232
FXUS66 KPQR 040448 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
948 PM PDT Mon Jun 3 2024

Updated aviation discussion...

.SYNOPSIS...Another disturbance will bring rain to much of SW
Washington and portions of NW Oregon tonight into Tuesday, with
lighter shower activity continuing elsewhere. Temperatures
begin a steady upward trend on Wednesday, peaking with high in
the upper 80s to low 90s in the interior lowlands Friday and
Saturday.

&&

.DISCUSSION...Radar imagery shows scattered shower activity
ongoing across northwest Oregon and southwest Washington this
afternoon in moist onshore flow as one system departs into the
northern Rockies and another approaches from the eastern
Pacific. This next system is currently centered approximately
600 miles off the BC coast, with a 150 kt jet streak at the
base of the upper level trough taking aim on Vancouver Island
and the Washington coast. At the surface, a frontal system
arcing southeastward towards the Washington and Oregon coastal
waters will approach the area tonight into Tuesday morning and
bring the next round of steadier precipitation. As most of the
energy from this next system will be focused north of the area,
there will be a fairly sharp gradient of precipitation across
the area, with heavier rain focused over southwest WA and far
northwest OR and lighter shower activity persisting south of a
roughly Tillamook-Portland-Mt Hood line. In terms of QPF,
guidance is in line with previous forecast cycles, depicting
another 0.25-0.50" of rain through tomorrow morning from
northern coastal areas to the Willapa Hills and south WA/north
OR Cascades, with lesser amounts of a tenth or two for lowland
locations including Portland. However, some of the exposed west
slopes of the Coast Range and Cascades could pick up another
1.00-1.25" where orographic support is maximized. Meanwhile,
locations farther south from Salem to Eugene will likely be
limited to less than a tenth of an inch through Tuesday. Shower
activity will then gradually wind down across the area Tuesday
night into Wednesday morning as the system departs to the east.

The shift back to a warmer and drier pattern will commence on
Wednesday as a ridge of high pressure begins to build east of
the Cascades, setting the stage for above for well above normal
temperatures by the end of the week. Guidance shows good
agreement on highs rebounding to near seasonal norms in the 70s
in the lowlands on Wednesday and then into the 80s by Thursday.
Heat will peak across the area Friday into Saturday as the ridge
continues to strengthen. Models continue to converge on highs
in the upper 80s to low 90s, with NBM probabilistic guidance
indicating a 50 percent chance for temperatures to reach 90
degrees in Portland on Friday, decreasing with southward extent
to around a 10 percent chance in Eugene. However, chances to
reach 95 degrees are only around 10 percent in Portland and near
zero in Eugene, underscoring the increasing confidence on the
range of temperature outcomes. Probabilities decrease on
Saturday, with around a 20 percent chance to hit 90 at PDX and
lower probabilities elsewhere. Given that the ridge is setting
up a bit farther east than in previous forecast cycles, the
other forecast concern in this timeframe will be the potential
for a few thunderstorms to develop along the Cascades Friday and
Saturday afternoon as the region remains in southwest flow
aloft, allowing a few embedded disturbances to brush the area.
Currently carrying a slight chance of thunderstorms in the Lane
County Cascades on Friday and as far north as Mount Jefferson on
Saturday. Temperatures trend back downward as the ridge breaks
down on Sunday, but guidance does keep temperatures above
seasonal norms into early next week as WPC ensemble clusters
continue to favor ridging nosing back into the area from the
Pacific in the extended term. /CB

&&

.AVIATION...A frontal system will push through the region tonight,
bringing another round of rain and lowered cigs. Expect cigs to fall
to IFR/MVFR along the coast after 09-11z Tue and MVFR for Willamette
Valley locations after 12-13z Tue. Guidance suggests that the front
will move inland by 15z Tue. Afterwards, expect post-frontal showers
throughout the day while maintaining predominately MVFR cigs (IFR or
lower at the coast). Showers are expected to be light and not cause
significant visibility issues.

Winds tonight will be southerly and gust up to 30 kt along the coast
and 20-25 kt inland. By late tomorrow (Tue) afternoon, winds will
shift more southwesterly and gradually weaken. Will note that there
is potential for wind speed shear along the coast between 06-15z Tue
as southwest winds around 2000 feet strengthen to around 40-50 kt.

PDX AND APPROACHES...Mostly low-end VFR conditions until the frontal
passage around 13-15z Tue. After that, expect MVFR cigs with post-
frontal showers and gusty southerly winds through 21-23z Tue. Late
Tuesday afternoon/evening, cigs will begin to improve to VFR
thresholds with decreasing showers. Winds will also gradually weaken
and turn more southwesterly.     -Alviz

&&

.MARINE...Another frontal system quickly approaching the coastal
waters will bring increased southerly winds with gusts up to 35 kt
overnight into early Tuesday morning. Will maintain the Gale Warning
for coastal waters north of Cape Foulweather, including the Columbia
River Bar. Small Craft Advisories continue for the zones south of
Cape Foulweather through Tuesday night. Seas remain steep and choppy
at around 10 to 12 feet through Tuesday. An incoming northwesterly
swell will likely cause seas to build to around 12 to 14 feet
Tuesday night through Wednesday.

High pressure builds midweek for more settled conditions. Expect a
summer type pattern with high pressure offshore and a thermal trough
along the coast, bringing northerly winds gusting to 25 kt at times
through the end of the week. Seas around 8 to 10 ft on Thursday
likely to subside to around 6 ft on Friday. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ210-
     251-252-271-272.

     Small Craft Advisory from 8 AM Tuesday to 5 AM PDT Wednesday
     for PZZ210-251-252-271-272.

     Gale Warning until 8 AM PDT Tuesday for PZZ210-251-252-271-272.

     Small Craft Advisory until 5 AM PDT Wednesday for PZZ253-273.
&&

$$

www.weather.gov/portland

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