996
FXUS66 KPQR 141843
AFDPQR

Area Forecast Discussion...Updated Aviation
National Weather Service Portland OR
1142 AM PDT Tue May 14 2024

.SYNOPSIS...High pressure ridging returns today, maintaining
warm, dry, and mostly clear conditions through at least
Thursday. Uncertainty remains with whether or not this trend
continues over the weekend.

&&

.SHORT TERM...Now through Thursday...Satellite imagery is
showing scattered marine stratus along the Oregon coast, into
southwest Washington, and along the Columbia river. Marine
stratus will remain scattered into the morning but it is
uncertain how widespread it will become. A ridge across the
northeast Pacific will continue to build into the region along
with surface high pressure west of the PNW coast. This will keep
northwest flow aloft and northerly/northwesterly flow in place
at the surface through Tuesday. Highs will be a few degrees
warming today as the ridge strengthens and takes a stronger
hold on the region. Highs top are expected to top out in the mid
70s across the Willamette Valley. A thermal trough is expected
to develop this afternoon but models keep it confined to
southern Oregon through Thursday. Wednesday will be warmer with
highs peaking in the upper 70s and a 20-40% chance some
locations hit 80 around the Portland metro.

Going into Thursday, a series of disturbances across the Gulf of
Alaska round the top of the northeast Pacific ridge,
elongating/suppressing it farther south along the West Coast.
500 mb flow will become more zonal. Highs will fall back into
the mid 70s with a 40-70% chance of reaching 75 across the
Willamette Valley. Expect partly cloudy skies with some passing
high clouds during the day. -Batz

.LONG TERM...Thursday Night through Monday...WPC clusters show
good (80-90%) agreement that the ridge will be under some degree
of suppression or slight troughing by Friday. Only 20% of
members show weak troughing returning on Friday from Canada, but
even then precipitation looks minimal. On the flip side, only
about 10% of members show the ridge building further. In this
case, we would likely see a return of cooler temperatures if the
ridge breaks down by the end of the week.

Uncertainty in the upper level pattern over the Pacific
Northwest continues into the weekend, however, one thing the
clusters all have in common is a high pressure ridge over the
northeast Pacific Ocean. Most of the uncertainty relates to how
much of an influence this ridge has on our area. Clusters suggest
an ~70% chance of zonal flow or troughing and an ~30% chance of
ridging going into the weekend. Thus, NBM does show around a 8
to 10 degree spread between the 25th and 75th percentiles of
high temperatures over parts of the Willamette Valley for Friday
and Saturday. The spread on Sunday and Monday is a bit bigger
at 10-12 degrees, owing to a bit more uncertainty later in the
forecast period.

If models trend toward a troughing/zonal flow pattern, we`ll
likely see temperatures cool and potentially a slight chance
(15-24%) of PoPs. If models trend toward keeping the ridge,
then expect the forecast to maintain warmer, drier, and clearer
conditions. -Alviz/Batz

&&

.AVIATION...High pressure dominates, and generally VFR conditions
with clear skies are in place for most of Tuesday. Around 0500
Wed, some lower level stratus clouds move inland, bringing 80-90%
chance of MVFR cigs at coastal terminals. Slightly more cloud
cover is expected at northern areas (such as KAST); around a 60%
chance of IFR cigs can be expected during this time. Stratus
clouds burn off going into Wednesday morning, with 90% confidence
in return to VFR conditions by 20z Wed.

Winds will be northerly throughout the period, with somewhat
breezy/gusty winds at times throughout the rest of Tuesday
afternoon and evening. Coastal terminals could see gusts up to
25-30 kt up until around 08z Wed, after which winds will begin to
weaken. At all inland terminals, winds should peak around 20-25 kt
during this period. No LLWS expected. /JLiu

PDX AND APPROACHES...VFR with relatively clear skies throughout
most of the TAF period, other than some light high cloud cover.
Winds will become a bit gustier going into the evening, with gusts
up to 20kt possible beginning 22z Tue. These calm again going into
Wednesday morning, dropping to 5-10 kt around 07z Wed. /JLiu

&&

.MARINE...Typical summertime pattern of northerly winds as high
pressure builds through mid week. Winds are already increasing
with gusts currently around 25 kt. Recent models are bringing
gusts as high as 30 kt with isolated gusts to 35 kt this afternoon
with the peak wind speeds in PZZ253 and 273. Small Craft Advisory
remains on track.

In regards to seas, nothing overly remarkable as the
primary swell is from the northwest, and the wind wave from the
north. Wind waves will range from around 4 to 6 feet. Combined
seas will be 6 to 8 ft through Tuesday, though conditions ramp up
mid-week.
  -Muessle/JLiu

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 11 AM PDT Wednesday for PZZ251>253-
     271>273.
&&

$$

www.weather.gov/portland

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