Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 281017

Area Forecast Discussion
National Weather Service Portland OR
317 AM PDT Tue Mar 28 2017

.SYNOPSIS...A warm front approaching WA and northern OR will
bring increasing chances for rain to the region today and tonight. A
cold front will move se through OR Wed, turning rain into showers
Wed and Wed night. Showers will continue through Thu, but drier
weather is in store for Fri as a ridge of high pres moves across.

.SHORT TERM...(Today through Thursday)...A surface ridge of hig pres
over western Oregon early this morning is expected to shift into
southern Oregon today and tonight. This will eventually deepen the
onshore flow and moisture over the region. A warm front is expected
to approach the region late tonight as a low pres center heads up
towards Vancouver Island Wed morning. Isentropic lift will increase
and lower ahead of the warm front. Today, the moist isentropic lift
will tend to be weak and primarily confined to mid levels. Prefer to
keep some mention of light precipitation over all but the far
southern part of the forecast area given the current distributution
of light rain over the area and the weak lift. Tonight pops quickly
increase to categorical as models develop stronger moist isentropic
lift with a strengthened sw flow on the order of 40 to 50 kt along
the 290k isentrope just a few thousand feet msl. With plenty of
clouds and the approach of the warm front, temps should remain mild
tonight with snow levels rising well above Cascade passes by Wed

Models agree on dragging the trailing cold front se through the
forecast area Wed and Wed evening. With deep moisture preceding the
front chances for rain will remain categorical Wed morning, then
remain high across the south part of the area Wed afternoon and
evening as the baroclinic zone may be a little slow to clear the
region as the front becomes closer to parallel with the upper flow.
Behind the front a cooler air mass moves in, with the cold upper
trough moving through late Wed night into Thu morning. Expect
showers to become more orographically favored once the upper trough
passes Thu morning.

.LONG TERM...(Thu night through Monday)...No changes. Previous
discussion follows. 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./mh  Rockey.


.AVIATION...A warm front moving onshore this morning will bring
light rain or drizzle and a mix of VFR and MVFR to SW Washington
and far NW Oregon this morning. KAST and the northern Willamette
Valley TAFs will likely drip to MVFR at times. Conditions should
become mainly VFR behind the frontal passage by around 15Z as the
rain lifts north of the fcst area. The trailing cold front will
move through from NW to SE late tonight into Wed morning. This
will likely bring widespread MVFR conditions.

KPDX AND APPROACHES...Light rain or drizzle and occasional MVFR
cigs expected through around 15Z with a warm front approaching.
Conditions improve after 15Z with VFR expected through the rest
of today. Rain will increase again between 06Z-12Z Wed, with
conditions likely deteriorating to MVFR. Pyle


.MARINE...A warm front is moving through the waters this morning.
The trailing cold front will move into the waters later today and
stall. Expect persistent small craft advisory southerly winds
through tonight, with winds generally 20 to 25 kt with gusts to
35 kt. A low will form along the stalled frontal boundary and
approach the waters from the southwest late tonight into Wed
morning. The fcst models continue to indicate that the low will
strengthen winds further, with gusts to 35 kt possible overnight.
Have issue a Gale Watch from late this evening through Wed
morning. The cold front will move onshore during the day Wed, and
winds will turn westerly and subside behind the front. High pres
will build in Thu and remain through at least the first half of
the weekend. This will bring a period of benign weather with
northerly winds over the waters.

Seas will remain 13 to 15 ft through Wed. Hanson plots and
spectral guidance suggest a 11 to 12 second swell set and a
longer-period 17 to 18 second swell train through today. Then the
longer period swell will take over Wed. Seas drop below 10 ft Thu
and remain low through the next few days. Pyle


PZ...Gale Watch from this evening through Wednesday morning for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     60 nm.

     Small Craft Advisory for winds until 10 PM PDT this evening for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     60 nm.

     Small Craft Advisory for hazardous seas until 10 PM PDT this
     evening for Coastal Waters from Cape Shoalwater WA to
     Florence OR out 60 nm.

     Small Craft Advisory for Rough Columbia River Bar until 11 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. is the U.S. government's official web portal to all federal, state and local government web resources and services.