Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
300 PM PST Tuesday Dec 10 2013
Synopsis...an upper level ridge will move over the area Wednesday
for a dry day over most of the area...but a weak warm front could
bring a chance of rain to the north part. A Pacific cold front will
bring rain on Thursday. Another frontal system will reach the area
this weekend. Temperatures will be near normal.
Short term...most shower activity has ended though there is still
some over southern areas. Will keep chance of showers going over the
south this evening. Temperatures are still cold enough that high
elevations in the south could get a little snow in the showers. A
drying trend confines the shower chance to the mountains later
tonight. Overnight lows will be around freezing but the showers
should be over by the time the temperature gets that low.
So an Arctic outbreak has ended with hardly any interesting weather.
There was no big snowstorm...no big rain washing away the snow...no
flooding. Temperatures fell into the teens a couple of nights and
highs struggled to reach freezing for several days.
Wednesday will be mainly dry though a system moving into British
Columbia could brush the far north. Have chance probability of precipitation there that
continue Wednesday night. Should see some low 40s for highs on
Model timing for the Thursday system has not changed. Rain should
begin on the coast in the morning and spread inland in the
afternoon. The main part of the rain will probably be Thursday
evening. Highs over The Lowlands will be in the low to middle 40s. Snow
amounts in the mountains could reach advisory levels. Showers taper
Friday with highs in the middle 40s. Burke
Long term...next system arrives Saturday. GFS and Euro are in good
agreement. Models squeeze out a few hundredths during the day over
the interior as some sort of warm front moves north. The cold front
follows Saturday night and this feature has lost a lot of punch in
recent model runs. Have likely probability of precipitation coast and mountains with chance
probability of precipitation elsewhere. Showers follow Sunday and taper Monday. Temperatures
will be close to normal...highs in the middle 40s with lows around 40.
Hydrology...river flooding is not expected for the next 7 days.
Aviation...an upper level ridge offshore tonight will move over the
Pacific northwest on Wednesday. Light west-northwest winds becoming light southwesterly on
Wednesday. Stable conditions. Moist below 7k feet...drying on
Wednesday. Widespread low MVFR and local IFR ceilings through Wednesday
Ksea...precipitation is no longer expected. A MVFR or low VFR
stratus deck likely through the night with IFR ceilings possible late
tonight/early Wednesday morning for a few hours. Temperatures in the
middle/upper 30s through midnight...falling to 32-34 degrees for a low
Wednesday morning. Scattered ceilings above 3k feet expected by midday Wednesday.
Marine...light flow continues tonight and Wednesday with high pressure
inland and low pressure offshore. A front will bring small craft
winds to portions of the waters Thursday. Onshore flow Thursday
night...then lighter flow Friday as higher pressure builds over the
waters. A weak front will brush the waters over the weekend.
For the graphical afd...visit