Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 252143
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
242 PM PDT Sat Mar 25 2017

.SYNOPSIS..Showers end this evening. But the next round of rain will
push into the region later tonight as another front arrives. Rather
wet day for Sunday, then showers for Sun night and Monday. Wet
weather continues Tue and Wed. But, starting to see some hope for a
day or two of dry weather towards end of next week.

&&

.SHORT TERM...(Tonight through Tuesday)...Plenty of clouds across
region this afternoon into this evening. Still a few lingering
showers, mainly over the higher terrain. But, those showers will end
this evening.

Next front offshore is fast approaching, thanks to a 120 kt jet
pushing on it. This appears to be bit faster than morning models
were thinking. But overnight, this front will slow down a bi as it
gets farther away from its parent low, which will remains over the
Gulf of Alaska. So, will have increasing clouds this evening, but
still think will remain generally dry, aside from the aforementioned
lingering showers. Will boost PoPs for late tonight, as think the
rain should start on the coast between 2 and 5 am Sunday. Then will
see rain spread across all of the forecast area Sunday am. The front
will push onshore later Sun afternoon, and pushes across to the
Cascades during the early evening.

While not all that impressive, precipitable water values continue to
support moderate rain at times on Sunday, especially in the
afternoon. Generally, a 0.25 to 0.50 inch of rain would be a good bet
for most areas, and 0.75 to 1.25 inches for the Willapas and Coast
Range, and bit less into the Cascades. Snow levels will stay up
around 4000 to as high as 5000 feet on Sunday, then will lower behind
the front to around 3500 feet. While higher elevations of the
Cascades will see snow, on Sunday, thinking that will not all that
much at pass level until Sun night. Will not put up a snow advisory
for the Cascades, even though will get a decent shot of snow later
Sunday afternoon through Sunday night, with additional snow on
Monday. At this time, would expect total of 10 to 15 inches in the
higher terrain, with 3 to 8 inches at passes. But, not sure if would
get enough snow fast enough to support winter weather advisory, as
the accumulations will be spread out from Sunday afternoon through
Monday morning. Higher terrain, could be. Will let next few shifts
reevaluate this potential.

Cool onshore flow will persist into Monday as the upper trough moves
across the Pac NW. Temps likely remain a little below late March
normals for the next few days.

Models continue to show another front, albeit weaker, trying to push
into the region on Tue. At moment, not convinced it will amount to
much and will take most of the day for the moisture to spread across
the area. For now, will keep generally chance PoPs for most inland
areas, and higher PoPs of likely to higher for the coast areas,
especially north of Newport. What is left of the boundary will spread
farther inland Tue evening.

.LONG TERM...(Tuesday night through Saturday) Upper-level pattern
becomes more amplified later next week, behind a trough that will
bring more rain Tuesday night into Wednesday, transitioning to
showers on Thursday. This means a ridge builds up over the Pacific
Northwest Friday for a dry and mild day. Models are in remarkably
good agreement with this ridge for how far out it is in the forecast
period, increasing confidence. Models however have the ridge
flattening with an approaching broad trough, with significant
differences in timing between the ECMWF (Saturday) and the GFS
(Monday). Either scenario will bring rain back to the area with the
flattening of this ridge. Snow levels generally hover around 4000 to
5000 feet, except for Wednesday and Friday when they go up to 6-8000
feet. Temperatures generally remain a little cooler than normal.
-McCoy
&&

.AVIATION...Showers have just about peaked in intensity and
coverage for today. Conditions generally remaining VFR with
broken Cigs around 050 with a lower scattered deck 030-035. High
clouds arriving tonight should limit the threat of low clouds and
will continue the idea of VFR cigs through the night and into
early Sunday. Should start seeing some MVFR cigs developing
under the increasing rain after 26/18z at the coast and possibly
inland after 21z.

KPDX AND APPROACHES...Showers beginning to decrease over the next
couple hours. May see brief cigs 035-040 affecting visual
approaches through 00z today. Otherwise next impact to flight
conditions will likely not be until after 26/21z when frontal
rain intensifies and cigs lower, possibly reaching 025. /JBonk


&&

.MARINE...Weak high pressure exits east tonight with an upper
trough approaching late overnight. Seas are currently 8-9 feet
but with dominant periods now stretching out to 13-15 seconds,
feel good about letting the SCA for seas run it`s course this
afternoon. No changes for the gale warning with the afternoon
package. Higher resolution models are showing gap winds 35-40 kt
which is on the lower end of gale gust criteria and did include
them as well, albeit for a shorter time window. The models
increased overall speeds by a few knots and that appears to be
pushing seas up by a couple feet as well. Now expect peak seas of
15-17 feet mainly about 35 nm and further offshore where the
wind fetches are better under the early slightly SSE winds.
Closer waters will still see seas reach the lower teens. Winds
will quickly ease following the cold front passage during the
afternoon while seas may take several hours to follow.

There will be a lull in the winds Sun night and Mon, but another
front is expected to impact the waters on Tue into Wed. There is
some model disagreement with the track and timing on this
system, but it looks likely that it will result in some small
craft advisory winds. A longer period westerly swell is modeled
to arrive Mon night into Tue, which would push seas back above 10
ft. The additional wind wave energy from the frontal system
could bring seas back into the mid teens Tuesday. Models then are
leaning on high pressure building offshore bringing northerly
flow for Thursday and early Friday. JBonk/Pyle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Gale Warning from 6 AM to 3 PM PDT Sunday for Waters from Cape
     Shoalwater WA to Florence OR from 10 to 60 nm.

     Small Craft Advisory for hazardous seas until 4 PM PDT this
     afternoon for Coastal Waters from Cape Shoalwater WA to
     Florence OR out 60 nm.

     Gale Warning from 11 AM to 4 PM PDT Sunday for Coastal Waters
     from Cape Shoalwater WA to Florence OR out 10 nm.

     Small Craft Advisory for Rough Columbia River Bar until 6 PM
     PDT this evening.

&&


$$

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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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