744
FXUS66 KPQR 130954
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
252 AM PDT Thu Jun 13 2024

.SYNOPSIS...
High pressure offshore maintains seasonably warm and
dry conditions through Thursday. Low pressure then brings cool
and showery weather Friday into the early part of next week,
with a slight chance of thunderstorms Saturday into Sunday.
Temperatures look to rebound near or above seasonal normals later
next week.


Key Messages...

-  Increasing onshore flow later this afternoon.

-  Cooler, with increasing clouds for Friday. Chance of showers
   along the coast (Tillamook northward) and west Washington.

-  Cool, with showers for Saturday through Monday. A small
   chance (15-25%) of afternoon/evening thunderstorms on Sat.

&&

.SHORT TERM...(Today through Friday night)...Not much change this
morning, as still have high pressure offshore and dry north to
northwest flow aloft. Overall, another pleasant mid-June day on tap
for the region today, with highs in the 60s along the coast, and mid
70s for inland valleys. A few spots in the Willamette Valley may
reach 80 this afternoon. But, not all that sold on that possibility.
Main reason will be the increasing onshore flow this afternoon.
Onshore pressure gradients will tighten this afternoon, as surface
high offshore moves toward the coast. This will increasing the cooler
marine air invasion through the gaps in the Coast Range and Willapa
Hills this afternoon into this evening. So, temperatures will likely
peak in the 2 to 4 pm timeframe, then drop back a bit as the marine
air spreads into the interior lowlands.

May be breezy in the usual spots in the western Willamette Valley as
the marine air spreads inland. Such spots like the Philomath gap, Van
Duzer Corridor, Siuslaw River gap to west of Eugene, will see gusty
west to northwest winds later this afternoon, with gusts 20-25 mph
for a time. In addition, will see up tick of west to northwest winds
(though not as strong) along the Columbia River from Portland to
Kelso. Breezy west winds likely in the mid-Columbia River Gorge from
Bonneville eastward as well later today into tonight.

Expect a pattern shift back towards cooler and cloudier weather
on Friday as an upper level trough currently over the Gulf of
Alaska descends upon the Pacific Northwest. This will drop
temperatures back near or slightly below seasonal norms with
highs in the upper 60s or low 70s and also bring a chance of
showers as a weak front moves through the area. Shower chances
look to be generally confined to areas along and north of a
Lincoln City-Portland-Mt St Helens line through Friday evening
before more widespread shower activity spreads across the area
Friday night. Model QPF remains on the light side, ranging from
0.25 to 0.50" over the higher terrain, but generally a tenth of an
inch or less for all other locations for Fri through Sat am.

.LONG TERM...Saturday through Wednesday...WPC ensemble clusters
remain in strong agreement on maintaining upper level troughing
and a resulting cool, cloudy and showery pattern over the
Pacific Northwest this weekend through the early part of next
week. This is reflected in ensemble temperature forecasts which
keep the area below normal with highs in the 60s through at
least Monday. Cold air aloft will maintain showery conditions
into Tuesday, though these look to be mainly spotty in nature
with model QPF amounts remaining light through the period.
Guidance indicates a 15-25 percent chance for a few rumbles of
thunder across the north both Saturday and Sunday afternoon,
which will largely be dependent on if there are enough sun
breaks to allow for adequate destabilization. Temperatures look
to rebound into the 70s next Tuesday and Wednesday as the
majority of ensemble clusters depict the trough starting to
shift east of the region by midweek. /CB

&&

.AVIATION...VFR conditions continue to dominate, with fairly clear
cloud cover for most terminals. The southern coastal terminals
(KONP) see a 10-30% chance of some low scattered cloud cover
developing in the latter half of the night, clearing by 20z Thu.
Regardless, no chance for MVFR ceilings as this is expected to be
scattered and patchy cloud cover.

Light northwesterly flow is in place, with winds generally below 7
kts at all terminals. Winds pick up slightly through Thursday
afternoon, with top winds up to 25kt inland and 30kt at the coast.
These will decrease by 05z Thu, becoming fairly light afterwards.
/JLiu

PDX AND APPROACHES...Predominantly VFR and clear skies throughout
the TAF period. Weak northwesterly winds up to 7 kts currently,
increasing around 17-18z Thu. These peak in the evening, with
northwesterly gusts up to 20 kts possible around that time. Winds
decrease again going into Thursday night back to weak winds. /JLiu

&&

.MARINE...Wind-driven Small Craft Advisory continues until
Thursday night for the inner and outer waters. Seas are currently
around 7-9 feet at 9 seconds, with northerly winds gusting up to
25 until Thursday evening, when they begin to decrease. Winds
decrease enough to end the SCA at that time. Seas will have
settled to 5 to 7 ft around this time, but may remain choppy. Next
front will arrive late Friday, shifting winds back to westerly at
10 to 15 kt for late Friday into early Sunday.
-JH/JLiu

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 PM PDT this evening for
   PZZ251>253-271>273.
&&


$$

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