Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 282126
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
226 PM PDT Tue Mar 28 2017

.SYNOPSIS...Rain increasing this evening as front slowly approaches
from the west. This front will ensure quite a rain night and most of
Wednesday. Then decreasing showers on Thursday. Still looks like a
nice and mild few days for Fri and Sat, though will see increasing
clouds on Sat. Rain threat, while not all that great, returns for Sun
into early next week.
&&

.SHORT TERM...(Tonight through Friday)...
First, up, due to upgrade with our system, do not have a lot of model
data to look over for the afternoon package. But, even so, not much
has changed in the short term.

Warm front lies well north of the region this afternoon, leaving the
region under cloudy and generally dry conditions. Still have
occasional light rain along the coast and into the coast mountains,
mainly to north of Tillamook. It is mild, with many areas well into
the 50s as of 2 pm.

NOAA satellite imagery shows rather broad baroclinic zone well
offshore, extending from Vancouver Island back to the southwest. This
zone will slowly shift south and east this evening, with rain
spreading across the coastal zones early this evening, and inland
afterwards. May have hard time getting much rain to far southeast
corner of the forecast area, such as eastern Lane and Linn counties.
So, will keep PoPs lowest in that area, but will see spotty rain even
in the area later tonight.

Should be a decent shot of rain, as morning models were showing a
juicy plume of moisture along and ahead of the baroclinic zone.
Precipitable water values of 1.0 to 1.3 inches offshore aimed at
region for later today and tonight. So, seems like good rainfall for
a bit, with 1 to 3 inches tonight and Wed for the coast mountains,
and generally half to locally 1 inch for interior lowlands. But snow
levels rising, up to around 7000 to 8000 feet for tonight and Wed.
So far this fall/winter season, we have had two months with record or
near record rainfall (October and February). Now, with rain expected
over the next 36 hours, could add a third month.

Models agree on dragging the trailing cold front into the region on
Wed am, so will transition to showers in the north zones. But,
another wave on the boundary will approach and move into southwest
Oregon later Wed and Wed evening. Net effect will be to slow the
fronts eastward progression, hanging it up over Lane and Linn
Counties at that time. So, will keep rain into early evening for that
area, then transition to showers late Wed evening once the front
moves east.

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. In fact, Thu likely to be lot like it was
yesterday, with mix of sun and clouds, with decreasing threat of
showers.

Now, for last day of March, or Friday. Appears March will go out like
a lamb, under partly to mostly sunny skies and mild temperatures.
High pressure will bring lighter winds, and good deal of sunshine.
Temperatures in the 50s on the coast, with upper 50s to lower 60s
inland. If Mother Nature cooperates, could even get into the middle
60s from Salem southward.     Rockey.

.LONG TERM...(Fri night through Tuesday)...No changes. Previous
discussion follows. Model agreement is better through Sat,
with a more progressive pattern over the region. Models continue to
show ridging east of the region on Saturday. Still looks dry and mild
on Saturday, with just increasing mid and high clouds. Now, while
there are still differences in the models, will have to keep some
minor threat of showers in forecast for Sat night into early next
week.

&&

.AVIATION...Mostly VFR conditions across the region this
afternoon. Cigs will lower this evening along the coast and near
midnight in the Willamette Valley as a cold front nears and
steadier rain returns...with widespread MVFR conditions into
Wednesday morning. The coast may see occasional IFR conditions
late tonight. South winds could gust to around 30-35 kt along the
coast this evening through Wednesday morning, and to around 25-30
kt in the Willamette Valley.

KPDX AND APPROACHES...VFR conditions this afternoon will
deteriorate to MVFR near midnight tonight with steady rain. S-SE
winds may gust to 20-25kt late tonight into Wed morning. MVFR
cigs will likely persist most of Wed. ~TJ

&&

.MARINE...A low moving along an offshore front has stalled the
cold front just west of 60 nm this afternoon. South winds will
increase over the waters to Gales as the low approaches this
evening and tonight. There will be an additional burst of strong
winds (Gales) with the frontal passage early Wednesday morning.
Seas are a mix of a long-period (16-18 second)and a medium (12
second) period west swells...and steep south wind seas. Combined
seas are expected to build to around 15 ft tonight. Two strong
ebbs could result in breakers around 18 feet in the Columbia
River Bar this evening and Wednesday morning.

The winds will turn westerly and subside behind the front on
Wednesday. High pressure will build Wednesday night and Thursday
and hold through Friday for northwest winds and subsiding seas.
The seas will subside to below 10 ft on Thursday and remain
between 5 and 7 feet through Saturday. ~TJ

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory for winds until 10 PM PDT this evening for
     Coastal Waters from Cape Shoalwater WA to Florence OR out
     60 nm.

     Gale Warning from 10 PM this evening to 7 AM PDT Wednesday 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 9 AM
     PDT Wednesday.

&&

$$

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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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