVIATION...Predominately VFR thresholds tonight with some
occasional MVFR cigs possible. Guidance suggests a 20-30% chance for
MVFR cigs through 18z Thu. Will note that there is a 15-20% chance
for thunderstorms along the coast through 12z Thu. Any thunderstorms
that do form may bring gusty winds, small hail, and brief downpours
which can lead to vis reduction.

Tomorrow (Thursday), another wave of low pressure will approach from
the SW, increasing rain chances from south to north. This
approaching system will also turn winds more east/northeast tomorrow
afternoon. Not looking too gusty, except for the far east Portland
Metro (KTTD) where Gorge winds in the afternoon could gust up to 25
kt. Otherwise, still looking at predominately VFR cigs through the
end of the TAF period.

PDX APPROACHES...Predominately VFR thresholds through the TAF period
with a 10-30% chance of MVFR cigs. Easterly winds continue,
generally around 10 kt or less.   -Alviz


&&

.MARINE...Thunderstorms will continue through Thursday morning for
a threat of lightning, small hail, and erratic winds. Radar
imagery has shown rotation with some of the showers this
afternoon indicating that waterspouts are possible as well.

The marine winds are expected to lower below gales in the next
few hours. The seas have been slow to subside with buoys reporting
seas around 25 feet. With wind waves being a large contributer to
the large seas, they will lower late tonight as the winds ease.
Expect seas to lower below 20 feet by midnight tonight.

The next low is expected to increase winds and seas Thursday night
and Friday night. Forecast confidence is high that there will be
at least gale force winds with this next system. NBM model
forecasts a 50-75 percent chance of greater than 48 kt wind
gusts, and have issued a Storm Watch. Seas are expected to build
above 20 ft Friday morning, mostly due to wind driven seas.

&&

.BEACH HAZARDS...Made no change to the High Surf Advisory as buoy
observations still support high enough energy from the current
west marine swell to produce hazardous surf conditions through
this evening. 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
shoreline.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Weather Advisory until 4 AM PST Thursday for ORZ126>128.

WA...None.

PZ...Hazardous Seas Warning until 10 AM PST Thursday for PZZ210-
     251>253-271>273.

     Storm Watch from late Thursday night through late Friday night
      for PZZ210-251>253-271>273.
&&

$$

www.weather.gov/portland

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