Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
340 am PDT Wednesday Oct 22 2014
Synopsis...a strong frontal system will move through western
Washington today. Heavy rain will fall in the Olympics and north
Cascades. The rain will turn to showers tonight and Thursday.
Another low pressure system will reach the area late in the week.
Short term...a High Wind Warning is in effect for the San Juans and
western Whatcom this morning for south winds gusting to 60 miles per hour. This
high wind is caused by a tight surface low passing into southern
British Columbia. South winds will ease by middle morning.
The first wave of heavy rain continues to pass through western Washington
this morning. Three inches fell over the north coast with 2-4 in the
Olympics. This band will shift east into the interior and Cascades
this morning...with heavy rain ending over the Olympics. It looks
like the second wave of heavy rain will shift south...clipping the
central and south Cascades tonight. It looks like 1-3 inches are
expected in the Cascades...but overall rain amounts are less in the
Cascades compared to previous model solutions. This front has been
pretty progressive and this lessens the threat for river flooding.
As for the interior...expect rain at times through tonight with 1-2
inches of rain. Temperatures near 60 degrees this afternoon.
Moist southwest flow will continue Thursday and Thursday night for
more showers across the region. But heavy rains are not expected.
Probability of precipitation were raised as we should see off-and-on showers throughout much
of the day.
We may see a brief break in the weather Friday morning...then more rain
will spread north into western Washington Friday afternoon and evening.
Expect more wet and windy weather on Saturday. The main impact will
be the wind and the tracking of a surface low off the Washington coast.
Models bring a 980s mb low into western Washington Sat afternoon with high
wind possible...especially along the coast. Strong winds may also
occur in the interior as this system moves inland Sat night. Will
need to watch this system more closely as it evolves. 33
Long term...the air mass will remain cool and unstable on Sunday as
an upper level trough moves inland. A ridge will then pass overhead
on Monday for a break in the weather...will likely see probability of precipitation decreased
over this period. Then more rain and blustery weather by Tuesday as
another wet Pacific frontal system moves in. 33
Hydrology...a Flood Warning is in effect for the Skokomish River in
Mason County. The river is rising and is expected to reach minor
flood stage this morning.
Heavy rain will fall in the Cascades this morning and afternoon with
1-3 inches expected. But overall precipitation amounts are less compared to
previous solutions. Expect sharp rises on the rivers...but it
appears flooding is unlikely.
Aviation...a 995 mb surface low tracking NE over central Vancouver
Island will drag a front through western Washington this morning. This system
will bring strong flow aloft to western Washington...becoming light to moderate
SW flow tonight. Moist and generally stable. Rain at times. Ceilings
mostly VFR but occasionally MVFR with heavier precipitation.
Ksea...southerly winds 12-15 west/ gusts 25-30 knots...easing later this
morning. Rain at times. Ceilings mostly VFR above 3k feet. Visible 4-5 sm at
times during heavier precipitation.
Marine...strong southeast pressure gradients will produce high end gale
force winds over the coastal waters...entrances to the Strait...and
inland waters north of Puget Sound sound early this morning. Small craft winds
to 30 knots are expected in Puget Sound sound/central Strait...continuing
into the afternoon in Puget Sound sound. Winds will ease first along the
coast after 5-6 am...then across the interior after 8-9 am. Seas
over 15 feet are also expected today along with rough bar
There will be a relative lull in the stormy weather in the middle of
the week...then another strong weather system will affect the waters
Friday and Saturday. A deep surface low is expected to track through
the waters during this time but there is still a lot of uncertainty
with how strong the low will be and where it will go. Dtm
Washington...High Wind Warning San Juans and western Whatcom until 9 am this
Wind Advisory coast until 8 am this morning.
Wind Advisory western Skagit and Admiralty Inlet until 9 am
Flood Watch Mason County.
Pz...Gale Warning coastal waters...entrances to the Strait of Juan
Delaware fuca...northern inland waters...and Admiralty Inlet.
.Small Craft Advisory central Strait of Juan Delaware fuca and Puget Sound
sound and Hood Canal.
.Small Craft Advisory for rough Grays Harbor bar.
You can see an illustrated version of this forecast discussion at