Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 241811

Area Forecast Discussion
National Weather Service Portland OR
1010 AM PST Fri Nov 24 2017

.SYNOPSIS...A series of fronts will continue periods of wet weather
into next week. Snow levels will be near the Cascade passes
but with light precipitation and minimal snow accumulations at pass
levels. Showers diminish for today and tonight, but rain returns
under a weak warm front Saturday afternoon and night. A cold
front crosses Sunday bringing a better chance for snow at the
passes Sunday and Monday.


.SHORT TERM...Today through Sunday...Showers will continue into early
this afternoon mainly across SW Washington and extreme NW Oregon.
Areas south of Salem will be mostly dry today, although can not rule
out the possibility oa a stray shower or two. Temperatures will be
much cooler today with most weather stations in the region  reporting
hourly temperatures 7 to 14 degree less than 24 hours ago. snow
levels are around 4500 feet this morning. Tonight will be dry and
cool with possibly patchy fog in the interior valleys. ~TJ

Rest of the discussion is from the previous issuance (251 AM)...A
stronger upper shortwave will approach from the southwest on Sat.
The associated surface low will deepen to around 985 mb Sat afternoon
as it tracks north along 130W off the north Oregon coast. A warm
front will brush the area with rain Sat afternoon and should be north
of the area Sat night. The CWA will be in the warm sector ahead of
the cold front for relatively mild Sat evening. The cold front will
spread rain to the coast Sat evening and inland late Sat night. It
will move across the area Sun morning. Snow levels remain above pass
levels crossing the Cascades, then lower closer late Sun afternoon
for some light accumulations.

There is a chance for a burst of gusty winds along the coast and
coastal mountains as the low moves north along the coast Saturday
evening.   /mh

.LONG TERM...No Changes. Previous discussion follows...Sunday night
through Thursday... A colder upper level trough will support snow
levels staying near the Cascade passes with showers over the region
Sunday night and Monday. The models vary on how quickly the upper
trough will move east, but generally agree that an upper ridge will
replace the upper trough Monday night. As Monday`s upper trough
advances into the Great Basin and Plains, models remain in reasonable
agreement and suggest rising heights across the Pacific Northwest
into Tuesday. This may bring a bit of a break in the precipitation,
though there is some hint that the northern extent of the forecast
area (primarily north of a Tillamook to Mt. Hood line) may be clipped
by a front associated with a low moving into central B.C. As a
result, have lowered PoPs across the southern and southeastern
portions of the forecast area. Models then diverge more significantly
as we move into the second half of next week, so have held the
forecast closer to climatological normals.


.AVIATION...Still some pockets of MVFR/IFR cigs for the next
couple hours, but conditions should be all VFR by 20-21Z. Stable
southwest flow aloft mean decreasing mid-level clouds this
afternoon, but our next system will start to bring in high level
clouds this evening. Increasing easterly wind from the Columbia
Gorge and light easterly winds along the coast tonight should
keep the north Willamette Valley and coastal terminals VFR
overnight tonight, but less wind and stable conditions down at
SLE and EUG mean a good chance of fog developing at these sites
after 06-08Z.

KPDX AND APPROACHES...Seeing some sct015 that could briefly go
broken, but that should clear out by 19-20Z. Otherwise, generally
VFR today and tonight. East winds developing around 06Z tonight.


.MARINE...No changes. Previous discussion follows...
More benign weather on the coastal waters today into Saturday.
High pres remains well inland, with lower pres well offshore.
This will maintain south to southwesterly winds on the waters
today, with 10 to 20 kt. But, enough gradient over the outer
waters that will see gusts up to 25 kt at times. Will expand
Small Craft Advisory for winds to cover all outer waters for
today through Sat am. Seas mostly 7 to 9 ft, but with bit more
wind over the outer waters, seas will range from 9 to 11 ft over
the outer north waters. Will maintain Small Craft Advisory for
that area through Sat.

Low pres will approach the region from the sw on Sat. This will
turn winds more southeasterly. Models continue to show the low
staying well to west of the region as it moves north towards
west tip of Vancouver Island Sat night. But, cold front will
swing east across the coastal waters Sat night into Sun am. Winds
will increase, but generally stay southeasterly until just ahead
of the front, then will turn hard south. Reasonable confidence
that will have solid southerly gales, with strongest winds
between midnight and 6 am Sun. Gale watch remains in effect for
Sat afternoon through Sun on the outer waters, but will likely
include the inner waters later Sat night as front draws closer.
Seas will build Sat night, with 15 to 22 ft on the outer waters
with the stronger winds, and 14 to 17 ft on the inner waters.

Another weaker system looks pass south of the region on Mon.
Then looks more tranquil over the region as high pres builds over
the region. If current trends continue, could see northerly
winds 10 to 15 kt for good part of next week.


PZ...Gale Watch from Saturday afternoon through late Saturday night
     for Waters from Cape Shoalwater WA to Florence OR from 10
     to 60 NM.

     Small Craft Advisory for winds until 1 PM PST Saturday for
     Waters from Cape Shoalwater WA to Florence OR from 10 to
     60 NM.

     Small Craft Advisory for hazardous seas until 1 PM PST Saturday
     for Waters from Cape Shoalwater WA to Cascade Head OR from
     10 to 60 NM.


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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. is the U.S. government's official web portal to all federal, state and local government web resources and services.