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National Weather Service Area Forecast Discussion for Seaside, OR USA

fxus66 kpqr 191035

Area Forecast Discussion
National Weather Service Portland, OR or
235 am pst mon feb 19 2018 weather stays over the region for this week under
a northerly flow aloft. a few snow showers will linger over the
cascades today as an upper trough shifts slowly east over idaho. a
chance for light rain and snow tue and tue night as a couple of
shortwave troughs of low pres move south across the region. a couple
more shortwaves late in the week bring more chances for rain and
mountain snow.


.short through wednesday...a weak circulation center
was still evident in radar and satellite imagery moving south over
the north oregon cascasdes early this morning, on track to move
south of the forecast area by morning. the main focus for
precipitation potential then shifts to the shortave moving south off
the coast today, followed by another shortwave expected to track
south through western wa and or tue night. the main threat for
precipitation with the tue system will be to the coastal areas, with
just a slight chance of precipitation reaching east of the coast
range due to the track well offshore. better moisture is suggested
for the shortwave tue night for much of the area, mainly in the mid
levels. will bump up the pops for tue night for the interior more
into the range of 40 to 50 percent given good dynamics and adequate
moisture. as for temps today through tue night, air mass will be
rather cold, as 850 mb temps still expected to bottom out in the
range of -10 to -12c this morning, modifying slightly tue and tue
night to -6 to -10c. temps likely to struggle to break out of the
30s anywhere both today and tue. this suggests snow levels to lift
only to 500 to 1500 ft above sea level on the coast tue afternoon,
and only a few hundred feet above inland valley floors. tue night
expect precipitation to be mainly snow except mixed with rain on the
coast and at lowest elevations inland.

the tue night shortwave winds up reinforcing the cold air over the
region, with 850 mb temps remaining in the range of -7 to -10c,
again suggesting surface temps struggling to top much more than 40f
despite a drier air mass and likely some sunshine. the only
remaining chances for snow showers will be limited to the cascades.

.long changes. previous discussion follows...wednesday
night through sunday...the large-scale pattern remains rather
consistent across the western u.s. for the second half of this week,
as a high amplitude ridge remains over the pacific centered
near/around 140w with a deep trough in place over the western conus.
this will maintain generally northerly flow over the region, with a
series of shortwave impulses  moving through the region. these
impulses will be focus points for additional chances of rain/snow
through the week. forecast models continue to display somewhat
different scenarios with various disturbances moving near or through
the region and as such, confidence in the details (specifically,
precipitation) remains somewhat lower than normal through the long
term forecast period. maintained some mention of pops late wednesday
and thursday, but at this point expect the snow level to remain
around 1,500 feet or so through this time period.  while the ecmwf
has some additional moisture compared with the gfs, at least half of
the gefs members are more favorable for precipitation so have trended
this way. the next strong system could arrive around the weekend and
depending on the degree of cold air, there will be some potential for
snow down to the higher hills once again, depending on how much cold
air is in space. nonetheless, below normal temperatures and only
occasional infusion of moisture can be expected through the week.


.aviation...surface low from last evening dissipated. currently a
trough setting up along a kast-keug to willamette pass line in
response to increasing high pressure over western wa and nw or.
lingering mid-level moisture giving cigs around 4000-6000 ft
across the area. but lower cigs 1500-2500 ft for the interior,
mainly south of kpdx. overall conditions drying today as
northerly offshore strengthens. however expect mvfr cigs to
linger ksle to keug area through at least mid-morning.

pdx and approaches...vfr prevailing with cigs around 5000 ft this
morning then gradual clearing through the day. temperatures to
warm above freezing around 20z mon. /mh


.marine...wind speeds continue to slowly ease this morning. only
the outer zones pzz270 & 275 remain above 25 kt. have dropped the
gale warning for pzz275, but models indicate gusts to 35 kt may
be occurring in the extreme sw part of the zones. winds will ease
through the day then should be backing to the s-sw late tonight
and tue. models are in better agreement that a low will approach
the waters on tue. but the tracks are quite different. the gfs &
nam take the low on a se track remaining offshore. ecmwf takes a
different track by moving the low across the waters and ashore
over nw or. at best may see 20 to 25 kt with this system.

models show another low pressure system moving north to south
near the waters late wed into thu, but there are major
differences between the models as to the impacts of the low due
to strength and track.

seas continue to slowly moderate with 15 to 17 ft over pzz270 &
250 and up to 23 ft at the waldport offshore buoy (46098.) seas
continue to fall today, dropping below 10 ft by mon evening.


.pqr watches/warnings/advisories...
pz...small craft advisory for winds until noon pst today for waters
     from cape shoalwater wa to florence or from 10 to 60 nm.

     small craft advisory for hazardous seas until 10 pm pst this
     evening for coastal waters from cape shoalwater wa to
     florence or out 60 nm.

     small craft advisory for rough columbia river bar until 7 pm
     pst this evening.

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

Information courtesy of the National Weather Service - NWS Portland...
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