Alert archive / Louisiana / Mesoscale Discussions in 2021

Mesoscale Discussion 737

May 25, 20217 parishes in Louisiana

The Storm Prediction Center issued this mesoscale discussion at May 25, 2021, 4:40 PM CDT for 7 parishes in Louisiana. It was in force for 65 min.

The area

The outline as issued.

The facts

Issued
May 25, 2021, 4:40 PM CDT (21:40 UTC)
Expired
May 25, 2021, 5:45 PM CDT
In force
65 min
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch unlikely
Chance of a watch
20%

Counties Bienville Parish, LA, Bossier Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Lincoln Parish, LA, Red River Parish, LA, Webster Parish, LA

The radar

The Shreveport radar (KSHV), 60 km from the middle of the area, began a volume at 21:39 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

Shreveport, LA (KSHV), launched 12:00Z, 9.7 hours before the alert went out and 52 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, Shreveport, LA at 12:00Z on 2021-05-25Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 12 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, Shreveport, LA at 12:00Z on 2021-05-25The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 75 square meters per square second.1939Sfc1 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
12 J/kg
Mixed-layer CIN
-179 J/kg
Mixed-layer LCL
1121 m above ground
0-6 km bulk shear
18 kt
0-1 km storm-relative helicity
75 m²/s²
0-3 km storm-relative helicity
79 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

968 
ACUS11 KWNS 252140
SWOMCD
SPC MCD 252140 
LAZ000-252245-

Mesoscale Discussion 0737
NWS Storm Prediction Center Norman OK
0440 PM CDT Tue May 25 2021

Areas affected...Northern Louisiana

Concerning...Severe potential...Watch unlikely 

Valid 252140Z - 252245Z

Probability of Watch Issuance...20 percent

SUMMARY...A strong to near-severe gust (35-45 kts) possible with a
small bowing segment now east of Shreveport. Decreasing shear
downstream will likely mean the activity becomes more disorganized
with time.

DISCUSSION...KSHV VAD profiles show around 50-60 kts at around 2-3
km within the last 30-45 minutes with the passage of a small bowing
segment. Buoyancy and low-level lapse rates just downstream of this
activity are sufficient for a strong to perhaps near-severe wind
gust (35-45 kts) over the next 1-2 hours. Shear, both deep-layer and
low-level, are not overly strong. This activity probably will begin
to become more disorganized beyond that 1-2 hour time frame.

..Wendt/Edwards.. 05/25/2021

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

ATTN...WFO...SHV...

LAT...LON   32289265 31929331 31879364 31999393 32259392 32719387
            32969363 33009301 33019277 32799243 32449255 32289265

Nearby

Mesoscale Discussions in Louisiana, 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.