828
FXUS66 KPQR 290447
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
947 PM PDT Fri Jun 28 2024

.UPDATED AVIATION DISCUSSION...

.SYNOPSIS...
Aside from some light drizzle across the northern
portions of the CWA late Saturday into Sunday, onshore flow will
maintain near average temperatures into early next week. There is
30-40% chance that stronger high pressure offshore will shift over
the region towards the end of next week and bring our hottest
temperatures of the Summer so far.

&&

.SHORT TERM...Tonight through Sunday...Weak upper level
troughing under low level onshore flow will keep the area mainly
dry with temperatures pretty darn close to average for this
time of year through the weekend. A passing shortwave trough to
our north will clip the region and perhaps deepen the marine
layer enough to wring out some drizzle and light rain along
mainly the coast, Coast Range and Cascades north of a line
extending between Mt Jefferson and Newport late Saturday into
Sunday. NBM probabilities for rain only climb into the 15-30%
range for any given 6-hour period late Saturday into Sunday
along the north coast and higher terrain. All in all, it looks
like rather average and benign weather for late June. /Neuman


.LONG TERM...Monday through Friday...As the upper level shortwave
trough moves east of the region early next week, WPC clusters are in
very good agreement of upper level ridging building over the eastern
Pacific. Ensembles are in good agreement that zonal flow aloft and
low level onshore will couple to bring a continuation of temperatures
near to slightly (a few degrees) above average for areas away from
the coast through midweek.

Uncertainty in the forecast begins to grow dramatically midweek as
ensemble members begin to diverge substantially on potential
scenarios. While nearly all of the ensemble guidance has above
average 500mb heights over the Pacific Northwest by Thursday, about
25% of the ensemble guidance suggests an upper level trough will
either be approaching the region from the northwest or a different
shortwave trough will be lingering across the northern Rockies to
keep temperatures across the area near average. The rest suggest a
pattern conducive for above temperatures, but with varying degrees of
heat. At this point, it appears there`s a 25% chance that
temperatures climb to 90F by Thursday across inland valleys with the
probabilities rising to 50% on Friday. There is even a low
probability (10%) of 100F temperatures by Friday. The NBM
deterministic forecast is on the warm side of the probability
distribution come next Friday, but not enough to change it so have
left the forecast as is. /Neuman

&&

.AVIATION...High pressure continues to shift eastward as a weak
upper-level trough approaches the coastline expected to clip the
region to the north on Saturday. Fortunately VFR conditions likely
persist at inland sites through the TAF period with CIGS
eventually lowering to ~5kft by Saturday evening. That said, the
same can`t be said for the coast where MVFR conditions develop
between 20-23z due to the aforementioned weather disturbance,
deteriorating further to IFR cigs/vis by Saturday evening
although confidence is only moderate regarding the exact timing at
KONP/KAST.

PDX AND APPROACHES...High pressure shifting eastward will continue
to facilitate VFR conditions locally with typical diurnally
driven northwest to northerly winds through 00-06z Sunday. CIGS
gradually decrease through the period but will remain VFR.
-Schuldt

&&

.MARINE...
Weak high pressure over the northeast Pacific with lower
surface pressure over California and the Great Basin will more or
less maintain itself into next week. A weak front will temporarily
try to clip the waters tonight into Saturday and turn winds more
out of the west. Otherwise, expect north to northwest winds
across the waters with the strongest winds generally off the
central coast of Oregon and lighter winds farther north. Winds
will generally peak in the afternoon and evening hours each day.
Pressure gradients appear increasingly likely to increase by early
to mid next week so that there is a >90% chance that northerly
wind gusts of 25-30 kt spread northward across the waters. This
will in return develop steep wind driven seas of 5-8 ft with a
dominant period of 7-8 seconds by Tuesday or Wednesday. /Neuman

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

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