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

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Area Forecast Discussion
National Weather Service Portland, OR
252 pm pst thu mar 11 2010

.synopsis...the next frontal system will impact the forecast area
through friday. a warm frontal part has stalled over nw oregon today.
a secondary wave will reinforce the frontal zone tonight. the cold
front finally moves inland friday. this system will bring significant
rainfall to the coast and coast range. after the upper trough moves
through friday night...a warm front will brush the area saturday.
high pressure takes over sunday through early next week.

&&

.short term...a moist baroclinic zone stalled spreading precipitation
across the area today with the main focus over the north and central
zones. the long moisture fetch leading into the areas extends all
the way back beyond 170w. amsu satellite total precipitable water
estimates still indicating 0.75 to 1.00 inches moisture with this
fetch. also amsu rain rates are around 0.06 to 0.10 inch per hour.
orographics will weaken this evening as mid level winds back and
decrease as a developing wave on the front now near 40n/140w
approaches the coast later tonight. but as this wave nears the area
precipitation will increase...so will probably see a good response
in the coastal rivers and some of the willamette tributaries later
fri and fri night.

with regard to the high wind potential on the coast...models have
backed off on strength of the winds since yesterday runs. 850 mb winds
are down to 60 knots for the central coast and even less for the
north coast zones.  so have ended high wind watch for the south
washington and north oregon coast zones but upgraded to a warning
for the central coast zones for late tonight and fri morning. winds
inland should pickup as well during the morning as the front shifts
inland and cold air advection arrives for gusty conditions.

snow levels will be fairly high tonight and early fri...but will come
crashing down fri afternoon. however model qpf and 850 mb orographic
component not all that favorable for snow advisory amounts. the upper
trough moves through later fri night with decreasing showers sat as
the moist low level air mass stabilizes.

.long term...reasonably good agreement amongst guidance for late this
weekend through mon...showing a ridge holding in over the interior
pac nw...with a deep trough progressing slowly from 150w to 140w.
with a baroclinic zone offshore through mon...so will go a with
predominantly dry and mild forecast sun and mon. general trend for
tue on shows a shortwave and cold front lifting ne and pushing
inland...but timing becomes an issue with gfs the most progressive
with the system. given the developing model discrepancies...will
trend forecast toward climatology after tue.

&&

.aviation...flying conditions varying considerably this afternoon as
frontal system remains stalled over nw oregon. prevailing conditions
expected to remain vfr through the evening...although areas of cigs
and visibilities down into ifr range and occasionally up into vfr
category will persist. modest general improvement into vfr category
expected later tonight as front lifts n...but pockets of mvfr
conditions expected to remain overnight.

kpdx and approaches...prevailing mvfr conditions expected to
continue into the evening before returning to vfr later tonight.
however...areas of lower conditions are likely to persist...
especially in upslope areas to the n and e of kpdx.
&&

.marine...winds will rise again overnight...reaching gale force
again early fri morning as cold front pushes across the waters.
winds will be slow to drop off behind the front fri as a surface low
trailing the front moves through the wa coastal waters fri night.

a westerly swell train with relatively long periods in excess of 15
seconds continues to push ashore this afternoon. biggest seas are
over the northern waters...with buoy 46089 up to 25 ft at 21z. this
swell expected to slowly diminish through the teens of ft over the
next couple of days. locally generated southerly short period waves
will accompany the front fri creating a more chaotic sea.
&&

.pqr watches/warnings/advisories...
wa/or...high surf advisory north and central oregon coast and s
     wa coast until midnight.

     winter weather advisory south washington cascades through
     8 pm tonight.

     high wind warning central oregon coast midnight tonight
     through 10 am fri.

pz...small craft advisories for wind and hazardous seas cape
     shoalwater florence until midnight.

     gale warning cape shoalwater florence midnight tonight to noon
     fri.

     small craft advisory for rough columbia river bar tonight and
     fri.

&&

$$

more weather information online at...
http://weather.gov/portland

this discussion is for northwest oregon and southwest washington from
the cascade crest to 60 nautical miles offshore. the area is commonly
referred to as the forecast area.