851
FXUS66 KPQR 031346 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
646 AM PDT Wed Jun 3 2026

Updated aviation discussion.

&&

.SYNOPSIS...Longwave trough moves over the region today
increasing onshore flow and bringing chances for light rain to
the terrain. Cooler temperatures expected through the weekend. A
low pressure system in the northeast Pacific shifts southward
Friday night into Saturday which has higher probabilities for
accumulating rainfall through Sunday. The system remains active
through Tuesday.

&&

.SHORT TERM...Now through Friday Night...After a warm Tuesday,
today continues to shape up to be cooler and much more moist. A
negatively tilted trough extending from a closed low pressure
system in the northeast Pacific will advance over the area.
Satellite imagery shows the high stratus shield over much of the
region with showers beginning to show up on radar over the
waters and the coast. While radar shows these showers right now,
there hasn`t been precipitation reaching the surface due to it
evaporating before reaching the ground. Will need a little bit
more time for the atmosphere to saturate enough to produce
accumulating rain. With this rain, the flow will become south to
southwesterly. In areas that are north-south aligned like the
coast and the Willamette Valley we could see isolated gusty
winds though generally the breezier winds will be concentrated
to the coast. With the overall pattern in place, precipitation
chances are quite low with the highest chances for rain
occurring this morning along the coast. There is between a
15-30% chance of rain along the coast this morning with less
than a 15% chance elsewhere. In the most current forecast the
Cascades have been left out of the rain. However, some higher
resolution models like the NAM Nest show more widespread rain
without a specific trend. The bulk of the rain will occur
between 5AM to 3 PM.

Behind this trough, weak shortwave ridging will maintain dry
and sunnier conditions on Thursday. Seasonable temperatures in
the mid 70s inland and in the 60s along the coast are expected
with less than a 5% chance of isolated light rain showers.

Friday is going to be a bit of a transitional day as the low
pressure system in the northeast Pacific drops further
southward towards the Washington coast. Wile organized aloft, at
the surface, the low pressure is less realized and therefore
sensible weather may be a bit more chaotic. A component that
should be considered is the amount of energy associated with
this system though which, if it manifests, could mean we see
more convective activity. The Extreme Forecast Index (EFI) from
the ECMWF shows climatologically abnormal CAPE on Friday and
it`s generally concentrated to the coast and marine waters.
Divergent flow combined with enhanced vorticity advection and
cooler air aloft may increase chances for thunderstorms Friday
afternoon and evening. Strengthening onshore flow will cause
winds to increased within the Columbia River Gorge and the Upper
Hood River Valley. It is not unreasonable to see gusty winds
greater than 30 mph within those areas and along the peaks of
the Cascades. The NBM shows the mean wind gusts in the Upper
Good River Valley around 40 mph while the 90th percentile (the
high end solution) is around 45 mph. There may be somewhat of a
computing bias in these areas, but given the pressure gradient
and the amount of support in this system it isn`t unreasonable
to expected enhanced winds Friday afternoon. -27


.LONG TERM...Saturday through Tuesday...The low pressure system
shifts inland through Saturday with a bulk of the rain falling
in the morning. Again there is quite a spread with potential
accumulation with the 10th percentile (driest ensembles) showing
0.00 inch of rain and the 90th (wettest solution) is closer to
0.25-0.50 inch. Overall though, the upper end of that range has
decreased each day. This is likely due to the more northerly
track of the system and thus we sit on the southern edge where
less of the moisture is. At that time though we are sitting in
the right entrance region of the jet streak which is often
associated with more energetic weather. Combine this with the
divergent flow, rain, and orographic effects, cannot rule out
another threat for thunderstorms in the afternoon. Of the two
days (Friday and Saturday), Saturday is the most potent day with
CAPE exceeding 150 J/kg in some locations.

Transitioning into Sunday we will see some post frontal showers
with an inverted trough aloft. However, those conditions will be
short lived as yet another low pressure system is next up to bat
late Sunday into Monday. Looking at the ensemble low locations,
there is quite the spread between potential outcomes and the
ECMWF ensembles show the concentration of possibilities slightly
further south than the GFS ensembles. There is a great level of
uncertainty in exactly what this will mean specifically, but the
overall general pattern will favor onshore flow, cool
temperatures, and potentially more rain which will last through
Tuesday. -27


&&

.AVIATION...Radar imagery shows showers spreading inland though
they will be light initially. They will intensify over the next
few hours, but quick subside through the afternoon. Generally
VFR conditions with pockets of MVFR with passing showers except
along the coast where IFR CIGs persist. There may be some
improvement in the afternoon due to mixing with the passage of
the front, but overall, if it does improve from IFR, it will
only be to MVFR. Southwesterly winds will dominate over the next
24 hours but will shift to the west after 06Z Thu. Gusty winds
expected with showers which may develop shear like conditions.

KPDX AND APPROACHES...Generally VFR with less than a 10% chance
of MVFR CIGs. If they do form, they will develop within showers.
Light winds will transition to the southwest by 18Z Wed, then
become westerly late in the forecast. Confidence is low in
regards to rainfall totals and impacts. -27

&&

.MARINE...Southwesterly flow of 5-10 kt as a decaying front
traverses the waters this afternoon. With this frontal system,
rain is expected though will be light overall. In the passing
showers, outflow wind gusts of 20-25 kt are possible, but are
not expected to be widespread. As the front exits Wednesday
night into Thursday, the flow returns to the northwest. Seas of
4-6 ft at 10-12 seconds with a dominant northwest swell continue
through today, before a more westerly swell builds behind the
frontal passage. Seas then build to 6-8 ft at 10 seconds from
late tonight into early Thursday morning.

Generally unsettled weather looks to persist over the Northeast
Pacific through the remainder of the forecast period with
repeated systems bringing chances for further rain showers and
elevated winds, most notably from Friday night into Saturday.
Despite the active pattern, winds and seas are favored to remain
below hazardous thresholds aside from chances for wind gusts
exceeding 20 kt when brief northerly flow redevelops Sunday
afternoon and evening.         -27/36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

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