420
FXUS66 KPQR 161755
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1055 AM PDT Sat May 16 2026

Updated aviation discussion.

&&

.SYNOPSIS...Upper level troughing will maintain showers with
seasonably cool temperatures today, as well as a 10-20% chance
of thunderstorms this afternoon. Cooler temps aloft have also
allowed snow levels to fall to around 3500-4000 feet. A Winter
Weather Advisory is in place through this evening for the
Cascade passes. Drier and warmer weather returns Sunday through
next week as high pressure re-builds.

&&

.DISCUSSION...Today through Friday...Radar and satellite imagery
this morning show widespread to scattered showers moving east across
the area as low pressure near the Olympic peninsula maintains
moist, onshore flow. Broad upper level troughing over western Canada
will continue to gradually drop over the Pacific NW today
maintaining cooler temperatures aloft. A shortwave trough within the
northwesterly flow is likely to enhance shower activity this
afternoon, along with a 10-20% chance of brief thunderstorms for
northern portions of the forecast area. Any sunbreaks this afternoon
could allow daytime heating to enhance the instability to the upper
end amount (300 J/kg), but forecast soundings do show warmer air in
the midlevels creating a cap at around 500 mb which would keep cloud
top heights limited in growth.

The cooler temperatures aloft have also allowed snow levels to come
back down to around 3500-4500 ft overnight. Webcams at Cascade
passes do show some snow covered roads at Government Camp where the
temperature is around 32-33 degrees, and blowing snow at Santiam and
Willamette Passes where the temperature also sits at around 32
degrees. The probability for exceeding 6 inches of snowfall through
this evening remains at around 30-60%, though total snowfall amounts
are likely to vary due to the showery nature of the precipitation.
Highest chances for accumulating snowfall remain near Mt Hood. With
a higher sun angle in May, any daytime sunshine will likely be more
efficient in melting snow on the roads, which should help limit
impacts to drivers. But, make sure to refer to ODOT/WSDOT for the
latest road conditions. A Winter Weather Advisory remains in place
for the Cascades above 4000 ft through this evening. Total snowfall
amounts between 4 to 8 inches are possible, highest amounts near Mt
Hood. Up to 12 to 18 inches of snow is possible above 5000 to 5500
feet.

After another day of seasonably cool temperatures, expect a warming
trend to begin Sunday and continue through the middle of next week.
As the upper level trough shifts east, high pressure returns over
the region. Ensemble guidance is is general agreement that upper
level ridging builds into the NE Pacific. Latest guidance shows more
confidence in the ridge progressing eastward over the Pacific NW.
The farther east the ridge does shift over the PacNW, temperatures
are more likely to see higher end amounts, with afternoon highs
reaching the mid to upper 70s by the middle of next week. If the
region stays under more northwesterly flow aloft, afternoon temps
would be more likely to remain in the upper 60s to lower 70s. The
majority of ensemble guidance does maintain mostly dry conditions
for next week. 12/DH

&&

.AVIATION...Expecting mainly VFR conditions to prevail through the
TAF period. Scattered showers expected into the evening and a
10-30% chance for thunderstorms through the afternoon, highest
chances north to south. Any shower or storm that passes directly
over a terminal may bring a brief period of sub-VFR conditions.
For coastal terminals, northwesterly winds around 10-15 kt with
gusts to 20 kt. For inland terminals, expect westerly winds
9-12 kt and gradually shifting northwesterly towards 00Z Sun.
Wind gusts up to 20 kt will become likely beginning around 18-22Z
Sat for most terminals.

KPDX AND APPROACHES...Predominately VFR with scattered rain
showers through the evening and a chance for thunderstorms through
the afternoon. Any passing shower or storm may bring brief sub-VFR
conditions. Westerly winds around 10-12 kt northwesterly by 00Z
Sunday. -19/DH


&&

.MARINE...Breezy northwest winds continue today as surface low
pressure to the north weakens and pushes inland into western
Washington. Scattered showers continue through this evening,
with erratic and gusty winds possible near stronger showers. A
mid- period northwest swell will build seas to around 10 to 12
ft today, then gradually subsiding back below 10 ft by early
Sunday. The Small Craft Advisory remains in place for all
waters, including the Columbia River Bar, through this evening.

North to northwesterly winds return Sunday into early next week
while seas ease to around 4 to 8 ft as high pressure builds
offshore. Winds will be strongest across the central coastal
waters each afternoon and evening. Strong currents during morning
ebb tides will continue daily through Thursday, potentially
yielding steep and hazardous seas for small craft crossing area
bars through much of the week. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Winter Weather Advisory until 11 PM PDT this evening for
     ORZ126>128.

WA...Winter Weather Advisory until 11 PM PDT this evening for
     WAZ211.

PZ...Small Craft Advisory until 2 AM PDT Sunday for PZZ210-251>253-
     271>273.

&&

$$

www.weather.gov/portland

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