Area Forecast Discussion
Issued by NWS Portland, OR
FXUS66 KPQR 271605
Area Forecast Discussion
National Weather Service Portland OR
905 AM PDT Fri May 27 2016
.SYNOPSIS...Onshore flow will maintain plenty of clouds across the
region today and into this weekend, along with a few showers.
Greatest chance of showers will generally be north of a Tillamook to
Mt Hood line. As high pressure builds over the region later Sunday,
showers threat will end, with dry and warmer temperatures for Monday.
High pressure will dominate the pattern for next week, with warm and
rather warm conditions as inland highs reach well into the 80s.
.SHORT TERM...(Today through Sunday)...A look at NWS Doppler radar
this morning shows fairly widespread shower activity over the
northern half of the forecast area. However, precipitation totals are
light, generally on the order of a trace to a few hundredths of an
inch at most. The shower threat will remain through the afternoon,
remaining mainly over the northern portions of the fcst area.
Otherwise, expect mostly cloudy skies with perhaps a few sun breaks
developing this afternoon. Highs today will be on the cooler side,
only reaching into the low 60s for the interior lowlands.
A broad area of low pressure remains over the Pacific NW through the
weekend, with cooler northwesterly flow aloft into the region. This
will maintain plenty of clouds over the region today through Sunday,
with partial clearing at times in the later afternoons/evenings. But
not a big threat of moisture. Most of the instability will remain
over Washington and over far northwest corner of Oregon. Another
weak upper level disturbance with a weak front will drop into the
region on Saturday, but again, best threat of showers will over
Washington, and perhaps down as far south as a Lincoln City to Mt
Hood line. Even so, showers will be much more hit and more miss as
system is fairly weak and little punch.
Sunday will be our transition day, with cloud cover gradually
breaking up late in the day. Temperatures will return to seasonable
levels (lower 70s inland), thanks in part to more sunshine,
especially to south of Portland. Will cut back further on threat of
showers, but can not completely eliminate the threat. So, will remove
threat of showers for areas south of a Lincoln City to Salem to Mt
Jefferson line, but will keep 10-20 percent chance to the north of
that line due to continued onshore flow over region. But by evening,
even that threat will nearly end. Pyle/Rockey.
.LONG TERM...Sunday night through Wednesday...Ridging begins to build
in Sunday night, making for dry and warming conditions starting
Monday. Memorial Day itself is currently looking lovely with clearing
skies and temperatures in the mid to upper 70s inland and even some
mid to upper 60s along the coast. Tuesday should be similarly dry and
sunny, but warmer, with inland temperatures approaching the mid 80s
as flow turns offshore. Models disagree regarding when the ridge will
break down with the earlier models suggesting rain chances creeping
back into the forecast Wednesday while others hold off until Thursday
or even later. If the earlier models are right, an upper low to the
SW of the area could put us in a favorable pattern for thunder at
least in the Cascades starting Wednesday afternoon, but confidence at
this point is low. Bowen
.AVIATION...VFR conditions to prevail across the area through
this evening, despite plenty of cloud cover. A few -SHRA could
cause brief periods of MVFR cigs along the coast. A few -SHRA
inland as well, but probably not heavy enough to cause significant
PDX AND APPROACHES...VFR conditions through this evening with
occasional -SHRA. Cigs should remain around 5000 ft. -McCoy
.MARINE...No changes. Previous discussion follows...
W-NW flow continues across the coastal waters, with strong high
pressure over the NE Pac and lower pressure over British Columbia.
This will guide a weak low/front into the WA waters Sat, causing
winds to back to S-SW. May eventually need a SCA for winds for our
northern waters as 25 kt gusts will be possible, especially in any
weak coastal jet that forms with the front. High pressure will
follow with lighter winds on the coastal waters Sunday. Northerly
flow will increase up the coast early next week as warmer weather
causes a thermal trough to build northward along the California
and Oregon coast.
Seas will be rather benign through the forecast period; generally
6 feet or less. With very little swell component, seas will
primarily be wind or fresh swell driven. -McCoy/Weagle
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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.