National Weather Service Area Forecast Discussion for Long Beach, WA USA

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fxus66 kpqr 110511 aaa
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Area Forecast Discussion
National Weather Service Portland, OR or
911 pm pst tue dec 10 2024

updated aviation discussion

.synopsis...high pressure weakens over the region as the next
offshore system slowly approaches. this system will bring a round of
light rain wednesday afternoon into thursday. rain dwindles later
thursday but a stronger system arrives friday for more rain, and
breezy conditions especially at the coast and through the gorge.

.short term...tonight through friday...fog has lifted for the most
part but stratus remains over much of the willamette valley and
portions of the southwest wa interior. but with offshore flow through
the gorge (gusting 35 kt at kttd) the portland/vancouver metro area
has cleared out of the stratus. with not much wind elsewhere and a
strong surface inversion, not expecting much clearing of the stratus
this evening. will likely see fog redevelop, but maybe late tonight
and wed morning will see the clouds break up as the next upper
trough approaches. this system to bring light rain to the area wed
afternoon into thu with most of the rain falling at night. qpf
amounts are modest over our area as the main part of the system
heads south. a stronger system moves to the area fri for more rain.
deterministic models not in great agreement on the strength & track
of this system. gfs has a 969 mb surface low off the wa coast fri
evening while ecmwf has a 984 mb low off the north oregon coast.
this will result in breezy southeast to east winds at the coast as
well as the gorge & east portland/vancouver metro area. snow levels
remain above about 2500-3000 ft through both systems, though dip to
500-1000 ft eastern gorge zones with the thu system. snow amounts
look rather modest as well with no winter weather headlines expected.

.long term...saturday through tuesday...the overall theme is
progression of two upper troughs over the weekend into early next
week. one trough moves east across the region saturday. after that
deterministic model solutions diverge with the gfs being a little
more progressive and ecmwf a little slower. cluster analysis is a bit
"messy" over the weekend into early next week showing varying amounts
troughing over the pacnw. but by day 7 (tue), the clusters are in
decent agreement with varying amounts of ridging over the pacnw.
in summary it`ll be rather unsettled through mon, with potential for
a dry period beginning tue.

&&

.aviation...upper level ridge of high pressure over the region
will continue to weaken overnight while flow aloft becomes more
southerly. mid to high level clouds will stream across the area
ahead of an upper level disturbance through wednesday morning. a
strong subsidence inversion is expected to maintain lifr stratus
across the southern and central willamette valley between kuao and
keug. there is more uncertainty with fog development, but do
expect some reduction to visibilities through 18z wednesday.
guidance suggests better than 80% chance that conditions improve
to vfr after 20z wed. coastal terminals remain vfr through the
taf period as offshore flow persists. breezy east winds persist
through the columbia river gorge, with gusts up to 30 kt in the
eastern portland metro. a frontal system will approach the area by
wednesday afternoon with rain spreading inland around 00z thu.

pdx and approaches...predominately vfr through the taf period
with mid to high clouds ahead of a system. low chances (10%) of
lifr stratus or fog developing between 16-19z wed morning. rain
chances increase after 00z thu along with lowering cigs, but
expected to remain vfr. southeast winds expected around 5-10 kt.
/dh

&&

.marine...late tonight into early wednesday morning, winds turn
southerly ahead of an approaching frontal system. expect southerly
to southeasterly wind gusts up to 25 kt across the waters tonight
through late wednesday night. therefore, a small craft advisory
has been issued for all of the waters including the columbia river
bar through 4 am pst thursday. seas remain around 8-9 feet at 15
seconds as this system pushes through, but will gradually build
to 11-13 feet at 15 seconds on thursday as a westerly swell
follows this system.

another low pressure system will continue active weather toward
the end of the week, with increasing confidence for another round
of gusty winds and building seas. the most impactful time frame
is currently forecast between early friday morning to early
saturday morning. guidance suggests a 70-80% chance of gale force
wind gusts and a 60-70% chance of seas exceeding 15 feet by
saturday.      -alviz

&&

.pqr watches/warnings/advisories...

or...none.
wa...none.
pz...small craft advisory from 4 am wednesday to 4 am pst thursday
     for pzz210-251>253.

     small craft advisory until 4 am pst thursday for pzz271>273.
&&

$$

www.weather.gov/portland

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