656
FXUS66 KPQR 201643 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
943 AM PDT Thu Jun 20 2024

Aviation Discussion Updated...

.SYNOPSIS...Much warmer through the remainder of the week under
building high pressure, with moderate heat risk expected from
Portland to Salem Thursday through Saturday. More seasonable
temperatures return Sunday into early next week. Conditions will
remain dry over the next week aside from areas of coastal drizzle
Saturday night/Sunday morning.

&&

.DISCUSSION...Thursday through Tuesday night...High pressure
dominants the weather pattern over the next several days, bringing
mostly sunny skies with hot afternoon temperatures inland. Heat risk
remains in the moderate category from Portland to Salem Thursday
through Saturday with high temps in the upper 80s to lower 90s.
Confidence is high in regards to the temperature forecast as very
little model spread is evident; the NBM 1D Viewer highlights this
well as the 10th-90th percentile only ranges from 89-93F on Thursday
and 87-94F on Friday in the Portland metro. While high temps in the
lower 90s in mid to late June isn`t quite enough to warrant a Heat
Advisory, those extremely sensitive to heat could suffer from heat
exhaustion or heat stroke if exposed to the heat for long enough,
especially in direct sunlight. Be sure to stay hydrated and for those
who must work outside, plan on frequent breaks during the afternoon
hours. Much cooler at the coast where low-level onshore flow will
keep high temps in the upper 60s to lower 70s. -TK

Confidence is high for a period of relatively cooler temperatures
across all of northwest OR and western WA Sunday into early next week
as onshore flow strengthens over the area, however models and their
ensembles show a fair amount of model spread regarding temps. The
coolest model guidance suggests high temps around 70F over inland
valleys, while the warmest guidance suggests highs in the lower 80s.
The outcome will be highly dependent on the degree of morning cloud
cover. Nevertheless, it will most definitely be cooler compared to
the next few days.

Despite the cooler temps, conditions look to remain dry through early
next week across the area. The only exception to that is at the coast
Saturday night/Sunday morning when a period of drizzle or light rain
is possible from Lincoln City northward with a passing shortwave
trough. This shortwave trough will deepen the marine layer to around
1-1.5 km according to NAM/GFS soundings, which is more than deep
enough to produce drizzle given the weak lift in place. Nearly every
ensemble members from the GEFS/EPS/CMC shows light QPF amounts in
Astoria. In fact, some members from the CMC show upwards of 0.1
inches of rain. The current forecast mentions areas of drizzle, which
seems reasonable for now.  -TK

&&

.AVIATION...Upper level troughing over the region this morning
with light west-northwesterly flow aloft. Surface high pressure
remains over the region with dry conditions. This will maintain
VFR with variable high clouds at times. Only exception is at the
coast, where onshore flow will maintain areas of IFR stratus
through this morning, improving to VFR around 19-21Z Thursday.
Expect gradual clearing working its way southward along the coast
later this morning, by 18-19Z at KAST. There is around a 60-70%
chance that conditions improve to MVFR or VFR at KONP this
afternoon.

PDX AND APPROACHES...VFR with mostly clear skies throughout the
TAF period. Northwest winds increasing to around 8-10 kt this
afternoon.
-JH

&&

.MARINE...Not much change as high pressure offshore is expected
to persist through the week. Northerly winds around 15-20 kt will
continue today, strongest offshore beyond 10 NM. Expect periods
of winds gusting up to 25 kt through Friday during the late
afternoon and evenings. Will maintain the Small Craft Advisory for
the outer coastal waters through this evening. Will likely need
another advisory on Friday. Seas around 4 to 6 feet will
generally be wind driven through the week. A weak front is
expected to approach the coastal waters this weekend, weakening
the high pressure. Winds will likely become more onshore and ease
to below 15 kt. The front will also bring an increasing westerly
swell, though seas are only likely to build up to 8 ft on Sunday.
/DH


&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 8 PM PDT this evening for PZZ271>273.

&&

$$

www.weather.gov/portland

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