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

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Area Forecast Discussion
National Weather Service Portland, OR or
252 am pdt tue may 17 2022

.synopsis...southwesterly flow aloft and surface high pressure
will bring seasonal conditions today. the next weather system
reaches the coast late this evening and moves inland wednesday. the
result will be a return to a cooler and wetter pattern. snow levels
lower to just below the cascade passes wednesday night. the yo-yo
pattern continues friday and saturday with warmer and drier
conditions. chances for rain increase again late in the weekend into
early next week.

&&

.short term...(today through thursday)...satellite reveals broad
southwesterly flow aloft over the ne pacific with a developing
shortwave near 47n 131w.  but for today will see increasing high
clouds from this system while remnants of clouds back building from
the cascades across the valley dissipates. the aforementioned
shortwave will bring rain to the north coast later this evening then
spread south and east overnight.  models are in decent agreement in
timing of rain with the latest hrrr notably slower.  wednesday will
be a rather damp day with about a 0.1 to 0.25 inch in the valley,
0.25 to 0.35 inch at the coast and coast range, and 0.5 to 0.75 inch
in the cascades. snow levels will be well above the cascade passes
wednesday morning, but lower 3000 to 3500 feet by late wednesday
night as another, cooler system slides into the region from the gulf
of alaska.  models generally maintain the upper 500 mb pattern as a
open trough as it slides southeast across the region towards the
great basin later thursday. a strong jet stream accompanies this
trough with the core of the jet over the northern part of the cwa.
thunderstorm (12-hr) chances per nbm remain in the 15-25 percent
chance thursday. however, model soundings show some thin cape
thursday afternoon, but there is a capping inversion above the -10c
level, which would limit potential for lightning. so for now have
chose not to include thunderstorms in the forecast.

.long term...(thursday night through monday)...the broad and
expansive upper level trough migrates east thursday night and friday
to the great basin.   however, there are model differences regarding
how fast this occurs.  ncep cluster analysis bears this out with
various clusters show differences in the strength and position of
ridge building over the northeast pacific into the pacnw.  friday and
saturday look mainly dry, though friday may end up with higher
chances for showers, mainly over the mountains.  nbm increases pops
on sunday and this looks reasonable with a weakening upper ridge and
increasing southwest flow over the region.  in a nutshell, kept close
to nbm output for sunday and monday, but with some of the uncertainty
in the model analysis the forecast may trend drier for late in the
weekend. /mh

&&

.aviation...upcoming 12z tafs: stable air mass across region, with
westerly flow aloft and with light low-level onshore flow. do
have mid-deck clouds (5000 to 7000 ft msl) persisting over the
cascades, and to west a bit over parts of the willamette valley
early this am. this deck will gradually dissipate this am.

elsewhere, still expecting pockets of low end mvfr cigs along the
coast into the coast range valleys, as well as into parts of sw
washington such as the cowlitz valley. these clouds too will break
up and thin out by 18z.

otherwise, vfr today with increasing high clouds. this as front
well offshore approaches. as front draws bit closer, will have
clouds thickening, with increasing mid-level clouds after 00z.

for detailed regional pac nw aviation weather information, go
online to: https://weather.gov/zse

kpdx and approaches...vfr this am, with scattered to broken 6000
ft deck very slowly dissipating. otherwise, vfr today with
variable high clouds. increasing mid-level clouds after 00z.
/rockey

&&

.marine...transition weather today, with high pres over the
coastal waters. this high will shift inland tonight, as a
moderately strong front approaches from the west. this front
should hold together long enough, that with decent gradients,
should pop southerly winds of 20 to 30 kt on the northern waters
later tonight. gusts 30 to 35 kt likely. so, will upgrade gale
watch to a gale warning for later tonight through wed am. winds
not as strong to the south, but enough to warrant small craft
advisory, with gusts up to 30 kt at times.

front will push onshore mid to late wed morning, with winds
becoming more west to southwesterly, and easing. but, do have bit
more swell arriving, with 9 to 11 ft swell for wed. as such, will
likely need to maintain small craft advisory for winds/seas for
wed afternoon through wed night.

models are coming into agreement high pressure should return to
the northeast pacific late this week. this should bring a quieter
stretch of weather and allow seas to subside back below 5 ft
towards friday and into the coming weekend.

&&

.pqr watches/warnings/advisories...
or...none.
wa...none.
pz...small craft advisory until 8 am pdt this morning for columbia
     river bar.

     gale warning from midnight tonight to 11 am pdt wednesday for
     coastal waters from cape shoalwater wa to cascade head or
     out 60 nm.

     small craft advisory from midnight tonight to 11 am pdt
     wednesday for coastal waters from cascade head or to
     florence or out 60 nm.

&&

$$

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