Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
324 PM PDT sun Apr 26 2015
Synopsis...a weakening warm front offshore will bring some light
rain to parts of the area mainly tonight. High pressure aloft will
prevail on Monday. This combined with weak low level offshore flow
will result in well above normal temperatures. Look for a cold
front to sweep across the region on Tuesday for cooler
temperatures. Low pressure aloft will keep the weather unsettled
a weakening warm front offshore will continue lifting north
towards British Columbia. Thus far...occasional light rain has
been confined to mainly the coast. Not expecting much in the way
of precipitation overnight...so probability of precipitation were cut back over much of the
Meanwhile...an upper ridge will amplify over the region through
Monday. This combined with light low level offshore flow will result
in well above normal temperatures across the County Warning Area. The upper ridge will
into the interior west Monday night...allowing an upper trough and
associated cold front to approach the area. The front will move
across the County Warning Area during the day Tuesday. A Puget Sound sound convergence zone
/pscz/ will likely develop behind the front due to increased
westerly flow through the Strait of Juan Delaware fuca. Daytime temperatures
will return to near normal on Tuesday.
An upper trough will prevail over the Pacific northwest Tuesday night
and Wednesday for cool and unsettled conditions.
the medium range solutions continued to disagree and have trouble
maintaining consistency...thus the forecast confidence in this
period was low. The latest solutions were trending toward an upper
ridge during the end of the period...however not sure this trend
will continue to hold. Consequently...kept a risk of showers in
the forecast. Temperatures should be near normal during this period.
Aviation...an upper ridge will be over the Pacific northwest
tonight and Monday with southwest flow aloft. A weakening warm front
will move onshore tonight. Air mass stable.
Mostly middle level clouds across the area early this afternoon. Low
levels will gradually moisten tonight. Ceilings are expected to
mainly be 4000-6000 feet over the interior tonight with 2000-4000
foot ceilings towards the coast. Clouds should lift and scatter on
Ksea...middle level clouds this afternoon. Ceilings expected to
gradually lower to 4000-6000 feet this evening. Southerly wind 4-8
Marine...a weakening warm front will bring small craft southerly
winds to the coastal waters and West Entrance Strait of Juan Delaware fuca
tonight. Winds could also rise to Small Craft Advisory levels for a
few hours this evening over some of the north interior waters but
the forecast is 10-20 knots for now.
In general winds will ease later tonight and Monday as the front
moves inland. Small Craft Advisory south winds will probably linger
through at least Monday morning for the northern coastal waters
before easing. There should also be a brief west push in the Strait
later Monday but the details are a bit muddled as a second front
will already be approaching from the west.
The aforementioned second frontal system will bring another round of
Small Craft Advisory southerly winds to most waters early Tuesday.
Moderate onshore flow behind the front later Tuesday is expected to
bring Small Craft Advisory west winds to the Strait. Gale force west
winds are possible if the stronger GFS verifies. A third front will
probably reach the area Wednesday. Schneider
Pz...small craft advisories are in effect for the coastal waters
and West Entrance to the Strait of Juan Delaware fuca.
You can see an illustrated version of this forecast discussion at