Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 222234
Area Forecast Discussion
National Weather Service Seattle WA
334 PM PDT Sat Oct 22 2016
.SYNOPSIS...A series of fronts will move through the area over the
next week for rain at times. Wednesday in particular looks wet
.SHORT TERM...A fairly weak front will bring a little rain to the
coast this evening. The front falls apart as it moves inland and
the interior will probably not see much more than spotty rain.
Sunday will be in between weather systems. Southwest flow aloft
will veer to southerly as an upper low digs offshore. This will
bring increasingly moist flow aloft to Western Washington and
perhaps even shift the weak frontal boundary back over area.
The offshore upper low will push a weakening front across the area
on Monday. Rain will become likely but the system looks pretty
Tuesday will be in between fronts again but moist southwest flow
aloft will keep a chance of showers in the forecast with higher
chances on the coast. A deep surface around 970 mb - will track
south to north well offshore and tighten surface gradients across
the area for some breezy to windy conditions coast and north
.LONG TERM...Models are in pretty good agreement showing a warm
front moving up from the southwest and through Western Washington
on Wednesday. It looks like a good soaker. There will also be a
surface low around 990 mb passing offshore and into Vancouver
Island. This should keeps things breezy to windy coast and north
interior although models differ on how close the low will get
which would affect how much wind occurs.
Models begin to diverge Thursday and there is little agreement
after that other than the general idea of additional frontal
systems keeping things wet at times. Schneider
.AVIATION...An upper trough will persist around 130W-140W for the
next 24 hours, with moderate S-SW flow aloft over western
Washington. A surface low moving northward well off the coast
this afternoon will maintain drying easterly surface flow until
a weakening front moves onto the coast before sunrise Sunday. The
dying front will first spread a few showers onto the coast around
03z (8 pm), with showers withering away by the time they reach
the I-5 corridor before sunrise Sunday. IFR conditions should be
confined to the coast. The I-5 corridor should still experience
enough drying easterly surface flow and mid-level clouds tonight
to inhibit fog development and maintain mostly VFR cigs.
KSEA...A drying easterly component to the low-level flow will keep
VFR cigs for the next 30 hours. A dying front should bring a few
sprinkles to the terminal in the 10z-14z time frame, but even
that should not be enough to lower cigs below about 040.
.MARINE...A strengthening 998 mb low will move due north along
130W tonight, on its way to Haida Gwaii on Sunday morning. A
trailing front will slowly move onshore early Sunday morning and
then dissipate over the inland waters on Sunday afternoon.
Dissipation of the front will lead to a lull in the wind on Sunday
afternoon. An even stronger 970 mb low will slowly move northward
near 130W and west of Washington on Monday afternoon and Monday
night, bringing Gales to the coastal waters. Yet another strong
low center will move northward along 130W on Wednesday. Haner
.HYDROLOGY...River flooding is not expected for the next seven
PZ...Small Craft Advisory until 5 AM PDT Sunday for Coastal Waters
From Cape Flattery To James Island 10 To 60 Nm-Coastal
Waters From Cape Flattery To James Island Out 10 Nm-Coastal
Waters From James Island To Point Grenville 10 To 60 Nm-
Coastal Waters From Point Grenville To Cape Shoalwater 10
To 60 Nm-West Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory for rough bar until 4 PM PDT this afternoon
for Grays Harbor Bar.
Small Craft Advisory from 6 PM this evening to 5 AM PDT Sunday
for Coastal Waters From James Island To Point Grenville Out
10 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm.
Small Craft Advisory for hazardous seas until 3 PM PDT this
afternoon for Coastal Waters From James Island To Point
Grenville Out 10 Nm-Coastal Waters From Point Grenville To
Cape Shoalwater Out 10 Nm.
Small Craft Advisory from 2 AM to 2 PM PDT Sunday for East
Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland
Waters Including The San Juan Islands.
You can see an illustrated version of this discussion at