Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
916 PM PST Wednesday Dec 11 2013
Synopsis...high pressure over the area will continue moving
east...allowing a low pressure system to approach the coast on
Thursday. Look for this system to move across the area Thursday
evening. High pressure aloft will return on Friday but the air
mass will remain moist and there will be enough lift for a
chance of precipitation. Another system will approach the region
an upper ridge presently over the region will continue moving
east...allowing an upper trough and associated cold front over the
northeast Pacific to approach the region during the day Thursday. The
upper trough will move across the County Warning Area Thursday evening. The weakening
cold front might dissipate as it moves onshore Thursday evening.
Expect an upper ridge to move over the Pacific northwest in the
wake of the system on Thursday. Weak warm air advection will probably
result in some spotty light precipitation during the day. The ridge will
weaken Friday night and even more Saturday morning. There is a chance
that much of Friday night through Saturday morning may end up dry for
much of the County Warning Area. The next upper trough should begin affecting the
region Saturday afternoon.
Long term after the previous discussion...
after the rain event ends Saturday night...showers follow on Sunday.
Monday could be dry but kept low chance probability of precipitation. Another system will
arrive from the northwest on Tuesday and have probability of precipitation ramping up a
bit then. A few model runs have been showing the return of Arctic
air from Canada around the middle of next week. Currently both the
GFS and the Euro shove the bulk of the cold air far to the east
but do bring some modified Arctic air into the northernmost zones
at least. Burke
river flooding is not expected for the next 7 days.
Aviation...southwest flow aloft will become westerly on Thursday as
an upper trough moves over the area. A frontal system will move
onshore later Thursday. Air mass stable with high level moisture and
areas of low level coast and southwest interior. Becoming moist all
levels all areas Thursday as the front moves onshore.
Areas of low clouds and fog over the coast and southwest interior
tonight but high clouds should keep this stuff from becoming too
Ksea...high clouds tonight. There is a chance some fog or very low
clouds to the south could spread up to the terminal tonight but the
threat does not seem high enough to mention in the taf. Low clouds
and rain will develop early in the afternoon Thursday as a front
moves onshore. Light wind will become southeast 3-6 knots later
tonight and Thursday morning...then south 6-10 knots Thursday
Marine...a frontal system will bring Small Craft Advisory southerly
winds to most waters Thursday. Weak high pressure will move over
the area on Friday. Southerly winds will increase again Saturday as
another front moves through. Schneider
Pz...small craft advisories are in effect for the coastal waters
and West Entrance to the Juan Delaware fuca until 6 PM Thursday.
Small Craft Advisory in effect from 6 am Thursday to midnight Thursday
night for the East Entrance to the Strait of Juan Delaware fuca...
northern inland waters...and Admiralty Inlet.
For the graphical afd...visit