Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 201747 CCA

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1046 AM PDT Fri Apr 20 2018

Updated Aviation and Marine Discussions.

.SYNOPSIS...Dry and mild weather today before a cold front spreads
light rain and Cascade snow across the region late tonight. Some
showers may linger over the Cascades Saturday morning, but otherwise
the day will be dry, but cool. Dry weather continues Sunday into next
week. Temperatures are expected to warm into the 70s Monday and
Tuesday as a thermal trough settles over NW Oregon and offshore flow


.SHORT TERM...Today through Monday. Dry and mild weather continues
today with increasing high clouds ahead of an approaching front. A
warm front brushes by to the north this afternoon with little impact
to the weather.  The cold front will produce light rain along the
coast this evening moving inland late tonight. Snow levels will be
around 4500 feet for the south Washington Cascades and 6000 feet for
the Cascades of Lane County when the precipitation arrives tonight.
He snow levels then lower to 3500-4500 feet Saturday morning as light
showers linger over the Cascades. The highest forecast rainfall
amounts this afternoon through Saturday afternoon are around 0.20
along the north coast, the Willapa Hills, and the south
Washington Cascades. The Willamette Valley, especially south of
Salem, are not expected to see much rain (0.01-0.05 inch). THe
Cascades can expect a few inches of new snow with no expected impacts
for the Cascade passes.

A few showers will linger over the the Cascades and across extreme SW
Washington Saturday morning, but most areas west of the Cascades will
remain dry. Cool and cloudy conditions with onshore flow is  expected
Saturday in the wake of a cold front. Dry weather continues Sunday
with surface high pressure building over the area. A shortwave upper
trough may keep some clouds around and somewhat limit heating, but
the afternoon temperatures will still peak slightly above the
seasonal normals.

A sharp upper ridge moves over the Pacific NW Sunday night and Monday
continuing dry weather. A thermal trough develops along the coast
Sunday night and persists Monday for offshore flow and warmer
temperatures. Much of the area will warm into the 70s Monday
afternoon with the coast likely peaking in the upper 60s.~TJ

.LONG TERM...No Changes. Previous discussion follows...Monday night
through Thursday...Models have come into better agreement regarding
the weather next week, now showing continuing high pressure and dry,
warm conditions. Even the 12Z GFS is on board with continued warming
Tuesday and Wednesday with MEX guidance showing temperatures as warm
as the upper 70s in the valley on Wednesday. Haven`t gone that warm
with the forecast, but do have 70s inland Monday through at least

Where the models do still diverge is with the track of an upper low
pressure system which moves south off the west coast through midweek.
After that, the GFS continues to spin the low well off the California
coast through the end of the week while the ECMWF brings the low into
southern California. Any shower or thunderstorm chances in the
Cascades next week will depend on the exact track of the low, but
have kept mentionable chances out of the forecast for now. This means
that after Saturday evening, there are currently no mentionable rain
chances anywhere in the local forecast area through the rest of the
7-day forecast. Vampires beware. Here comes the sun.


.AVIATION...Expect VFR conditions to persist through this evening
along the coast and through tonight in the interior. Mid and high
clouds look to increase through the day ahead of an approaching
cold front. This front will bring light rain and MVFR cigs to
coastal TAF sites later this evening. Light rain will spread
inland overnight and could bring brief periods of MVFR cigs to
interior TAF sites late tonight/early Sat morning. Conditions
across the forecast area look to improve towards VFR Sat
morning, with clouds clearing through Sat afternoon/evening.

KPDX AND APPROACHES...VFR continues through tonight under
increasing mid and high clouds. Light rain, with occasional MVFR
cigs, look to impact the terminal after midnight tonight. Expect
conditions to improve Sat morning behind the front, with clouds
clearing Sat afternoon/evening. /64


.MARINE...A front moving eastward across the waters tonight will
bring Small Craft Advisory level wind gusts of 25 to 30 kt to the
waters. Expect the strongest winds across the northern waters.
Seas will climb into the 9 to 12 ft range by early Saturday
before subsiding Saturday afternoon.

Thermal low pressure over northern California will build
northward along the Oregon coast over the weekend. This will
bring a summer-like northerly wind pattern developing over the
weekend. Winds may turn offshore for a day or two early next week
with gusty winds of 20 to 25 kt possible across the waters
adjacent to the coastal gaps. Surface high pressure looks to
return to the northeast Pacific towards the middle of next week,
which should keep winds light and seas under 10 ft. /Neuman


PZ...Small Craft Advisory for winds from 6 PM this evening to 11 AM
     PDT Saturday for Coastal Waters from Cape Shoalwater WA to
     Cascade Head OR out 60 NM.

     Small Craft Advisory for hazardous seas from midnight tonight
     to 9 PM PDT Saturday for Coastal Waters from Cape
     Shoalwater WA to Cascade Head OR out 60 NM.

     Small Craft Advisory for winds from 8 PM this evening to 9 AM
     PDT Saturday for Coastal Waters from Cascade Head OR to
     Florence OR out 60 NM.

     Small Craft Advisory for hazardous seas from midnight tonight
     to 3 PM PDT Saturday for Coastal Waters from Cascade Head
     OR to Florence OR out 60 NM.

     Small Craft Advisory for Rough Columbia River Bar from 7 PM to
     11 PM PDT this evening.

     Small Craft Advisory for Rough Columbia River Bar from 5 AM to
     2 PM PDT Saturday.



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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.