Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 260412
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
904 PM PDT Wed May 25 2016

.SYNOPSIS...A deep marine layer will continue to bring cool
temperatures and some areas of light drizzle primarily along the
coast and Cascade foothills Thursday. A low pressure system skirting
our northern zones will keep temperatures near average over the
weekend with light rain chances primarily confined to southwest
Washington and the Oregon coast. Strengthening high pressure looks to
bring drier and warmer weather early next week.

&&

.SHORT TERM...Tonight through Saturday...A deep marine layer remains
entrenched across northwest Oregon and southwest Washington this
evening. Clouds were slow to clear across most of the region this
afternoon and what holes in the cloud cover exist this evening should
fill back in overnight as onshore pressure gradients have nudged
upward a couple millibars versus 24 hours ago.

Many areas in the coast range and a few locations along the immediate
coast and in the Cascade foothills received enough lift to generate
measureable drizzle and light rain earlier today. Given the marine
layer will persist into tomorrow and pressure gradients will remain
elevated, if not, nudge upward another millibar or two, we should see
another round of drizzle/light rain along portions of the coast and
coast range. PoPs were nudged upward over locations that experienced
measurable rain today. The chances of this wet weather making its way
inland appear highest along the lower Columbia River Valley and near
the Cascade foothills, but confidence that it will develop remains
low given ceilings along the coast remain up near 3-4kft.

A shortwave trough currently approaching Haida Gwaii will move into
southern British Columbia and northern Washington Thursday and linger
over this general region for much of the upcoming Memorial Day
weekend. As a result, onshore flow will persist and keep cloud cover
somewhat elevated especially during the morning and midday hours.
Besides the general cool airmass overhead, this should also help to
keep temperatures near to slightly below average.

Given the deepest instability accompanying the aforementioned
shortwave trough will remain well to our north, rain chances will be
somewhat limited and primarily confined to our northern zones Friday
through Sunday. Those residing in our far southern zones including
Lane, Benton and Linn Counties stand a decent chance of remaining
dry the entire weekend. /Neuman


.LONG TERM...Saturday night through Wednesday...While still some
uncertainty concerning the depth and precise strength of the upper
low, confidence continues to increase that the upper level low
moving south from B.C. over the weekend will take a more inland
track. However, with the upper level trough remaining over the
region on Sunday, a reinforcing shortwave will bring the potential
for some showers across the area. By late Sunday into early Monday
the trough shifts east as a upper ridge near 135W amplifies and
heights begin to rise over the region. Maintained a slight chance
PoP across the extreme northern coastal zones as well as portions of
southwestern Washington for Monday, but suspect that Monday will be
largely dry and warmer, back to near or a few degrees above seasonal
normals. As the upper ridge strengthens and moves over the region
during the early part of next week, expect temperature to further
warm - possibly nearing 80 degrees inland on Tuesday and Wednesday.
However, some differences emerge in the forecast models by midweek
with the GFS suggesting a slightly cooler pattern, so confidence is
only moderate for the end of the long term period.    Cullen


&&


.AVIATION...Mostly VFR conditions through the TAF period. The
exception will be after midnight tonight through tomorrow morning
where MVFR cigs are expected in most cases. Latest model guidance
indicates the break in the cigs along in the western half of the
Willamette Valley will remain consistent through the overnight
hours without much additional growth. This could cause conditions
at KEUG, KSLE, and KHIO to jump between SCT, BKN, and OVC through
the overnight hours.

PDX AND APPROACHES...Cigs expected to lower through the evening
and settle around 3500 feet by ~8Z. Winds expected to remain light
and somewhat variable until later in the day Thursday. /Bentley


&&


.MARINE...Have been watching Buoy 46089 this evening with
sustained winds between 14 and 16 kts and gusts adding only a few
knots to these numbers. Will keep the Small Craft Advisory for
Winds out for now since the strongest winds are expected between
now and 15Z Thursday. Otherwise, winds will switch around
southwesterly for a a period on Saturday as a front moves through
the area. Some gusts may reach small craft advisory strength ahead
of this front. Seas will remain fairly benign through the weekend
in the 4-6 foot range with an ~8 second swell. /Bentley


&&


.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 5 AM PDT Thursday 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. The area is
commonly referred to as the forecast area.


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