Alert archive / Washington / Mesoscale Discussions in 2021

Mesoscale Discussion 1933

November 9, 2021Clallam County, Grays Harbor County, Pacific County, Washington

The Storm Prediction Center issued this mesoscale discussion at Nov 9, 2021, 11:02 AM PST for Clallam County, Grays Harbor County, Pacific County, Washington. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Nov 9, 2021, 11:02 AM PST (19:02 UTC)
Expired: Nov 9, 2021, 1:30 PM PST
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 5%

Counties Clallam County, WA, Grays Harbor County, WA, Pacific County, WA

The radar

The Langley Hill radar (KLGX), 37 km from the middle of the area, began a volume at 19:01 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 12:00Z, 7.0 hours before the alert went out and 72 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: 599 m above ground
0-6 km bulk shear: 66 kt
0-1 km storm-relative helicity: 887 m²/s²
0-3 km storm-relative helicity: 1203 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

451 
ACUS11 KWNS 091902
SWOMCD
SPC MCD 091902 
WAZ000-092130-

Mesoscale Discussion 1933
NWS Storm Prediction Center Norman OK
0102 PM CST Tue Nov 09 2021

Areas affected...Coastal western Washington

Concerning...Severe potential...Watch unlikely 

Valid 091902Z - 092130Z

Probability of Watch Issuance...5 percent

SUMMARY...The potential exists for a thunderstorm-related strong
wind gust and/or a waterspout or brief tornado this afternoon in and
near coastal portions of Washington.

DISCUSSION...Visible satellite imagery indicates some increase and
deepening of low-topped convection through mid/late morning
offshore, with a corresponding uptick in isolated lightning flashes.
This is related to a steepening of lapse rates within the
post-frontal environment as a potent shortwave trough/jet streak
influences the region. Modest near-shore/coastal destabilization
will continue to occur amid cloud breaks. Bands of convection will
continue to move onshore through late morning, with additional and
potentially stronger/more cellular low-topped thunderstorms evolving
and spreading toward the coast/inland this afternoon. Supported by
35-45 kt southwesterly winds within the lowest 1-2 km AGL (per
KRTX/KATX WSR-88D VWP data), a convectively enhanced wind gust
and/or a waterspout or brief tornado could occur in coastal portions
of Washington through the afternoon.

..Guyer.. 11/09/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...SEW...PQR...

LAT...LON   48282383 47832363 46892326 46622360 46492394 46702434
            48342502 48282383

Nearby

Mesoscale Discussions in Washington, 2021 Every mesoscale discussion 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.