Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
300 PM PST Thursday Feb 26 2015
Synopsis...a weak weather system will produce scattered showers
across western Washington through Friday...especially at the coast
and in the southwest. A few inches of snow will fall in the
mountains. An upper ridge and offshore flow will bring sunny days
and cool nights this weekend. A weak system will move through Sunday
night and Monday...with dry weather again Tuesday and Wednesday.
Short term...an upper level closed low will move south along the
coast tonight and into Oregon Friday. This will bring showers to the
area with more numerous showers along the coast and in the Olympics.
There is a chance of thunderstorms along the coast late tonight and
Friday. By Friday afternoon the shower chance will be decreasing
especially over the north. Highs Friday will be in the low 50s.
There will be some snow in the Olympics and southern part of the
Cascades. Amounts will probably be up to six inches over higher
terrain. The avalanche unit thinks it could be up to eight inches
and that a Snow Advisory might be needed...but will leave that up to
Cold dry air will begin to spill out of British Columbia into
western Washington Friday night. Skies will clear from north to
south on Friday night and Saturday. By Saturday afternoon skies will
be clear. Breezy conditions will be common as the cold air advances.
The north interior could be windy at times. Highs on Saturday will
be a few degrees lower than Friday...with not much afternoon heating
as cold air moves over the area.
On Sunday the cool dry air mass will remain over the area. Overnight
lows both Saturday night and Sunday night will be in the 30s with
sheltered locations likely to fall below freezing. Burke
Long term...a weak weather system will bring a chance of rain
Sunday night through Monday night. The strength of this system has
been waning in recent model runs. Tuesday through Thursday is likely
to be a dry period...with a chance of rain returning Friday. Highs
and lows will be slightly below normal. Burke
Hydrology...flooding is unlikely for the next 7 days.
Aviation...a low pressure system moving southeast from the b.C.
Coastal waters will bring showers to western Washington tonight. Northerly
flow will develop Friday afternoon and evening as the low moves
south and high pressure builds over British Columbia. The air will
be moist and become unstable overnight...then dry and stabilize late
Friday with clearing Friday night.
Ksea...showers will increase tonight as a weather system moves
through the area. Light and variable winds will become northerly and
Marine...a weak frontal system and low pressure area will move from
the b.C. Coastal waters southeast through western Washington tonight. Pressure
gradients are expected to remain light over the waters through early
Friday. High pressure will build over the interior of British Columbia Friday
and Friday night and as the low moves south out of the area north to NE
flow will increase later Friday. Small Craft Advisory conditions are
likely over most of the waters starting around Friday afternoon through
about Sat morning. High pressure will move over the waters Sunday giving
light winds. Another low will drop southeast across the area Sun
night and Monday...followed again by NE winds as high pressure
builds over b.C. Monday and Tuesday.
You can see an illustrated version of the forecast discussion at