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Area forecast discussion 
National Weather Service Portland
910 PM PDT sun Apr 26 2015

Synopsis...a warm front off the coast was spreading some light rain
or sprinkles over much of southwest Washington and northwest Oregon
this evening. The warm front will continue to move north tonight and
early Monday...with the light precipitation and clouds decreasing
from the south overnight and early Monday. A building upper ridge in
the wake of the warm front on Monday will bring clearing skies and
much warmer temperatures...with areas inland possibly getting close to 80
degrees Monday afternoon. The next Pacific cold front will move
through on Tuesday for some rain...with a couple of short waves
behind this front moving through Tuesday night and Wednesday for
additional showers...especially from about Salem northward. The
models are trending toward drier flat westerly flow for the remainder
of the week.
&&

Short term...tonight through Wednesday...as advertised...National
Weather Service Doppler radar and National oceanic and atmospheric administration satellite imagery has been
showing clouds and some light precipitation over southwest Washington
and most of northwest Oregon this evening from the eastern end of a
passing warm front. The precipitation will be decreasing from south
to north overnight tonight and early on Monday...and is already
showing that trend in our far southern forecast zones. The associated
building upper ridge will then bring clearing behind the warm front
later tonight and Monday morning..as well as a significantly warming
air mass that could push some inland temperatures Monday afternoon to around
80. The increasing mild air mass and higher dewpoints could also lead
to some local fog or low clouds later tonight and early Monday behind
the warm front.

The next Pacific front will move through the area Tuesday with some
rain over a good part of our forecast area. The best amounts will be
near the coast and in the north. Snow levels will be well above the
passes. Behind the front a couple of short waves move through Tuesday
night and Wednesday that will produce some more showers... especially
from about Salem northward. Snow level Tuesday night and Wednesday
will be lowering but snow amounts will be rather light... with just a
couple of inches at the ski resorts and a skiff at the passes.
Tolleson

Long term...no changes. Previous discussion follows...
Wednesday night through Sunday... residual showers may linger in the
northern zones Wednesday night. Then generally zonal flow aloft will
likely maintain over the region for the second half of the week. A
few weak disturbances may bring occasional light rain at times but
not possible to pinpoint the strength of these impulses and timing of
their arrival at this time. Thus while confidence is improving in the
general pattern and trend...the particulars reflect a lower
confidence forecast. That said...did cut back probability of precipitation a bit for Thursday
Onward given the recent trending of the models...but given some
uncertainty did keep slight chance for the northern
zones...Cascades...and portions of the coast/Coast Range at times.
Despite this...suspect that many locations...including the
central/south Willamette Valley...likely remain largely dry from
Friday into early next next. Temperatures through the extended period
look to remain near normal through early next week. Cullen
&&

Aviation...warm front has brought lowering ceilings into the MVFR
category for all taf terminals over the last few hours. Have also
seen periodic IFR ceilings and visibilities along the coast as some of the rain
bands crossed overhead. Expect these conditions to remain through
about 12z at the coast with ceilings lifting a little earlier for the
inland areas. Low and middle clouds will dissipate during the early
morning hours with a very High Deck remaining in place. Low pressure
will cross from the southwest and a little ways off the pacnw coast.
This will increase easterly pressure gradients across the Cascades
and could produce some 20 to 25 knots gusts at kpdx and kttd tomorrow
afternoon and evening. The coast will pick up a bit of low stratus
roughly after 28/00z.

Kpdx and approaches...MVFR ceilings around 020 will limit overnight
visual approaches. Think these will break up around 09z tonight as a
first guess but it could be as late as 12-15z. Very light rain will
continue at times until then. East winds will increase after 18z with
gusts 20 to 25 knots at times. /Jbonk
&&

Marine...southerly winds have dramatically eased over the last
couple hours and are marginal over a small area at best around buoy
29. Have cancelled the Small Craft Advisory for winds a bit early.
The easing winds let seas ease a bit as well but will continue the
Small Craft Advisory for seas continue until 11 PM as planned. Winds
will largely stay below 10 kts during daylight hours Monday as high
pressure crosses the region. Southerly winds again increase Tuesday
evening reaching Small Craft Advisory criteria overnight through
Tuesday morning from low pressure skirting north and about 300 nm
offshore. Then expect the dynamic swell train to trail the winds by
about 6 hours with seas climbing above 10 feet Tuesday evening.

High pressure returns for the remainder of the week potentially
creating thermal surface low pressure along the northern California
coast. This commonly brings advisory level wind gusts to the central
Oregon waters during the afternoons and evenings. /Jbonk
&&

Pqr watches/warnings/advisories...
or...none.
Washington...none.
Pz...Small Craft Advisory for hazardous seas until 11 PM PDT this
evening for coastal waters from Cape Shoalwater Washington to Cascade
Head or out 60 nm.

&&

$$

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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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