606
FXUS66 KPQR 032215
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
315 PM PDT Mon Jun 3 2024

.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...Northwesterly flow aloft becoming westerly as moist
onshore flow persists through Tuesday. Predominately VFR in the
post frontal environment with scattered showers and gusty
southwest winds at the surface. Showers gradually diminishing this
afternoon, but the next frontal system begins to push in this
evening with light rain and lowering CIGS. Expect conditions to
deteriorate to MVFR along the coast after 00Z, and inland by
around 04Z Tuesday. Winds are expected to remain breezy, though
backing to more southerly direction. Strongest winds expected
along the coast with gusts up to 30 kt. May see some low level
wind shear develop overnight into Tuesday morning between 06Z-18Z
as southwest winds increase to around 35-40 kt at 2000 feet.

PDX AND APPROACHES...VFR with decreasing rain showers this
afternoon. Conditions expected to deteriorate to MVFR late this
evening as another frontal system brings rain and lower CIGS.
Chances for MVFR increase to above 50% after 04Z Tuesday,
continuing through Tuesday morning. Southwest winds around 12-16
kt expected through this evening, then becoming more southerly
with gusts up to 20 kt. Low level wind shear also possible after
06Z Tuesday as southwest winds around 2000 ft increase to around
40 kt. /DH

&&

.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.
     Gale Warning from 11 PM this evening to 8 AM PDT Tuesday for
     PZZ210-251-252-271-272.
     Small Craft Advisory until 5 PM PDT Tuesday for PZZ253-273.
&&

$$

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