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Area forecast discussion 
National Weather Service Portland
847 am PDT Sat Mar 28 2015

Synopsis...Post cold frontal showers are mostly confined to the
higher terrain of the Cascades and Coast Range this morning. Showers
will continue to diminish today as high pressure builds and the
atmosphere stabilizes. Dry and mild weather looks to be in store from
late today through Monday afternoon. Another front brings more rain
and cooler weather to the area beginning Monday night and continuing
through next week. Snow levels will likely drop below Cascade Pass
levels during this period.


Short term...showers continue this morning behind the cold front
that moved through the region last night. The upper level shortwave
has now moved well east of the Cascades and weak high pressure is
beginning to build into the Pacific northwest. As a result...the shower activity
is now mainly orographic in nature over the higher terrain of the
Cascades and Coast Range. The orographic showers will gradually
diminish through the day as the low level westerly winds weaken and
subsidence continues to stabilize the atmosphere. The interior
lowlands should remain mostly dry today and may see some sunbreaks at
times this afternoon.

The relatively flat high pressure over the Pacific northwest will bring more dry and
mild weather on sun and much of Monday. atmospheric river
aimed at southwest British Columbia and northwest Washington will
remain close enough that our northern portions of the County Warning Area will see
increased cloud cover compared to their counterparts farther south.
In addition...there is a slight chance that the far northwest zones
may get clipped by a light rain shower or two during this period.

Monday looks like the warmest day this week...but only slightly
warmer than Sunday...with highs in the middle to upper 60s in the valley
and around 60 along the coast and ranging from about 5 to 10 degrees
above normal for this time of year. However rain chances increase
again Monday night as the next front comes ashore. The forecast models
are trending slower with the front with rain chances over land not
really increasing now until after 00z Tuesday and lasting through the
day Tuesday. Models continue to bring snow levels down behind the
front with a few inches of now possible at pass level Tuesday.

Long term...Tuesday night through Friday...a rather active westerly
to northwesterly flow pattern looks to linger across the area with
rain chances every day through the workweek. Models are still
trending toward a break in the action towards next Thursday so have
continued to trend probability of precipitation downward then. Models diverge Friday with the
European model (ecmwf) showing a building ridge while the GFS shows a front
traversing the area. Have favored the wetter GFS solution but nudged
toward climatology pop...about 40 percent right now...due to uncertainty.


Aviation...showers remain over the area in the Post-frontal
air mass...but increasingly confined to the higher terrain of the
Cascades and Coast Range in the westerly flow aloft. Primarily VFR
ceilings across the region this morning with maintain today and become
increasingly scattered this afternoon over the Interior Valley
locations. Meanwhile...lower scattered clouds along the coast may
occasionally form periods of MVFR ceilings and periods of showers will
bring visibility restrictions at times with chances decreasing after 18z
through this evening.

Kpdx and approaches...VFR conditions this morning. VFR ceilings
gradually scattering this afternoon leaving only a broken high
cloud deck. Southerly surface winds around 10 knots through this
evening...becoming light/variable late. Cullen


Marine...westerly winds around 15 knots over the waters this morning
with high pressure building.Are weakening across the waters this
morning as high pressure builds over the waters. Surface pressure
gradient will increase a bit...particularly over the northern
outer between this building high pressure and a low
pressure system in the Gulf of Alaska. Winds will increase in
response tonight and into Sunday...and will likely need to issue
a Small Craft Advisory for the northern outer waters for gusts to
25 knots.

Seas will remain 7 to 9 feet today over the waters...before
increasing again to 10 feet by Sunday afternoon through Monday.
Winds become southerly and increase Sunday night and Monday ahead
of an approaching cold front that will cross the waters Monday
night...with a advisory for winds likely needed. Cullen


Pqr watches/warnings/advisories...
Pz...Small Craft Advisory for rough Columbia River bar until 1 PM PDT
this afternoon.



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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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