Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
900 am PST Friday Mar 6 2015
Synopsis...an upper ridge will remain over the Pacific northwest
through Monday night...and western Washington will have more sunny
warm days and mostly clear nights. The ridge will weaken on
Tuesday...and a weak frontal system will probably bring some rain to
the area Tuesday night through Thursday.
Short term...an upper level ridge will continue to build just off
the Pacific northwest coast today...with light northerly offshore
flow at the surface. The high clouds over western Washington this
morning...associated with a weak upper system moving over the north
side of the upper ridge...should gradually clear out during the day.
Temperatures at 8 am were mainly in the middle 30s to middle 40s...and the
highs today should be 55 to 65.
The upper ridge will continue to build as it shifts westward tonight
and Saturday. As a result the flow aloft over western Washington
will veer to northwest...and weak northwesterly onshore flow will
develop at low levels. The upper ridge will weaken slightly and
shift toward the Pacific northwest coast again Saturday night and
Sunday. These are rather subtle changes. On the whole they will have
little effect...with more sunny warm days through the weekend.
Long term...here is the long term section from the early morning
forecast discussion -- a transition back to more normal March
conditions will begin on Tuesday. Model consensus for Tuesday is for
a chance of rain...mainly coast and later in the day. The latest 3
runs of the GFS have trended toward the European model (ecmwf) in showing a southern
stream system approaching the area from the southwest Tuesday night into
Thursday resulting in high chance to likely probability of precipitation and high temperatures
falling back into the middle and upper 50s. The air mass will likely be
rather warm across the area by midweek with low temperatures holding
in the middle and upper 40s across the area. Albrecht
Hydrology...flooding is unlikely for the next 7 days.
Aviation...an upper ridge will remain over the Pacific northwest
with west to northwest flow aloft. Air mass is stable with high
level moisture. At the surface...weak high pressure over western Washington
today will shift offshore tonight and Saturday.
Ksea...high clouds. Light wind becoming north to northwest 3-6 knots
this afternoon. Schneider
Marine...weak high pressure over the waters today will shift
offshore Saturday with a weak trough along the West Coast. The
trough will shift into eastern Washington Sunday and Monday. The
offshore high will shift inland Tuesday as a front approaches from
the west. Schneider
You can see an illustrated version of this forecast discussion at