Area Forecast Discussion
Issued by NWS Portland, OR

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408
FXUS66 KPQR 291629
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
928 AM PDT Sat Apr 29 2017

.SYNOPSIS...An upper level ridge will produce dry weather over
southwest Washington and northwest Oregon most of today after a cool
start with patchy fog this morning. The next system will spread some
rain to the north coastal areas late today that will spread across
the area tonight, with decreasing showers on Sunday behind the main
front. Another weakening and splitting system will bring some small
chances of rain to the area Monday into Monday night. Higher pressure
will bring dry and mild weather to the area during the mid week
period, though a warm front might get close to brushing the far north
coast Tuesday or Wednesday. The next system may approach late
Thursday into Friday. More higher pressure is possible next weekend
but there is a bit of uncertainty.
&&

.SHORT TERM...Today through Monday...An upper level ridge is over the
Pac NW today. Most locations are seeing a sunny start to the day,
although visible satellite did show some patchy fog over portions of
the Coast Range and Cascade foothills. Enjoy the sunshine this
morning, but high clouds will be increasing across the region this
afternoon as the ridge axis pushes east of the region. The high
clouds will cap the afternoon high temps a bit, with most of the
lowlands likely topping out in the low 60s.

An occluding low pres system is moving toward the B.C. coast today.
The leading warm front will spread light rain onto the north coast by
late this afternoon, then into the interior this evening. The cold
front will push through overnight. Overall rainfall amounts will not
be all that impressive, with less than 0.25 inch over the interior
lowlands. The coast and higher terrain of the Coast Range and
Cascades should generally be in the 0.25-0.5 inch range with locally
higher amounts possible.

Sunday will see some showers that will decrease through the day as
the low level flow turns more northerly. Snow levels in the Cascades
will stay well above the passes, falling some on Sunday as the
precipitation decreases.

A bit of an upper ridge tries to build in Sunday night but it is
rather flat, of low amplitude. A weak system moves through the ridge
Monday but the models suggest this system will weaken with just some
low chances of any precipitation. Pyle/Tolleson

.LONG TERM...Monday night through Friday...The models say an upper
level ridge will build into the Pacific Northwest Monday night and
Tuesday and likely persist into the first part of Thursday. The main
uncertainty is whether the leading edge of a warm front might brush
the far north coast Tuesday into Wednesday as suggested by the ECMWF
but less so by the GFS. The models suggest some showers may push in
Thursday afternoon and evening, with possibly some instability near
the Cascade crest. The models vary quite a bit after that so will
stick close to climo and keep partly cloudy skies and a slight chance
of showers in the forecast. Tolleson
&&

.AVIATION...High pressure over the Pacific Northwest will bring
VFR conditions today. However, an incoming front will bring a
period of rain and lowering cigs overnight. A mix of MVFR and IFR
conditions appear likely along the coast after 00z Sunday and
conditions should deteriorate to MVFR after 06z Sunday.

KPDX AND APPROACHES...High pressure over the Pacific Northwest
will bring VFR conditions. However, an incoming front will bring
a period of rain and lowering cigs overnight with MVFR
restrictions possible after 06z Sunday. /Neuman

&&

.MARINE...A front dropping southeastward will bring small craft
advisory level wind gusts of 25 to 30 kt to the waters late this
afternoon and evening. The central Oregon waters may have a hard
time reaching these thresholds, but will keep the advisory going
for now given they could still see a couple hours of 21 to 25 kt
gusts. High pressure will then shift back over the waters Sunday
and Monday and bring more quiet weather. A summer-like northerly
wind pattern should develop for a couple days towards the middle
of next week. A westerly swell approaching 10 ft may impact the
waters late in the week, but confidence in this scenario is low.
/Neuman

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 1 AM PDT Sunday for
     Coastal Waters from Cape Shoalwater WA to Cascade Head OR
     out 60 nm.

     Small Craft Advisory for winds from 5 PM this afternoon to 1 AM
     PDT Sunday for Coastal Waters from Cascade Head OR to
     Florence OR out 60 nm.

&&

$$

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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.



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