326
FXUS66 KPQR 282201
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
301 PM PDT Thu May 28 2026

.SYNOPSIS...Shower and thunderstorm chances continues this
afternoon and evening. Strong to severe thunderstorms are
possible over the Cascades and Hood River County. There are
decreasing chances of thunderstorms over the valley tonight. As
thunderstorms move west of the Cascades, they are likely to
weaken into showers. Showers continue into Friday with cooler
conditions into Saturday. Dry weather with increasing
temperatures Sunday into early next week.

&&

.DISCUSSION...Thursday afternoon through Wednesday...The main
focus of the forecast is the chance for severe thunderstorms
over the Cascades today with the best chances around Hood River
County and east of the Cascades. There is a Severe Thunderstorm
Watch in effect for Hood River County until 8 PM tonight, though
thunderstorms chances continue through 10 PM tonight.
Thunderstorm chances have diminished significantly over the
valley for this afternoon and evening with only a 5-10% chance
that storms moving off of the Cascades hold together.

Now for the deeper analysis. A large upper closed low pressure
system remains centered over California while an upper trough
deepens in the northeastern Pacific. The PacNW remains
sandwiched between the two in an area of convergence as a
shortwave along the CA low is moving northwest into the region
today. REFS and HREF guidance along with forecast soundings
indicate CAPE values could increase to 1200-1600 J/kg over the
Cascades, especially north of Lane County and peaking around
Hood River and Skamania Counties. Additionally, 0-6 km shear
values are expected to peak around 35-40 kts over the Cascades.
Guidance indicates the best conditions for severe thunderstorms
will be over Hood River County and possibly into southern
Skamania County where CAPE will be highest. Strong wind gusts of
60 mph and large hail around 1 inch are possible in stronger
thunderstorms, as well as heavy rain.

SPC mesoanalysis at 2 PM PDT indicates MUCAPE over 1000 J/kg
and 0-6 km shear over 30 kts with PWAT values over 1 inch over
the Cascades. One difference from previous forecasts is the
location of the shortwave remains just slightly farther east,
which means the lift for thunderstorms over the Cascade crest
and west has moved later in time compared to previous forecasts.
Instead of initiating late this morning, we are just now seeing
initiation over the Skamania/Yakima County border. Better
conditions for severe thunderstorms are being observed over
eastern Oregon, and models indicate that these isolated storms
forming over eastern Oregon will eventually become more linear
this afternoon as they move west through central Oregon and into
the Cascades. Since this is now occurring later in the day, the
convective potential will be waning as surface heating cools.
This will likely prevent thunderstorms from being able to hold
together as they move west of the crest. Could still see
thunderstorms in the western foothills, but they likely will
weaken significantly before moving over the valley. Chances for
thunderstorms over the valley have diminished to only 5-10% with
light showers most likely outcome, mainly along and east of I-5.
This also means the concern for heavy rainfall over the valley
has diminished, though this still remains a concern over the
Cascades. REFS and HREF indicate hourly rain rates of 0.3-0.5
inches per hour with many members indicating rain rates of
0.6-0.8 inches per hour. These rates could cause localized
poor-drainage flooding and ponding, and would also raise
concerns for landslides in more susceptible terrain if heavier
rates occur.

Friday brings a notable change as the CA low finally shifts
east and broader troughing from the northeastern Pacific deepens
into the PacNW. Shower chances persist into Friday morning,
then become more focused over the Cascades by the afternoon,
becoming dry by Saturday. Temperatures drop back into the mid
60s for many interior lowland locations Friday into Saturday.

Looking beyond the cool-down, guidance favors drier conditions
into next week with another brief warming trend Sunday into
Wednesday. Temperatures rise back into the low 70s Sunday, low
to mid 80s Monday, and upper 80s to low 90s by Tuesday.
Temperatures begin falling Wednesday, though still remain warmer
in the upper 70s to low 80s. Current probabilistic guidance
has somewhat decreased chances of temperatures reaching 90+
early next week. Chances on Monday are now 10-25% around and
north of Salem. Tuesday still looks to be the warmest day
with 30-50% chances around and north of Salem. There`s only a
5-10% chance in the Portland metro area on Wednesday. HeatRisk
has decreased to Minor for Monday and Wednesday with Moderate
HeatRisk for the Portland/Vancouver metro area and Lower
Columbia and Cowlitz valleys on Tuesday. Probabilities for Major
HeatRisk are now less than 5% each day. -03/12

&&

.AVIATION...Onshore surface flow continues along the coast,
supporting MVFR/IFR stratus which is expected to persist through
the TAF period. Could see a brief break late this afternoon as the
stratus recedes just offshore but this would be short lived. VFR
conditions inland through the evening expected with high level
clouds streaming in from the east. Chances for MVFR CIGs at inland
terminals increase to 30-60% after 06-08Z Fri as wrap-around
moisture brings rain showers to the airspace. Mostly westerly to
northwesterly winds increasing after 21-23Z to 10-15 kt and
persist through at least 06Z Fri, bringing gusts up to 20 kt at
most terminals, possibly up to 25 kt at coastal terminals.

The thunderstorm threat has decreased for most of the area
outside of the Cascade crest, trending toward an organized band
of showers. A period of breezy/erratic winds are still possible in
this scenario however. Thunder remains out of the TAFs at this
time.

KPDX AND APPROACHES...VFR conditions through at least 06Z Fri.
Beginning around 06-09Z Fri, there is another 10-20% chance of
MVFR CIGs. The thunderstorm threat has decreased but a band of
organized showers remains possible this evening.  ~19/12

&&

.MARINE...High pressure offshore will maintain breezy north to
northwesterly winds across the coastal waters through Friday.
Expect frequent gusts to around 20-25 kt. Seas around 10 to 12 ft
will persist through the overnight hours. Wave heights then
gradually subside back down to around 7 to 8 ft by Friday
evening. A Small Craft Advisory for all coastal waters including
the Columbia River Bar will remains in effect until 11 AM Friday.
High pressure is expected to strengthen this weekend across the
coastal waters leading to a return of breezy northerly winds on
Sunday. There is a 50-80+% for wind gusts to reach Small Craft
Advisory criteria Sunday afternoon, with the higher probabilities
south of Cape Falcon down to Florence. Seas continue to drop to
around 5 feet by Sunday night. -19/12

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.

WA...None.

PZ...Small Craft Advisory until 5 AM PDT Friday for PZZ210-251>253-
     271>273.

&&

$$

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