Alert archive / Washington / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 3, NWS Seattle, WA

August 3, 2021King County, Snohomish County, Washington

NWS Seattle, WA issued this severe thunderstorm warning at Aug 3, 2021, 5:12 PM PDT for King County, Snohomish County, Washington. It was in force for 33 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 3, 2021, 5:12 PM PDT (00:12 UTC)
Expired: Aug 3, 2021, 5:45 PM PDT
In force: 33 min
Issued by: NWS Seattle, WA
Area: Storm-based polygon
Hail: 1.25 in
Wind: 50.0 mph

Counties King County, WA, Snohomish County, WA

The radar

The Seattle radar (KATX), 107 km from the middle of the area, began a volume at 00:13 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Quillayute State, WA (KUIL), launched 00:00Z, 0.2 hours before the alert went out and 244 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1439 m above ground
0-6 km bulk shear: 17 kt
0-1 km storm-relative helicity: -21 m²/s²
0-3 km storm-relative helicity: 43 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

385 
WUUS56 KSEW 040012
SVRSEW
WAC033-061-040045-
/O.NEW.KSEW.SV.W.0003.210804T0012Z-210804T0045Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Seattle WA
512 PM PDT Tue Aug 3 2021

The National Weather Service in Seattle has issued a

* Severe Thunderstorm Warning for...
  Southern Snohomish County in west central Washington...
  Northeastern King County in west central Washington...

* Until 545 PM PDT

* At 511 PM PDT, a severe thunderstorm was located near Snoqualmie
  Pass, moving north at 25 mph.

  HAZARD...Half dollar size hail. 

  SOURCE...Radar indicated. 

  IMPACT...Damage to vehicles is expected. 

* This severe thunderstorm will remain over mainly rural areas of 
  southern Snohomish and northeastern King Counties, and will cross 
  US-2 east of Skykomish at 515 to 525 PM.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Prepare immediately for large hail and deadly cloud to ground
lightning. Seek shelter inside a well-built structure. Stay away from
windows.

&&

LAT...LON 4762 12125 4764 12134 4783 12135 4781 12110
TIME...MOT...LOC 0011Z 189DEG 20KT 4748 12132 

HAIL...1.25IN
WIND...<50MPH
 
$$

1 follow-up statement

406 
WWUS56 KSEW 040045
SVSSEW

Severe Weather Statement
National Weather Service Seattle WA
545 PM PDT Tue Aug 3 2021

WAC033-061-040055-
/O.EXP.KSEW.SV.W.0003.000000T0000Z-210804T0045Z/
Snohomish-King-
545 PM PDT Tue Aug 3 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHERN SNOHOMISH AND
NORTHEASTERN KING COUNTIES HAS EXPIRED...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning has been allowed to expire.  However small
hail up to one half inch is still possible with this thunderstorm.

LAT...LON 4762 12125 4764 12134 4783 12135 4781 12110
TIME...MOT...LOC 0045Z 189DEG 20KT 4766 12128 

$$

Schneider

The office that day

Everything else NWS Seattle, WA issued on the same UTC day.

Issued	Product	Office	Lasted
Aug 3, 8:50 PM PDT	Small Craft Advisory	SEW	3 hr
Aug 4, 2:26 AM PDT	Small Craft Advisory	SEW	25 hr
Aug 4, 2:59 PM PDT	Gale Watch	SEW	12 hr

Nearby

Severe Thunderstorm Warnings in Washington, 2021 Every severe thunderstorm warning in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.