Area Forecast Discussion
Issued by NWS Portland, OR
FXUS66 KPQR 272134
Area Forecast Discussion
National Weather Service Portland OR
233 PM PDT Mon Mar 27 2017
.SYNOPSIS...Showers decreasing this evening. But high clouds
associated with the next front will be increasing tonight. Rain
should hold offshore, but clip as far south as Tillamook later
tonight. Rain will gradually spread south and east across the region
later Tue into Tue evening. Will transition to showers Wed afternoon,
with showers into Thu. But, trend for somewhat drier weather on Thu
looking better. In fact, high pres still looks to be enough to keep
Fri and probably Sat dry and mild.
.SHORT TERM...(Tonight through Thursday)...Still have scattered light
showers across the region this afternoon, but these will be
decreasing rapidly this evening. Snow levels hovering around 3000 to
3500 feet, so may still get an inch or two over the higher terrain
through this evening.
Next weather front now sitting well offshore over the Gulf of Alaska,
with preceding thicker clouds increasing this evening. Weak warm
front embedded in these clouds will lift north and east across region
later tonight into Tue am. Looks like will maintain best threat of
rain along the north Oregon coast/coast mountains, extending
northeast across western Washington. Will keep some minor threat of
rain to south, but not much in way of precipitation expected for
In fact, with the warm front lifting north of the region on Tue, will
see some thinner spots in the clouds to south of Salem. Generally,
will keep areas south of a Lincoln City to Portland line dry for Tue
afternoon. With mild air mass, temperatures will stay in the middle
to upper 50s. If can get some bigger breaks in the cloud cover on
Tue, would not be surprised if areas to south of Salem break into the
lower 60s. Meanwhile, freezing levels will be on the rise later Tue
and Tue night, running between 7000 and 8000 feet Tue night into Wed.
Models continue to show the cold frontal boundary approaching Tue
night, with rain spreading back to the coast in the evening, then
spreading inland overnight. The cold front will buckle inland Wed am,
with rain transitioning to showers by Wed afternoon. But, will see
low pres on the front develop off the south Oregon coast. This will
act to hold up the front, and slows its inland progression. So, will
likely see rain continue all day on Wed for areas south of Newport to
Salem to Mt Hood. Precipitable water values running fairly high, as
this front will have prior tapped some moist subtropical air. Will
keep mention of locally heavy rain for the coast, Coast Range, and
Willapa Hills for later Tue night into Wed am. Rather modest rainfall
expected for Tue night and Wed expected, with 0.75 to 1.50 inch on
the coast, with 1 to 2 inches in the Coast Range/Willapa Hills.
Farther inland, generally 0.50 to 1.00 inch likely for the lowlands,
with 0.75 to 1.50 inches in the Cascades. Unfortunately, this will
fall as rain for the Cascades, thanks to the elevated freezing
Once the frontal boundary shifts farther south and east, likely Wed
evening, will see showers gradually decrease. Upper trough axis will
shift over the region late Wed night into Thu am, with best threat of
showers at that time. Thu likely to be similar to today, with a
decreasing shower threat as the day progresses. Rockey.
.LONG TERM...(Thu night through Monday)... Model agreement is better
through Fri and Sat, with a more progressive pattern over the region.
Models continue to show ridging over the region by Fri, with dry and
mild temperatures. Still differences in the models, but will maintain
dry weather into Sat. But, will trend back to some chance of showers
for Sat night and Sun as will see another front shift across the
region at that time. With the progressive pattern, will see fronts
moving across the region about every 2 days. So, after Sunday, will
transition to another decreasing shower day on Monday, with
potentially another dry day or two to start next week. However, since
it is spring and Mother Nature can get feisty at times, will keep
some mention of showers to start next week. Rockey.
.AVIATION...Shower coverage will continue to decrease this
afternoon with the occurrence of MVFR conditions also becoming
less likely. Once the showers come to an end shortly after sunset
the weather will be quite benign through the remainder of the
KPDX AND APPROACHES...Mostly VFR conditions. Slight chance of
MVFR cigs/visibility if any heavier showers move through the
terminal this afternoon, but likelihood and longevity is small
enough that it is not worth mentioning in the TAF. /Bentley
.MARINE...Square seas around 10 feet at Buoy 50 will continue to
increase into the overnight hours to near 14 feet after sunset.
Seas will remain in this 13 to 15 foot range through Wednesday,
but only have the small craft through 06Z Wednesday as there is
a chance of gale force winds building in by late Tuesday night
which may necessitate an upgrade to a gale warning. Beyond
Wednesday, seas will drop below 10 feet and remain there through
the middle of the weekend.
In addition to the increasing seas, winds will also strengthen
tonight with gusts approaching 30 knots by tomorrow morning.
These stronger winds will persist through the day Tuesday and
into Tuesday night before strengthening ahead of a surface low
early on Wednesday. During this time, wind gusts may approach 40
knots for most of the waters. There may still be some lingering
small craft winds during the day on Thursday, but once winds drop
below 20 knots, they will remain there through at least the
first half of the weekend. /Bentley
PZ...Small Craft Advisory for winds from 11 PM this evening to 11 PM
PDT Tuesday for Coastal Waters from Cape Shoalwater WA to
Florence OR out 60 nm.
Small Craft Advisory for hazardous seas until 11 PM PDT Tuesday
for Coastal Waters from Cape Shoalwater WA to Florence OR
out 60 nm.
Small Craft Advisory for Rough Columbia River Bar until 11 PM
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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.