Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
915 am PST Thursday Jan 29 2015
Synopsis...an upper ridge will provide dry and mild weather today
through Saturday. A front will bring rain back to the area Sunday
and early next week.
Short term...an upper level ridge over the Pacific northwest will lead to dry
and mild weather across western Washington today through Saturday. Skies
will be partly to mostly sunny with temperatures above normal -
highs in the 50s today and Friday. A warm front will move into b.C. On
Saturday which may clip the area for a few more clouds. But could
see highs in the low 60s again Saturday afternoon. The current
forecast is on track. 33
Long term...previous discussion...next frontal system still timed
into the area late Sunday although the 00z model runs were a touch
slower with the onset of the precipitation Sunday versus the
previous runs. Took the probability of precipitation out of 00z-06z Sunday time frame and
lowered the probability of precipitation for 06z-12z Sunday. This system is weak and not
expected to be much of a rain producer with just a few hundredths.
Model solutions start to diverge a bit for Monday with the European model (ecmwf)
bringing a stronger system into the area while the GFS brings a
weaker system into western Washington. With both models indicating
at least some light rain will stay with the rain likely forecast on
Monday. Model solutions continue to diverge Tuesday into Wednesday
with the GFS building a ridge over western Washington on Tuesday
keeping the weather dry while the European model (ecmwf) has a warm front
approaching...close enough to keep a chance of rain in the forecast.
The European model (ecmwf) brings the warm front into western Washington Tuesday
night and stalls the front over the area on Wednesday with a bit of
atmospheric river scenario setting up with the bulk of the
precipitation aimed at Vancouver Island. The GFS is more progressive
with the pattern with the warm front brushing western Washington
Tuesday night into Wednesday and a cold front moving through
Wednesday night. GFS ensembles area all over the place Tuesday into
Wednesday not lending much confidence in the model solution. With
the lack of consistency in the models and the scrambled ensembles
will stay with the chance probability of precipitation forecast for Monday night through
Wednesday. High temperatures will remain near or slightly above
normal through the period. Felton
Hydrology...flooding is not expected for the next 7 days.
Aviation...a weak upper level ridge will remain over western
Washington today and tonight. At the surface northerly and offshore
flow will continue. Satellite imagery shows fog/stratus over the
southwest interior and in the Strait but skies are mostly clear
elsewhere. All areas should be sunny in the afternoon.
Ksea...VFR conditions with just some thin high clouds this morning.
Northerly wind 7-11 knots. Chb
Marine...a surface ridge centered over eastern Washington will
maintain weak offshore flow through Saturday. Pressure gradients
across western Washington will remain weak...producing northeast
winds along the coast and through Puget Sound sound...and easterly winds
through the Strait. Winds are forecast to remain less than 20 knots
except for the West Entrance where a Small Craft Advisory for 15-25
knots winds is in effect this morning. Winds could reach advisory level
there from time to time through Saturday.
Models bring a front across the area Sunday. Recent models have
trended weaker with the front and are keeping winds below 20 knots. A
stronger system will follow on Monday but models are waffling about
its strength. The current forecast keeps winds on the light side. Chb
Pz...Small Craft Advisory West Entrance.
You can see an illustrated version of this forecast discussion at