Severe Thunderstorm Warning 2, NWS Seattle, WA

Area Forecast Discussion
National Weather Service Seattle WA
310 AM PDT Sat May 30 2020

.SYNOPSIS...An upper level low pressure system moving up from the
south will move through the area later today into early Sunday for
widespread showers across the region and possible thunderstorms
over the Cascades. Drier conditions return early next week as
weak high pressure builds into the region. The unsettled pattern
looks to return by Wednesday and Thursday of next week.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...High and mid level clouds
continue to stream across the region this morning in advance of an
upper level low pressure moving northward over northern
California. Shower activity will gradually ramp up through the day
with widespread showers leading to a fairly wet afternoon and
evening ahead. The best instability remains destined for points
east of the Cascade crest, but there's enough to warrant
mentioning a slight chance of thunder in the Cascades from this
morning into this evening. All of the shower activity combined
with increasing low level onshore flow spells a significant cool
down with high temperatures across much of the interior of Western
Washington 10 to 20 degrees cooler than yesterday. Showers will
continue through tonight then gradually taper off Sunday as the
upper low lifts northward out of the region. Weak, fairly
nondescript upper troughing remains over the area on Monday. With
onshore flow continuing, this will limit high temperatures to
about seasonal normals and likely keep some cloud cover around
into midday.

.LONG TERM /TUESDAY THROUGH FRIDAY/...Weak upper ridging builds
into the region on Tuesday. Temperatures will warm a few degrees
to just above normal with more sunshine. The ridge flattens pretty
quickly by Wednesday as a weak system slides by just to our
north. This ushers in a return to a more unsettled period that is
likely to stick around for the second half of the week. As strong
ridging builds over the midsection of the country Thursday and
beyond, this favors a mean trough position over the Pacific
Northwest.    27

&&

.AVIATION...A vigorous upper short wave will move up from the
south today and through the area tonight in southerly flow aloft.
At the surface, onshore flow today will increase tonight. Stable
air early today will become unstable later today, especially over
the Cascades. There will be mostly mid and high clouds most of the
day today with some patchy low clouds near the coast. Low and mid
level moisture will increase late this afternoon and evening with
MVFR or IFR ceilings developing most areas.

KSEA...Mid and high clouds today. Ceilings will gradually lower
this afternoon with low clouds developing this evening. There is a
small threat of thunder later this afternoon and evening but it is
too low to mention in the TAF. Northerly wind 5-10 knots will
become southerly 10-15 knots early this evening. Schneider

&&

.MARINE...Onshore flow today will bring small craft advisory
strength westerly winds to the Coastal Waters, the Strait of Juan
de Fuca, and Admiralty Inlet.

A weather system will move up from the southwest this afternoon
and evening. There will be a burst of stronger onshore flow behind
this system tonight with gale force west winds in the Strait and
small craft advisory strength winds all other waters.

A more modest onshore flow pattern will set up on Sunday and
continue through the middle of next week. This pattern favors
small craft advisory strength west winds for the central and
eastern Strait of Juan de Fuca each evening.

A weak frontal system will brush the area later Tuesday but it
does not look like it will have much impact. Schneider

&&

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

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 11 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 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 10 Nm.

     Small Craft Advisory until 5 PM PDT this afternoon for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning from 5 PM this afternoon to 5 AM PDT Sunday for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 5 PM this afternoon to 5 PM PDT Sunday
     for Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory from 2 PM this afternoon to 11 AM PDT
     Sunday for West Entrance U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory until 5 AM PDT Sunday for Admiralty Inlet.

     Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Sunday
     for Puget Sound and Hood Canal.

&&

www.weather.gov/seattle

Special Weather Statement
National Weather Service Seattle WA
724 AM PDT Sat May 30 2020

WAZ555-568-569-301500-
West Slopes North Central Cascades and Passes-West Slopes South
Central Cascades and Passes-East Puget Sound Lowlands-
724 AM PDT Sat May 30 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL KING AND
NORTHEASTERN PIERCE COUNTIES UNTIL 800 AM PDT...

At 723 AM PDT, Doppler radar was tracking a strong thunderstorm 13
miles east of Enumclaw, or 19 miles south of North Bend, moving north
at 40 mph.

Dime size hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Greenwater.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4714 12157 4715 12180 4737 12184 4737 12151
TIME...MOT...LOC 1423Z 178DEG 34KT 4722 12171

Kovacik

Special Weather Statement
National Weather Service Seattle WA
726 AM PDT Sat May 30 2020

WAZ555-569-301500-
West Slopes South Central Cascades and Passes-East Puget Sound
Lowlands-
726 AM PDT Sat May 30 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL PIERCE COUNTY UNTIL
800 AM PDT...

At 726 AM PDT, Doppler radar was tracking a strong thunderstorm 10
miles west of Mount Rainier, or 23 miles northwest of Packwood,
moving north at 35 mph.

Dime size hail and winds in excess of 30 mph will be possible with
this storm.

This storm will remain over mainly rural areas of south central
Pierce County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4684 12188 4680 12202 4698 12219 4705 12189
TIME...MOT...LOC 1426Z 161DEG 31KT 4688 12199

Kovacik