365
FXUS66 KPQR 151830 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1130 AM PDT Sun Sep 15 2024

Updated Aviation Discussion


.SYNOPSIS...
A fall-like weather pattern will continue over the
next week. Mainly dry on Sunday with increasing sunshine. Dry on
Monday with sunshine and warmer temperatures. Rapid change to cool
and wet conditions Tuesday into Wednesday as a strong frontal system
brings widespread rain to the area. Drier and warmer conditions
return again late in the week.

&&

.SHORT TERM...Now through Tuesday night...Mainly dry on Sunday
with increasing sunshine. Cannot rule out a stray shower or two
at the coast and over the southern Willamette Valley. Locations
to the north of that should stay dry through the day. Expect
mild temps with highs around 70 degrees across the lowlands.

Becoming warmer on Monday with plenty of sunshine as dry northeast
flow develops aloft on the backside of a low to the southeast. Monday
is still shaping up to be the warmest day of the week, and the latest
iteration of the deterministic NBM has ticked up a degree or two. The
NBM now suggests highs in the mid to upper 70s, except 60s at the
coast. There is still a chance for high temps in the lower 80s
(15-30% from Portland to Eugene). Overall Monday will be a great day
for outdoor activities, especially given the rapid pattern change to
cool and wet weather come Tuesday. This is when models and their
ensembles have consistently showed widespread rain developing across
all of northwest OR and southwest WA as a stronger frontal system
moves over the coastal waters and pushes inland. Chances for rain
remain near 100% with this system. Expect rain to begin at the coast
Tuesday morning before pushing into the Willamette Valley,
Portland/Vancouver metro and Cowlitz Valley during late morning to
early afternoon hours.

Post-frontal showers will then continue Tuesday night. Total rain
amounts will likely wind up between 0.25-0.50 inches, except
0.50-0.75 inches at the coast and 0.50-1.0 inches in the Cascades and
Coast Range. Probabilities for rain amounts over one inch are around
10-15% from Kelso to Portland to Salem to Corvallis. Probabilities
increase to 30-50% from Junction City to Eugene-Springfield to
Creswell and Cottage Grove. 30-50% chance for most locations along
the coast, and a 50-65% in the Coast Range and Cascades. Regardless
of exact rain amounts, enough will fall to result in a significant
damper on fire activity. In regards to temps, highs will struggle to
reach the mid 60s on Tuesday, around 10-13 degrees below average for
this time of year.  -TK


.LONG TERM...Wednesday through Saturday...While there will be
some showers lingering in the area on Wednesday, suspect convective
activity will be on the decrease as weak high pressure builds in
behind Tuesday`s weather system. Model soundings depict increasing
sunshine Wednesday, allowing temps to warm back to around 70 degrees.
Similar temps likely on Thursday and Friday, albeit a few degrees
warmer. Most model guidance depicts shortwave ridging late in the
week, resulting in dry conditions. NBM PoPs back this up and are
under 10-15% both days. Offshore flow attempts to develop Friday night
or Saturday, likely bringing even warmer temperatures to the region
heading into next weekend. In fact, NBM probabilities for high temps
of 80 degrees or warmer climb to 20-25% by next Saturday.  -TK


&&

.AVIATION...Some isolated showers linger over the area but clouds
are beginning to lift and erode. Areas with the densest and MVFR
CIGs are along the southern portions of Washington and along the
Cascades. Much of the cloud cover is cumulus signifying the mixing
nature of the airmass. Will see VFR conditions persist through the
day as high pressure builds. Overnight temperatures are not
decreasing enough the fog is a concern inland, but cannot rule it
out along the coast.

PDX APPROACHES...General VFR through the next 24 hours with a few
periods of MVFR CIGs with passing clouds. Will see steady
improvement through the day. Winds may become breezy in the
afternoon, but gusts not expected to exceed 20 kt. -Muessle

&&

.MARINE...
High pressure over the outer waters will build tonight
into Sunday. As such, will maintain the northerly pressure
gradients, with gusty north winds Sunday night. Small Craft
Advisory continues for late this afternoon into Monday, where
have gusts 20 to 25 kt. Does appear will get some gusts in similar
range closer to shore, but suspect most of these will be stay
just offshore. Seems gradients relax early Monday am with Small
Craft Advisory winds continuing over the outer zones through the
afternoon. Overall, seas stay in 5 to 8 ft through Monday, with
highest seas well offshore.

Then, a taste of fall arrives Tuesday. A potentially strong front
will push across the waters Tuesday as it elongates/weakens over
the coastal waters. Winds not really turning to southerly (as do
with most fronts), but may briefly get burst of west to southwest
winds of 20 to 25 kt with the frontal passage. Models still vary
some on the timing/strength of this system, so will see how things
shape up as get closer in time to Tuesday.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 5 AM PDT
     Monday for PZZ252-253.
     Small Craft Advisory from 5 PM this afternoon to 5 PM PDT
     Monday for PZZ272-273.
&&

$$

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