903
FXUS66 KPQR 230144 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
644 PM PDT Sat Jun 22 2024

.SYNOPSIS...Cooler temperatures will return Sunday into Monday
as onshore flow strengthens, along with some light
rain/aggressive drizzle tonight into Sunday morning for the
Coast Range and Cascades. Warm and dry conditions return
Tuesday. Precip chances become more widespread Wednesday into
Thursday as a more robust upper level trough moves inland, which
will also bring the return of cooler temperatures.

&&

.SHORT TERM...Now through Tuesday Night...The upper level ridge
which has been the dominant synoptic feature the past few days,
will continue to break down tonight as the a broad upper level
trough from Hadia Gwaii pushes eastward through Sunday. High
resolution models are showing a cold front that is associated
with the upper level trough will bring near normal daytime high
temperatures to the region on Sunday. Daytime highs in the upper
60s to low 70s for inland locations, upper 50s to mid 60s for
the Cascades and low to mid 60s for the coast. In addition to
the cooler temperatures, areas along the Coast, Coast Range and
Cascades could see some very light rain/aggressive drizzle
starting later tonight and continuing through Sunday afternoon.
While the cooler temps and moister conditions may be welcomed,
do not expect any amount of significant rainfall accumulation
with this front. In fact, most locations will likely not see any
precipitation.

After this broad trough has pushed eastward late
Sunday, the region develops a zonal flow pattern, which will
signal the start of another warming trend for the middle part of
the week. Currently, daytime highs are expect to warm into the
mid to mid 70s inland, upper 60s to low 70s for the Cascades and
upper 50s to mid 60s along the coast. Tuesday, the warming
trend will continue as a Great Basin high will stretch
northward, resulting in 850 mb temperatures reaching toward 11C
to 15C which means that daytime highs will likely warm once
again. Overall, expect warm and dry conditions to persist
through the middle of the upcoming week. -42


.LONG TERM...Wednesday through Saturday...Wednesday continues
to see the trailing end of the ridge as it moves out, with a 75%
chance of temperatures above 75 degrees. The next shortwave
begins to move in late Wednesday which could bring some light
rain as the next shortwave trough begins to move in. There is
around a 20% chance of 24hr rainfall (Wed 5am - Thu 5am) above
0.10" at the WA coast, WA Coast Range, and WA Cascades. At
inland/lowland areas, chance is lower than 5%. WPC Cluster
analysis shows an 85% chance of a shortwave trough fully moving
in on Thursday, with slightly stronger rain accumulations
expected, as well as cooler temperatures. Temperatures will be
in the low 70s, with only a 25% chance of temperatures over 75
degrees. Precipitation is skewing weaker than previous
forecasts, with around a 30-40% chance of 24hr accumulation (Thu
5am - Fri 5am) at the coast, Coast Range, and Cascades above
0.10". This drops to 10% in the Willamette Valley, under 5%
south of Salem.

Friday is expected to see similar conditions, and Saturday sees
70% ensemble agreement in a return to zonal flow, with possibly
some insubstantial drizzle.-JLiu

&&

.AVIATION...Skies cleared more than expected along the coast
today, and as of 2130z skies along the coast were mostly clear
KTMK southward. North of KTMK, clouds are increasing with VFR cigs
generally between 040-050. A weak cold front will cause clouds to
continue to thicken and spread southward along the coast this
afternoon and evening, with hi-res probabilistic guidance
suggesting over an 80% chance of MVFR cigs for the entire S WA/N
OR coast by 23/02z. Areas of coastal drizzle will likely push
cigs/vsbys into the IFR category for some coastal locations
between 23/00z-06z.

The cold front will also lead to a strong onshore push this
evening with gusts 20-25 kt likely through gaps in the Coast
Range. Eventually this will cause stratus to develop along the
Cascade foothills then backbuild into the Willamette Valley, with
increasing chances of MVFR later in the evening. By 08z, latest
high-res forecast models suggest greater than a 70-80% chance of
MVFR cigs for the Willamette Valley terminals east of I-5 (i.e
KPDX, KTTD, KSLE, KUAO, etc). Suspect this is about accurate for
cigs in general, but cig heights may end up just above 030 for
some of this area. With onshore flow persisting into Sunday and
the moist layer considerably deeper than today, clouds should
linger well into the day. Isolated showers are not out of the
question over the Coast Range and Cascades Sunday.  -Weagle

PDX AND APPROACHES...VFR with mainly clear skies and light onshore
flow today. W-NW winds will increase considerably after 22/23z-24z,
with sustained winds 10-15 kt and gusts up to 25 kt between
23/00z-08z. Winds will gradually decrease thereafter. Backbuilding
stratus from the Cascade foothills will lead to a 70-80% chance
of cigs by 23/10z, but chances of MVFR are closer to 50%. Cigs
that develop will persist well into the day Sunday.-Weagle

&&

.MARINE...
Low pressure near 1000 mb was approaching Haida Gwaii
Sat morning, pushing a weak cold front across the Pac NW coastal
waters later today. Trajectory of low pressure does suggest a weak
dynamic fetch which could push seas up close to 10 ft Sunday
afternoon and evening. That said, the odds of seas reaching 10 ft
are too low (20-30%) to warrant a Small Craft Advisory at this
time. Otherwise, high pressure will expand across the waters
Sunday and Monday while thermal low pressure strengthens over the
Sacramento Valley and near the OR/CA border. This will lead to
moderate N-NW flow early next week, with about a 30-40% chance of
wind gusts exceeding SCA criteria of 21 kt Monday afternoon.
-Weagle

&&

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

$$

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