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Area forecast discussion 
National Weather Service Portland
854 PM PDT Thursday Mar 26 2015

Synopsis...high pressure will lead to another day with above
average temperatures and some morning fog in The Lowlands Friday.
However...a front will spread rain showers into the area late Friday
with potential for thunderstorms near the Cascade crest. Showers
diminish with a drying trend on Saturday. Dry and mild weather looks
to return late Saturday through early Monday. Another front brings
more rain and cooler weather to the area beginning late Monday and
continues into the middle of next week. Snow levels will likely drop
below Cascade Pass levels during this period.


Update...only change was to add patchy fog back to the coast and
coastal valleys tonight as weak onshore flow is keeping dew points
up and much closer to the falling temperatures. Otherwise...the
forecast remains generally on track fro the rest of tonight and
tomorrow. Thunderstorms still seem plausible along the Cascade crest
tomorrow afternoon as instability increases ahead of the approaching
cold front. It's not a slam dunk scenario and feel that the 80
percent chance of it not happening might be a better way to sell it
given increasing clouds to limit surface heating plus weak middle-level
capping. Updates will be available shortly. /Jbonk


Previous disc... /issued 245 PM PDT Thursday Mar 26 2015/

Short term...tonight through Sunday...visible satellite imagery
indicates sunny skies across the area with temperatures climbing
well into the 60s. With a couple more hours of solid
sunshine...expect most interior locations to warm to near 70f. With
mostly clear skies expected overnight...expect more lowland fog to
develop tonight...but coverage should be a bit less than this

A front currently positioned between 130w and 140w will shift toward
the region on Friday. Lift ahead of the upper level trough and
cooling temperatures aloft may initiate a few showers and possibly a
thunderstorm across the Cascades Friday afternoon. Expect the bulk of
the showers associated with the upper level trough to arrive across
northwest Oregon and southwest Washington Friday evening...likely
continuing for much of the night. Rainfall amounts should be
relatively light...likely less than a half inch in the Coast Range
and Cascades...and probably closer to a tenth or two tenths of an
inch in the Willamette Valley.

A lowering subsidence inversion late Friday night should result in
showers becoming increasingly confined to the coast and Cascades
before decreasing further Saturday morning. A relatively Flat Ridge
should then build into the region late Saturday and Sunday and bring
another round of above average temperatures. This should result in
generally dry conditions across the area. However...moisture
streaming northeastward along the edge of the high pressure will take
aim at southwest British Columbia and northwest Washington. As a
result...there is a chance this rain could shift briefly into far
southwest Washington during this period. If nothing else...low to
middle level clouds will likely be a bit more persistent across the
northern portion of our County Warning Area during this period. /Neuman

Long term...Sun night through Thursday...overall pattern remains rather
zonal...with westerly flow aloft over the region. This means fronts
will push across the region from time to time...but no significantly
strong or organized systems expected. After a dry period Sat night
through Sun night...clouds will increase on Monday with another round
of rain for late in the day and Monday night. Likely see showers
continue on Tuesday and Tuesday night as cooler air aloft pushes across
region. Afterwards...confidence in any solution begins to drop as
models diverge on any particular solution. Will trend towards drier
but keep some minor threat of showers with near seasonable
temperatures for second half of next week. Rockey.


Aviation...with high pressure...clear skies...light winds...and a
moist lower atmosphere...conditions are once again ripe for fog
development. As such...expect VFR conditions to give way to
IFR/LIFR ceilings and visibilities around midnight. Once the fog
develops...expect it to remain in place into tomorrow morning
before lifting by late morning. Conditions will briefly return to
VFR tomorrow afternoon...but slowly deteriorate towards MVFR by
tomorrow evening as a cold front moves across the region.

Kpdx and approaches...VFR conditions will give way to IFR/LIFR
ceilings and visibilities after midnight and remain in place through tomorrow
morning. Conditions improve back to VFR tomorrow afternoon...but
should slowly deteriorate towards MVFR tomorrow evening/night as
a cold front moves across the region. /64


Marine...calm weather over the waters will continue into tomorrow
morning as weak high pressure remains over the Pacific
northwest...with winds to 10 knots and seas hovering between 7 and 8
feet. A cold front will push into the waters tomorrow afternoon
allowing winds to increase out of the south. With gust to 25 knots
expected to develop over the outer waters ahead of the front decided
to issue a Small Craft Advisory for tomorrow afternoon. Winds over
the inner waters may briefly climb above 21 knots...but do not feel
they will last long enough or be widespread to warrant an
advisory. Seas will likely climb a little with the strongest
winds...but should remain below 10 feet. /64

Remainder of previous discussion follows...weak high pressure returns to
the waters over the weekend. Another front is expected to move
through on Monday. This front looks a little more impressive and should
bring a solid round of Small Craft Advisory winds...with a small
chance of gales. A more progressive weather pattern for the first
half of next week. Expect seas to reach into the low teens late sun
or Monday and remain above 10 feet for the next several days. Pyle


Pqr watches/warnings/advisories...
Pz...Small Craft Advisory for winds from 1 PM Friday to 3 am PDT
Saturday for waters from Cape Shoalwater Washington to Cascade Head
or from 10 to 60 nm-waters from Cascade Head to Florence or
from 10 to 60 nm.

Small Craft Advisory for rough Columbia River bar from 9 am
to 1 PM PDT Friday.



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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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