Scientific Forecaster Discussion
fxus66 ksew 251542
Area forecast discussion
National Weather Service Seattle Washington
845 am PDT Sat Mar 25 2017
Synopsis...an upper level trough will move inland today. After
dry weather tonight a front will bring rain to western Washington
Sunday. A warm front will brush the area on Tuesday and then a
rather wet frontal system will reach the area on Wednesday.
Short term...today we will see scattered showers and sunbreaks.
Tonight will be dry under weak high pressure and offshore flow.
A front will spread rain onto the coast Sunday morning and into
the interior of western Washington by midday. The rain will turn
to showers later Sunday afternoon or early evening. A trough will
bring a second round of showers to the area Monday morning. Weak
high pressure will build into the area Monday night.
Long term...a frontal system will move slowly through the area
Tuesday and Wednesday. Tuesday does not look too wet--it is just a
brush by warm front and most of the rain GOES into British Columbia
during the day. That front sags south into western Washington
Tuesday evening, and the rain picks up, and then a surge of heavier
rain should arrive later Tuesday night through Wednesday. The front
moves inland Wednesday night, and then a cool upper trough will move
through the region on Thursday.
Aviation...a weak upper trough over western Washington this
morning will continue east inland this afternoon. Westerly flow
aloft over Washington. Air mass somewhat moist and unstable with
lingering showers ending today. The next Pacific weather system will
begin to spread mid and high level clouds onshore by Sunday morning.
Primarily VFR conditions through midday Sunday with areas of
lingering MVFR ceilings in clouds and showers ending by midday
today. Cloud banking up along the Cascades in the upslope westerly
flow for frequent mountain obscuration into this evening. Potential
for some patchy fog in the south sound area Sunday morning.
Ksea...the Olympics are shadowing the terminal area in the westerly
flow aloft for VFR conditions today. The shower threat with
associated MVFR ceilings confined mainly to the south and north of
the terminal. Southerly winds around 10 kt to continue through the
day today becoming more southeast overnight. Buehner
Marine...a weak ridge of higher pres over western Washington today
with light onshore flow will move east of the Cascades tonight. A
Pacific frontal system about 350 nm offshore is expected to approach
the coast tonight with offshore flow developing.
Gale force winds are possible in the offshore outer waters as this
frontal system approaches early Sunday. The front is expected to
move ashore late Sunday. The next frontal system is forecast to
arrive Tuesday with another on Wednesday. Buehner
Hydrology...river flooding is not expected for the next 7 days
with the exception of the flood prone Skokomish River in Mason
County where heavier rain in the Olympics Tuesday night and
Wednesday could be enough to get the river above flood stage.
Climate...with 0.24 inches yesterday the monthly precipitation
total for Seattle is now 6.11 inches. Combined with the 8.85
inches in February this is only the 3rd time since weather records
started in Seattle in the 1890's that both February and March have
gotten 6 inches plus of precipitation. The other two occurrences
2014 and 1972. Felton
Pz...Small Craft Advisory coastal waters from Cape Flattery to Cape
Shoalwater from 10 nm out to 60 nm.
Gale watch in effect for the coastal waters from Cape
Flattery to Cape Shoalwater from 10 nm out to 60 nm.