Alert archive / Washington / Mesoscale Discussions in 2021

Mesoscale Discussion 1898

October 24, 2021Clatsop County, Oregon; Grays Harbor County, Pacific County, Washington

The Storm Prediction Center issued this mesoscale discussion at Oct 24, 2021, 9:58 PM PDT for Clatsop County, Oregon; Grays Harbor County, Pacific County, Washington. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Oct 24, 2021, 9:58 PM PDT (04:58 UTC)
Expired
Oct 25, 2021, 12:00 AM PDT
In force
2 hr
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch unlikely
Chance of a watch
5%

Counties Clatsop County, OR, Grays Harbor County, WA, Pacific County, WA

The radar

The Langley Hill radar (KLGX), 54 km from the middle of the area, began a volume at 05:03 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, 5.0 hours before the alert went out and 151 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-pSkew-T log-p diagram, Quillayute State, WA at 00:00Z on 2021-10-25Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 35 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Quillayute State, WA at 00:00Z on 2021-10-25The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 412 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
35 J/kg
Mixed-layer CIN
-7 J/kg
Mixed-layer LCL
737 m above ground
0-6 km bulk shear
33 kt
0-1 km storm-relative helicity
412 m²/s²
0-3 km storm-relative helicity
565 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

051 
ACUS11 KWNS 250459
SWOMCD
SPC MCD 250458 
WAZ000-ORZ000-250700-

Mesoscale Discussion 1898
NWS Storm Prediction Center Norman OK
1158 PM CDT Sun Oct 24 2021

Areas affected...Central/Southern WA Coast...Far Northern OR Coast

Concerning...Severe potential...Watch unlikely 

Valid 250458Z - 250700Z

Probability of Watch Issuance...5 percent

SUMMARY...A brief tornado or two may occur within the immediate
coastal regions of central/southern WA and northern OR. A strong
convectively added wind gust or two is also possible.

DISCUSSION...Recent radar imagery has shown several deeper cores
within the more cellular activity off the coast. Moderate low-level
rotation has been noted within a few of these cells. Buoyancy is
expected to remain very limited, but strong forcing for ascent will
persist and shear will remain very strong. Recent LGX VAD profiles
sampled over 50 kt of 0-1 km vertical shear and over 400 m2/s2 of
0-1 km storm-relative helicity. The conditions will continue to
support transient, low-topped convective cells with occasional
rotation. Isolated convectively augmented wind gusts and/or brief
tornado may occur in the immediate coastal regions of
central/southern WA and northern OR.

..Mosier/Hart.. 10/25/2021

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

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

LAT...LON   46722417 47402437 47472390 46792375 45742361 45592402
            46722417

Nearby

Mesoscale Discussions in Washington, 2021Mesoscale Discussions in Oregon, 2021Every 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.