Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 290401
Area Forecast Discussion
National Weather Service Seattle WA
900 PM PDT THU JUL 28 2016
.SYNOPSIS...Upper level ridging and weak low level onshore flow will
linger one more day over Western Washington resulting in a warm and
sunny day for Friday. An upper level trough passing to the north of
the area Saturday and Sunday will bring cooler temperatures to the
area through the weekend. A stronger upper level trough will arrive
Monday night bringing a chance of showers to the area and possibly
thunderstorms to the crest of the Cascades. Sunny skies and higher
temperatures will return mid week.
.SHORT TERM...Marine stratus burned back to a few spots along the
central and southern Washington coast this evening. Moderate low
level onshore gradients will help stratus work back into parts of
the interior by early Friday morning. Expect low clouds and fog
similar to this morning, reaching Shelton and likely into the East
Strait. Like this morning, the stratus should burn quickly back to
the coast with sunny and warm conditions. The approaching upper
level trough over northern British Columbia will help dampen heights
over Washington, which will lower limit high temperatures a bit.
In addition, increasing low level onshore flow will also help keep
temperatures cooler, especially along the coast where highs will
run 5-10 degrees cooler than Thursday.
The stronger onshore flow Friday night will spread marine stratus
farther inland by Saturday morning, while upper level heights will
continue to fall as the weak upper level trough works further south
into British Columbia. This will definitely result in a much
coolerday Saturday with highs in the 7This will give a considerably
cooler day Saturday0s inland and 60s on the coast. Expect afternoon
clearing over the interior with some sunshine. Onshore flow will
persist Saturday night into Sunday, keeping the marine layer in
place through much of the interior Sunday morning. Short wave
ridging will help clear skies out during the day and high
temperatures a few degrees warmer than Saturday.
.LONG TERM...from previous discussion...An upper level low will
approach the coast Sunday night and move inland Monday. This will
bring a chance of showers to most areas. There is some divergence
aloft so have introduced a chance of thunderstorms to the north
Cascades on Monday afternoon and evening.
Heights rebuild after the low passes for a lower chance of showers
on Tuesday and dry conditions Wednesday and Thursday. Temperatures
will be a few degrees either side of normal during this period. Burke
.AVIATION...Dry stable air except for shallow coastal marine
stratus and fog patches there. The marine air did not intrude much
Thursday morning and Friday morning should be about the same with
the areas of low clouds and fog patches mainly up to about Shelton
and perhaps a few patches around Whidbey Island again.
KSEA...Clear skies, north breeze.
.MARINE...High pressure is offshore with lower pressure over
land and especially east of the Cascades. Onshore flow will increase
through the end of the week as an upper level trough moves into the
area. The forecast has stronger northwest winds developing over the
northwest part of the Coastal waters and there is a gale watch for
that for late Friday, and there is also a gale watch for the Strait
for when the strong westerly push develops.
PZ...Small Craft Advisory until 3 AM PDT Saturday for Coastal Waters
From Cape Flattery To James Island Out 10 Nm-Coastal Waters
From James Island To Point Grenville Out 10 Nm-Coastal
Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-
Coastal Waters From Point Grenville To Cape Shoalwater Out
Gale Watch from Friday afternoon through Saturday afternoon for
Coastal Waters From Cape Flattery To James Island 10 To 60
Nm-Coastal Waters From James Island To Point Grenville 10
To 60 Nm.
Small Craft Advisory until 5 PM PDT Friday for Coastal Waters
From Cape Flattery To James Island 10 To 60 Nm-Coastal
Waters From James Island To Point Grenville 10 To 60 Nm.
Gale Watch from Friday afternoon through late Friday night for
Central U.S. Waters Strait Of Juan De Fuca-East Entrance
U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory until 2 AM PDT Friday for Central U.S.
Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
Strait Of Juan De Fuca.
You can see an illustrated version of this discussion at