Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 270936
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
236 AM PDT Thu Apr 27 2017

.SYNOPSIS...Strong NW flow aloft will bring continued showers today
and snow levels will remain near or just below the Cascade
passes. There will be a break in the weather Fri and
Sat, with dry and milder conditions. A weakening cold front will
bring the next round of rain Sat night into Sun. The trend is then
toward drier and warmer weather as an upper level ridge strengthens
over western North America. With any luck, it may actually feel like
spring next week.

&&

.SHORT TERM...(Tonight through Sat)...Big pattern change appears to
be on the way going into next week.  For now we remain on the north
side of a strong Pacific jet, keeping orographically driven showers
across the area overnight. Little change through Thursday as we
remain on the north side of the strong Pacific Jet with persistent NW
flow aloft keeping decent orographic flow into the Cascades. Expect
shower activity to remain primarily over the Cascades and higher
terrain of the Coast Range. Snow levels hover around 3000-4000 ft and
several inches of snow are expected above the passes.  Some
uncertainty around the passes as yesterday showed that even with snow
levels right around the passes, snow just issn`t sticking very well
to roads due to road temperatures. As daytime temperatures start to
increase, expect shower activity to pick up across the lowlands
Thursday afternoon. Don`t expect showers to be deep enough to support
thunderstorm development, but wouldn`t be surprised to see an
isolated lightning strike or two in the afternoon if we get enough
sun breaks.

Pattern starts to shift Thursday night into Friday as what we`ve all
been waiting for, a large-scale upper-level ridge, starts to build
into the Pacific Northwest. This will be a major player in the
weather going into next week, helping to keep us drier and warmer,
possibly even unseasonably warm next week. As the ridge builds in,
showers will come to an end for a mostly dry day on Friday with
decreasing clouds. Ridge remains over the area into Saturday, keeping
dry and mild conditions. Will see increasing high clouds Saturday
afternoon ahead of a weak shortwave that rides over the ridge
Saturday night into Sunday. -McCoy

.LONG TERM...(Sat night through Wed)...A low pres system is modeled
to move into British Columbia late Sat, bringing a weakening cold
front onshore into Washington and Oregon Sat night. The fcst models
currently suggesting light rain develops on the coast Sat evening,
then moves through the interior overnight into Sun morning. Scattered
post-frontal showers likely lingering through much of Sun. Then the
upper ridge over the NE Pac is modeled to gradually strengthen again
over the Pac NW for the first half of next week. The ridge may not be
quite strong enough to prevent a few showers around the area Mon or
Tue, so will keep low chance PoPs in the fcst for now. By Wed, it
appears that the ridge strengthens considerably over the region. Most
of our fcst models now suggesting highs reaching into the 70s over
the lowlands Wed afternoon. Hopefully we have not jinxed it, but we
have gone with 70s in the fcst. Pyle

&&

.AVIATION...Cool and unstable onshore flow continues, with
scattered showers increasing again this am. Flight conditions
generally remain VFR across the region, but will see brief MVFR
under the heavier showers today. Showers will decrease after 03Z,
with VFR cigs remaining through good part of the evening.

KPDX AND APPROACHES...VFR conditions through this evening, with
cigs running at 4000 to 5000 ft. Scattered showers increasing
this am, and may see brief MVFR under heavier showers between
15Z and 22Z.     Rockey.
&&

.MARINE...For the most part, rather benign pattern continues with
winds mostly 15 kt or less. But seas holding at 8 to 9 ft today
into early this evening, then seas will slowly subside.

High pressure over the region Fri and Sat, with winds generally
15 kt or less with seas 5 to 7 ft. A front will push across the
region on Sunday, but with slight boost in winds and seas. A
stronger front will push across the region on Tue, but appears
strongest winds still hard pressed to reach 20 kt.    Rockey.


&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for Rough Columbia River Bar conditions
 until 8 am today...and again 5 pm to 8 pm today.

&&

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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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