609
FXUS66 KPQR 201001
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
301 AM PDT Fri Sep 20 2024

.SYNOPSIS...Little change in the last weekend of summer, as high
pressure offshore will maintain pleasant days and cool nights. A weak
front will push across the region later Sunday and Monday. Then, high
pressure builds inland, with bit of warmer weather for middle of next
week.
&&

.SHORT TERM...(Today through Saturday)...
Upper level trough moving across the Pacific NW early this morning.
While am not expecting any rain, will have an uptick of onshore flow
across the region. This will allow for breezy west to northwest winds
over the higher terrain, and through the Columbia Gorge.

Otherwise, high pressure offshore will build inland today into
Saturday. After area of morning clouds, mainly along the coast and
inland valleys (Cowlitz and lower Columbia into the lower
Willamette), will have partly to mostly sunny skies. Temperatures
will be down a few deg as compared to those yesterday.

Clearing tonight, and cool. Many areas will drop back into the
mid-40s overnight for lowlands, and 30s across the higher Cascades.
After the cool start on Saturday, will see another quite pleasant
late summer day, with temperatures back into the 60s along the coast,
and lower to middle 70s for interior valleys. Looks like Mother
Nature is giving us a nice last day of summer. /Rockey

.LONG TERM...Sunday through Thursday...Sunday looks to feature
a fairly zonal upper level flow regime across the Pacific
Northwest, maintaining dry and seasonable weather with inland
high temperatures in the mid to upper 70s. A weak upper level
disturbance skirting the Canadian border will bring a slight
chance of rain across southwest Washington and far northwest
Oregon Sunday evening into Sunday night, but expect most
locations to ultimately remain dry. Medium range guidance
continues to converge on a warmer and drier solution for the
start of next week, with ensemble clusters and 12z deterministic
models both showing good agreement on an upper level ridge
building over the Pacific Northwest on Monday and shifting
inland on Tuesday. This will bring well above normal
temperatures to the area on Tuesday as highs climb into the mid
to perhaps upper 80s in the interior valleys. The potential for
temperatures higher than that appears rather minimal as latest
probabilistic guidance gives only about a 10 percent chance to
reach 90 degrees in the Portland area and closer to a 30 percent
chance from Salem to Eugene. Any heat concerns look to be
limited to just Tuesday as the ridge shifts east of the region
and temperatures trend back down mid to late week. Guidance also
depicts a short lived period of offshore flow developing late
Monday into early Tuesday. Not overly concerned about east winds
at this time given the progressive nature of the pattern and
fairly modest offshore pressure gradients, but will be something
worth keeping an eye on for those in the fire weather community
as roughly half of European ensemble members depict wind gusts
reaching 25 mph in the vicinity of the Columbia River Gorge late
Monday into early Tuesday. Still some uncertainty beyond
Tuesday as the ridge shifts east to the Rockies, with guidance
remaining split on the strength and timing of an upper level
trough arriving Wednesday into Thursday. NBM mean solution
depicts temperatures moderating to near seasonal norms with
chance to slight chance PoPs returning to coastal and northern
parts of the area during the middle of the week. /CB


&&

.AVIATION...High pressure continues to build over the region
through the weekend. High clouds aloft will be the determining
factor to our overnight CIGs and VIS. Cloud cover will keep
visibility favorable as it will restrict the evaporative cooling.
Thus expecting the VIS to remain VFR. CIGs on the other hand are
a bit of a different story. There is currently a scattered layer
at 3000 ft AGL, but skies are beginning to fill. Areas that see
MVFR CIGs will improve after 20Z Friday. Winds remain onshore.

PDX APPROACHES...High end MVFR CIGs through the morning. Less than
a 10% chance of IFR CIGs/VIS but it will mainly come down to the
dewpoint depression and radiational cooling. As the sun rises
clouds will clear to VFR. No other concerns.
-Muessle

&&

.MARINE...Minimal changes in the marine environment as high
pressure lingers over the area. Winds will be northwesterly
through much of the week with the gustier conditions through the
next 12 hours. While the Small Craft Advisory expires this
morning, there may still be gusts up to 25 kt in the outer waters
west of 30NM through 0700. Given they will not be widespread have
not extended the advisory. Winds will slowly ease with gusts up to
20 kt for the foreseeable future due to the high pressure.

On Sunday, a weak front will move over the waters. This front is
not overly strong so it will have minimal impact other than
showers north of Tillamook.-Muessle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 4 PM this afternoon to 10 PM PDT this
     evening for PZZ210.

     Small Craft Advisory until 5 AM PDT early this morning for
     PZZ271>273.
&&


$$

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