086
FXUS66 KPQR 222144
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
242 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...Tonight 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 will
be a 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 by
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 be in the low to mid 80s inland, upper 60s to mid
70s for the Cascades and low to upper 60s along the coast. Overall,
expect warm and dry conditions to persist through the middle of the
upcoming week. While relatively cooler periods are expected, they
will be short-lived for the Pac NW. /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 evening hours look to see some
light rain as the next shortwave trough begins to move in, but
precipitation looks weak, with 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

&&

.BEACH HAZARDS...Low pressure approaching Haida Gwaii this morning
appears to be taking a track which supports a weak dynamic fetch to
build swell and aim it toward the Pac NW coast. This swell will
spread across the coastal waters Sunday, especially Sunday afternoon
and evening. Given the warm weather inland this weekend which will
likely lure people toward the beaches, have some concern for the
increased risk of sneaker waves Sunday. Will highlight this on social
media, but this is a marginal case so we will likely refrain from
issuing a Beach Hazards Statement for this event.  Weagle

&&

.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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