447
FXUS66 KPQR 152150
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
249 PM PDT Wed May 15 2024

.SYNOPSIS...High pressure is beginning to break down as a weak
trough begins to ascend from the Gulf of Alaska on Thursday.
While a pattern shift is in store, precipitation will be
minimal. Zonal flow follows which will keep the weather mild and
dry.

&&

.SHORT TERM...Now through Friday...Marine stratus is has burned off
for the most part, with the exception of some areas near the central
coast. Winds remain breezy at the coast, with NW gusts up to 25-30
mph, but all inland areas are seeing fairly light winds. High
pressure continues, but is in the process of moving out of the area.
The rest of the week sees slowly cooling temperatures, with some very
insubstantial showers possible in SW Washington and the northernmost
parts of Oregon as a trough slowly descends from Vancouver Island.
Highs today will be around the low 80s in the Willamette Valley, but
these drop closer to 70 on Thursday as the trough begins to impact
the area.

Thursday sees more of a shift to onshore flow, further supporting
cooler temperatures. Any showers accompanying the trough will be very
light and insubstantial, and most areas should still just remain dry.
With the switch to onshore flow, winds will increase through the
Gorge as west winds pick up. By Thursday evening, wind gusts along
I-84 will gust up to around 40 mph, with exposed areas at higher
elevation could reach closer to 50 mph. These will begin to calm by
late morning Friday. Friday`s temperatures will be a few degrees
cooler than Thursday, and there is around a 15% chance of some light
rain showers in SW Washington only as the trough continues to
approach. /JLiu

.LONG TERM...Saturday through Tuesday...Zonal flow begins to settle
in, ahead of the next trough that looks to arrive by Sunday.
Temperatures will settle out and stay fairly consistent through
Saturday, maybe a degree or two cooler each day. Another low
pressure system will move over Canada extending a trough over
the west. This trough will bring another round of precipitation
and a gradual cool down. The ridging to the east though will
cause winds to amplify. Through the Columbia River Gorge we
could see some gustier winds on Saturday.

NBM ensemble guidance is beginning to skew more towards the trough
beginning to enter the area on Sunday, though uncertainty remains as
to how long it will last. However, 75th percentile temperatures from
Sunday through Tuesday have lowered to around 65-70 degrees. WPC
Cluster guidance shows 60% chance of relatively stronger ridging
remaining in the area through Tuesday, while the remaining 40% show a
return to more zonal flow. Seems slightly more like that we skew
towards a slightly more active pattern through mid next week. /JLiu

&&

.AVIATION...High pressure will bring mainly VFR flight conditions
today as mostly clear skies remain in place over the region. The
exception is along the coast where an LIFR to IFR marine stratus
is clinging to the beaches. Will see stratus push into the west
slopes of the coast range this evening with IFR conditions
continuing through Thursday morning. North to northwest wind
gusting around 25 kt along the beaches through about 06Z Thu.

Inland VFR through most of the night but with onshore flow expect
to see MVFR cigs moving up the lower Columbia River into southwest
WA, and north Willamette Valley after 10Z Thu. This pattern of
northwest winds in the low level suggest a stratus deck could
back building from near the west end of the Gorge to the PDX
terminal area. Details on flight conditions for PDX below, but for
the rest of the Willamette Valley there is 30-40% chance for MVFR
12-18Z Thu reaching KUAO and KSLE, and 15-18Z in the KEUG area.

PDX AND APPROACHES...VFR flight conditions are likely to continue
over the next 24 hours under mostly clear skies. That being said,
there is a 50-80% chance for MVFR cigs 12-18Z Thu, and a 20-30%
chance for IFR cigs 11-16Z Thu in the PDX area. VFR expected to
prevail after 18Z Thu. Winds will be typical summer-like pattern
with northwest wind 8-12 kt through the evening hours (about 06Z
Thu) then easing.
/mh

&&

.MARINE...High pressure continues over the waters today, resulting
in a typical summertime northerly wind regime. Similar to
yesterday, northerly winds will peak in strength during the
afternoon and evening hours with gusts to around 25 kt to the
north of Cape Foulweather and gusts to 30 kt to the south.
The Small Craft Advisory for all marine zones to continue through
the afternoon for the northern waters, through the evening for
the central waters, and through tonight for the southern waters.
Winds should temporarily fall below small craft criteria on
Thursday as a weak cold front moves inland, but should increase
behind the front Thursday evening with gusts to around 25 kt for
the northern waters, so have issued a Small Craft Advisory there
for Thursday afternoon and night.

Seas will generally remain between 5 to 9 feet over the next few
days as a primary northwest swell continues along with northerly
wind waves. /mh -TK

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 5 PM PDT this afternoon for PZZ251-
     271.

     Small Craft Advisory from 2 PM Thursday to 11 AM PDT Friday for
     PZZ251-271.

     Small Craft Advisory until 11 PM PDT this evening for
PZZ252-272.

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

$$

www.weather.gov/portland

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland