Mesoscale Discussion 280

Issued

Mar 27, 2021, 2:16 PM CDT (19:16 UTC)

Expired

Mar 27, 2021, 3:45 PM CDT

In force

89 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...tornado watch likely

Chance of a watch

80%

The Shreveport radar (KSHV), 119 km from the middle of the area, began a volume at 19:16 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.

• Tornado Watch 60Mar 27, 3:20 PM CDT

832 
ACUS11 KWNS 271917
SWOMCD
SPC MCD 271916 
ARZ000-LAZ000-TXZ000-272045-

Mesoscale Discussion 0280
NWS Storm Prediction Center Norman OK
0216 PM CDT Sat Mar 27 2021

Areas affected...Portions of northeast TX...northern LA...and much
of southern/central/eastern AR

Concerning...Severe potential...Tornado Watch likely 

Valid 271916Z - 272045Z

Probability of Watch Issuance...80 percent

SUMMARY...The threat for tornadoes, some of which may be strong,
very large hail, and damaging winds will increase this afternoon.
Tornado Watch issuance will likely be needed.

DISCUSSION...The airmass across the ArkLaTex region continues to
destabilize this afternoon, with surface temperatures generally
reaching into the 70s and low 80s at 19Z. Rich low-level moisture
already in place across this region combined with steep mid-level
lapse rates of 7-8 C/km are supporting MLCAPE of 1500-2000 J/kg.
Strong deep-layer shear of 50+ kt will easily favor discrete
supercells with initial development. Given a lack of obvious
large-scale forcing for ascent, the primary uncertainty is when
robust storms will form. Best estimate is that with continued
diurnal heating and weak low-level convergence along/south of the
warm front, storms will probably initiate by 20-21Z as a weak
low-level cap continues to gradually erode.

Large to very large (2+ inch) hail will likely be the main threat
with supercells initially, as low-level shear is not very strong at
the moment. But, a low-level south-southwesterly jet should
strengthen later this afternoon into the early evening, and tornado
potential with any discrete storms will increase. A strong tornado
appears possible given 150-200 m2/s2 of effective SRH by mid-evening
if storms can remain generally discrete. An increasing threat for
damaging winds may also eventually unfold later this evening as
upscale growth occurs. Based on towering cumulus becoming evident on
visible satellite imagery across AR, a Tornado Watch will likely
need to be issued.

..Gleason/Thompson.. 03/27/2021

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

ATTN...WFO...JAN...LZK...SHV...FWD...

LAT...LON   31599518 31919552 32739564 34229368 35569201 35709114
            34919116 34089116 33569132 32959197 31649432 31599518

Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Texas, 2021Mesoscale Discussions in Louisiana, 2021Every mesoscale discussion in 2021

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.