-- Discussion containing changed information from previous version are highlighted. --
000
FXUS66 KPQR 250420 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
919 PM PDT Sun Mar 24 2019

Updated Aviation and Marine sections

.SYNOPSIS...High pressure briefly brings dry and mild weather today
across southwest Washington and northwest Oregon. Weather turns
cooler and wetter starting Monday as an upper-level trough settles
over the northeastern Pacific and Pacific Northwest.

&&

.SHORT TERM...Today through Wednesday...A shortwave ridge is passing
over the area today, causing this clear sunny weather this
afternoon, as well as the morning fog this morning. This will be
short lived, however. A broad unstable air mass off the West Coast
can be seen on satellite, and this is the broad upper-level trough
that will be settling itself off the coast of Washington and Oregon
through most of this week.

This negatively tilted trough will bring the first shortwave up from
the southwest late tonight into Monday. This means rain and some
mountain snow at higher elevations. The warm front lifts north,
spreading rain across the area Monday morning, with stratiform rain
turning to showers behind the warm front as the unstable air mass
moves into northwest Oregon and southwest Washington. Expect showers
to stat to taper off Monday night, but won`t completely clear out on
Tuesday. Any showers on Tuesday should stay confined mainly to the
Coast and Coast Range. Offshore flow increases late Tuesday night
into Wednesday as the low pressure center associated with the base of
this upper-level trough moves closer to southwest Oregon and starts
to approach from the southwest. Wednesday should stay mostly dry as
the low stays south of our area, but Lane County may get clipped by
some precipitation on the north side of the low. We will also see
gusty east winds develop through the Columbia River Gorge on
Wednesday as the pressure gradient increases across the Cascades.
-McCoy

.LONG TERM...Wednesday night through Sunday...Operational
models and their ensembles suggest a large upper level trough over
the eastern Pacific will continue cool and showery weather over the
region during the second half of the work week. Expect shower
activity to generally be at a minimum during the nighttime hours and
to peak each day during the afternoon and early evening hours.
Thursday definitely looks to be the wettest day in the extended
forecast. While shower chances certainly appear to exist on Friday,
coverage and intensity should be considerably less than Thursday.
Both the EPS and GEFS ensemble means suggest shortwave ridging will
shift across the region over the weekend, but the GEFS is admittedly
a bit faster. As a result, went with a blend of the solutions, which
trended PoPs and sky cover downward and temperatures upwards
Saturday. PoPs were trended closer to climo on Sunday when timing
differences in the shortwave ridge axis shifting across the region
could result in additional wet weather moving back into the region.
/Neuman
&&

.AVIATION...VFR conditions with increasing high clouds this
evening as an occluded front approaches from the southwest. The front
will swing south to north across the region Monday.
Expect rain to begin around 13-15Z Mon in the KONP-KEUG area
then reach KAST-K4S2 by 18-20Z Mon. MVFR conditions are expected
with the front, around 19-21Z KONP-KEUG and 22Z Mon-01z Tue
KAST-KPDX. VFR should return after frontal passage, but may still see
spots of MVFR cigs through Mon evening.

KPDX AND APPROACHES...VFR expected to continue through 21Z Mon,
then increasing chances for MVFR cigs as the occluded front moves
through. Right now think best time for MVFR conditions will be
around 00Z-03Z Tue time frame.East wind develops at the west
end of the Gorge, including KTTD, tonight and strengthens
overnight into Mon morning with gusts 25-35 kt. /mh Weishaar

&&

.MARINE...Wind speeds primarily 15 kt or less through 07Z Mon.
Another splitting front along 130W longitude this afternoon pivots
northeast overnight and Mon morning. The bulk of the energy will
be over the N California and S Oregon waters. There is the potential
for southerly gusts to 25 kt over the southwest portion of PZZ275
and easterly gusts to 25 kt over the north waters late tonight
through Mon morning. Due to the localized nature of these gusts
om the easterly winds, will not issue an advisory. However with
greater potential for south to southwest gusts to 25 kt Mon
through Mon night over all zones, have issued an advisory. Wind
speeds diminish later Mon evening and Tue through late week
under generally weak surface gradients.

Wave heights expected to get just above 10 ft late tonight through
Mon night and will issue a small craft advisory for hazardous
seas with the afternoon forecast. Although total wave heights may
fluctuate at or just below 10 ft, the potential roughness due to
mixed swell supports an advisory. Seas hover in the 6 to 8 foot
range Tue through the end of next week. /mh Weishaar

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds from 11 AM to 10 PM PDT Monday
     for Coastal Waters from Cape Shoalwater WA to Florence OR
     out 60 NM.

     Small Craft Advisory for hazardous seas from 5 AM Monday to 5
     AM PDT Tuesday for Coastal Waters from Cape Shoalwater WA
     to Florence OR out 60 NM.

&&

$$

Interact with us via social media:
www.facebook.com/NWSPortland
www.twitter.com/NWSPortland

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 forecast area.