Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
245 PM PST Monday Feb 8 2016
Synopsis...low level offshore flow today will continue through
Tuesday with an upper ridge of high pressure over the area. The high
will weaken and move east on Wednesday as a weak front reaches the
coast. Weather systems embedded in the southwesterly flow aloft will
move through western Washington Wednesday night through Saturday.
Short term...a strong upper ridge and offshore surface flow has
brought unseasonably warm conditions to the area today. Temperatures
will peak in the 60s today in many locations...including Paradise on
Mount Rainier where it was 63 degrees this afternoon at 5400 feet.
Tuesday will be similar to today with some highs in the 60s...mostly
sunny skies...and patchy morning fog.
The upper ridge will move east and weaken Tuesday night with
southwesterly flow aloft increasing off the coast. A weak weather
system will move onto the coast late Tuesday night and into the
interior Wednesday. Model solutions continue to be inconsistent with
the European model (ecmwf) and Canadian keeping this feature offshore while the NAM
and the GFS bring light rain into the area on Wednesday. As a
compromise have introduced low chance probability of precipitation over the interior for
Wednesday. Skies should be pretty cloudy as well.
Another impulse moves into the region Wednesday night or Thursday.
Have kept chance probability of precipitation over the whole area Wednesday night with
likely probability of precipitation over western sections by Thursday afternoon. High
temperatures will be mostly in the 50s Wednesday and Thursday under
cloudy skies. Burke
Long term...models generally have a wet looking system moving
through the region Thursday night through Friday night and the
forecast generally has likely probability of precipitation during this period. Another
system arrives around Sunday. Model timing is imprecise but the
extended period definitely looks like it has more normal weather
with clouds and rain. Highs will be mainly in the 50s. Except for a
brief period over the weekend...the snow level in the mountains will
be 7000 feet or higher. Burke
Hydrology...river flooding is unlikely over the next 7 days.
Aviation...flow aloft will become southerly late tonight and
Tuesday as an upper ridge over the area shifts east of the Cascades.
High pressure east of the Cascades combined with lower pressure offshore will
give low level offshore flow. The air mass is dry and stable. There
will be patchy shallow stratus and fog over the south interior late
tonight and Tuesday morning. Albrecht
Ksea...north wind 5 8 knots will shift to northeast 4-6 knots after
o4z then will shift to southeast 5-8 knots after 18z Tuesday. Expect good
visibilities with only thin cirrus through tonight. Albrecht
Marine...lower pressure over the offshore waters with high pressure east
of the Cascades will keep the flow easterly through Tuesday.
The surface high east of the Cascades will gradually weaken starting
on Tuesday. A weak warm front will move northeast through the
coastal waters on Wednesday. Another frontal system will stall in the
coastal waters Thursday and Friday then push inland on Sat.
Offshore flow will give Small Craft Advisory conditions to the West
Entrance to the Strait of Juan Delaware fuca and to the coastal waters
adjacent to the West Entrance. The winds will ease around noon on
Tuesday. A Small Craft Advisory for hazardous seas is in effect for the
remainder of the coastal marine zones tonight for a 10-11 feet swell
at 15 or 16 seconds. A Small Craft Advisory is in effect for rough
Grays Harbor bar conditions through tonight as well.
Frontal systems will affect mainly the coastal zones Wednesday-Friday with
Small Craft Advisory conditions there at times. Albrecht
Pz...Small Craft Advisory for hazardous seas until 3 am PST Tuesday
for coastal waters from Cape Flattery to James Island 10 to
60 nm-coastal waters from James Island to Point Grenville
10 to 60 nm-coastal waters from James Island to Point
Grenville out 10 nm-coastal waters from Point Grenville to
Cape Shoalwater 10 to 60 nm-coastal waters from Point
Grenville to Cape Shoalwater out 10 nm.
Small Craft Advisory for rough bar until 3 am PST Tuesday for
Grays Harbor bar.
Small Craft Advisory until 10 am PST Tuesday for coastal waters
from Cape Flattery to James Island out 10 nm-West Entrance
U.S. Waters Strait of Juan Delaware fuca.
An illustrated version of this forecast discussion can be seen at