FXUS66 KPQR 262140
Area Forecast Discussion
National Weather Service Portland OR
238 PM PDT Sun Mar 26 2017
.SYNOPSIS...And the wet weather continues. Cold front getting close
to the coastline, and will push across the region later this
afternoon. Snow continues to fall in the Cascades, especially above
the passes. Showers continue on Mon, but will see brief break in rain
on Tue. But, that short lived as another round of rain will spread
into the region Tue night. Still looks good for a break with dry and
mild conditions as we close March later this week.
.SHORT TERM...(Tonight through Wednesday)...Cold front is now just
whiskers offshore as of 230 pm, and will onshore shortly. The front
will move fairly quickly inland over next several hours, and should
be nearing the Cascades crest by 6 pm. So, steady rain will
transition quickly to showers once the front passes.
Meanwhile, snow levels still holding near 4000 to 5000 feet, highest
over Lane County. But these will drop back down behind the front
tonight, generally sitting at 3000 to 3500 feet. While precipitation
will become more showery this evening, still think good potential for
3 to 8 inches of snow at the passes for tonight through Monday, with
8 to 15 inches at higher elevations. So, will maintain current winter
weather advisory for the Cascades through Mon afternoon.
Cool pool aloft will shift over the region tonight and Monday, but
still looks like timing will be key for the stronger showers. Will go
with models suggestion, which takes the core of the cold pool over
the region late tonight and Mon am. This would provide for some hefty
showers at that time, and perhaps a thunderstorm or two along the
coast and offshore. As day progresses, will see some slight warming
aloft, with showers slowly decreasing. May not be until late in the
afternoon before see significant decrease of showers over the higher
terrain of the Cascades.
Weak high pres builds into the region later Mon night and early Tue,
but will be rather transient as another frontal boundary to our
northwest will slowly approach. Plenty of clouds over region on Tue
with some spotty rain for areas north of a Newport to Portland line.
Still think areas inland to south of Salem will be mostly dry on Tue.
Will maintain this trend. However, it not out of the question that
the rain threat may shift bit northward on Tue, with more areas
inland being dry.
But makes no matter, as that front will sag southeastward into the
region Tue night. Will see increasing rain at that time. Models have
hinted as some upper level moisture enhancement with this system, so
could see locally heavy rain over the Coast Range and Willapa Hills
late Tue night into Wed am. Fairly potent low pres area will pass to
our northwest Wed am, with cold front pushing inland later Wed am
into early afternoon. Pressure gradients do tighten, probably enough
to produce breezy conditions with gusts 40 to 50 mph at times along
the coast in the morning. Then back to showers with moderate onshore
flow for Wed afternoon. Rockey.
.LONG TERM...(Wednesday night through Sunday) Upper-level ridge
builds over the Pacific Northwest late this week. This means
decreasing showers on Thursday with clearing skies Thursday night. A
dry sunny spring day is in order for next Friday, as the models are
in good agreement with the ridge moving over the Pacific Northwest.
Models diverge on how quickly the rain returns. ECMWF flattens the
ridge bringing rain back on Saturday, while the GFS doesn't flatten
the ridge until Sunday. ECMWF has been more consistent with the
ridge breaking down on Saturday, so this is more likely the scenario
we will see. However, there is still a chance for a dry day for at
least the southern half of our area. By Sunday night, the chance of
rain goes up even more with a wet pattern returning for next week.
Snow levels come back down to 3000 to 4000 feet behind the front on
Thursday as showers are winding down. With the ridge building in on
Friday however, snow levels come back up to around 6000 to 8000 feet
for the next system Saturday or Sunday. Temperatures start a bit
cooler than normal on Thursday, rising to around normal Friday
and hovering near normal through the weekend. -McCoy
.AVIATION...In a period of MVFR cigs/visibilities for most of the
area. This will be short lived and should begin to improve by 00Z as
the front moves through the area. Behind the front, scattered
showers can be expected for the next 24 hours with VFR conditions
except for occasional MVFR cigs/visibilities during the heaviest
showers. Gusty south winds along the coast will also come to an end
this afternoon and will be less than 15 knots in the wake of the
KPDX AND APPROACHES...Occasional MVFR cigs and visibility this
afternoon ahead of the front will improve to VFR by this evening.
Rain showers will continue for the next 24 hours.
Conditions will be mostly VFR through this period except for any
stronger showers when conditions may temporarily become MVFR.
.MARINE...The front has moved through most of the waters and will
be onshore by 3 to 4 pm this afternoon. This will bring an end to
the gale force winds over the waters. Winds will quickly fall to the
10 to 15 knot range behind the front, but seas may stay up just long
enough that a short term small craft advisory for seas may be
needed. Will wait until right up to the expiration time of each
product before making a decision.
Benign marine weather conditions will prevail through Tuesday
morning when winds increase ahead of an approaching front. This
front will stall northwest of our area and keep our area in an
extended period of small craft advisory strength winds through mid
week. Models have come into agreement that a surface low will
develop along this front Tuesday night and track towards Vancouver
Island. This strengthening low will likely bring another period of
gale force winds to the Oregon and Washington coastal waters. Given
this is still over 48 hours out, will not issue a gale watch at this
time, but anticipate one will be needed. Beyond this time, and
extended period of high pressure develops over the Pacific NW,
ushering in several days of calm weather.
Despite the calm winds on Monday, seas will come up as a long period
swell from the WNW pushes into the area and brings seas up to the 13
to 15 foot range by the evening. Seas will remain in this range
through the Wednesday storm before settling below 10 feet towards
the end of the week. /Bentley
OR...Winter Weather Advisory until 4 PM PDT Monday for Cascades in
Lane County-Northern Oregon Cascades.
WA...Winter Weather Advisory until 4 PM PDT Monday for South
PZ...Gale Warning until 4 PM PDT this afternoon for Coastal Waters
from Cape Shoalwater WA to Florence OR out 10 nm.
Gale Warning until 3 PM PDT this afternoon for Waters from Cape
Shoalwater WA to Florence OR from 10 to 60 nm.
Small Craft Advisory for Rough Columbia River Bar until 7 PM
PDT this evening.
Small Craft Advisory for Rough Columbia River Bar from 3 AM to
7 AM PDT Monday.
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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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