Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 071017

Area Forecast Discussion
National Weather Service Seattle WA
317 AM PDT Fri May 7 2021

.SYNOPSIS...An upper trough will move through the area today with
a cool air mass, onshore flow, and showers. Isolated
thunderstorms are possible. A weak weather system will brush the
area over the weekend before high pressure builds for the first
half of next week.


.SHORT TERM /TODAY THROUGH SUNDAY/...An upper trough will bring
showers today with a Puget Sound Convergence Zone over Snohomish
County sagging south into King County. There will also be a slight
chance of thunderstorms this afternoon with the added lift from
daytime heating. The mountains will pick up a few inches of snow
with snow levels 3000-3500 feet but impactful accumulations are
not expected in the passes. Highs will be in the 50s which is
several degrees below normal.

The upper trough will shift inland tonight with showers becoming
mostly confined to the Cascades and a lingering PSCZ over King
County. A couple of weather disturbances in the west to northwest
flow aloft will maintain a chance of showers this weekend. Highs
in the 50s on Saturday will inc up a few degrees on Sunday but
still be slightly below normal. Schneider

.LONG TERM /MONDAY THROUGH THURSDAY/...An upper ridge will bring
dry and warmer weather for the first half of next week. Highs will
warm to near 70 from Seattle south by Tuesday with 60s elsewhere.
A weak weather system could brush the area to the north in the
middle of the week for a few showers but mostly it will remain dry
with highs slightly above normal. Schneider


.AVIATION...Cool upper level trough over the area today will shift
into Eastern Washington tonight. Light flow aloft becoming
northwesterly tonight and Saturday. Onshore flow in the lower
levels through the weekend.

Air mass slightly unstable today with shower activity increasing
late morning into the afternoon hours. Ceilings with the showers
around 2000 feet. Outside of the shower activity ceilings
3500-4500 feet. Convergence zone in Snohomish county this morning
will sag south into Southern King and Northern Pierce county by
late this afternoon. The convergence zone will dissipate tonight.

KSEA...VFR ceilings this morning lowering down to around 2000 feet
this afternoon as convergence zone moves past the terminal.
Ceilings improving back up to 4000-5000 feet tonight. Winds
southerly 8 to 12 knots becoming northwest 22z-00z. Winds
switching back around to southerly after 07z tonight. Felton


.MARINE...Varying degrees of onshore flow will continue into the
first part of next week with high pressure over the coastal

Strongest onshore flow in the forecast period expected tonight
with gale warnings for the Central and Eastern Strait of Juan de
Fuca and small craft advisories for the adjacent inland waters.
Small craft advisory westerlies are possible Saturday evening in
the Central and Eastern Strait of Juan de Fuca. Felton


.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.


PZ...Small Craft Advisory from 2 PM this afternoon to 6 PM PDT this
     evening for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

     Gale Warning from 6 PM this evening to 6 AM PDT Saturday for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 6 PM this evening to 2 AM PDT Saturday
     for Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory from 6 PM this evening to 6 AM PDT Saturday
     for Admiralty Inlet.


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