SPC MD 199

MD 0199 CONCERNING SEVERE POTENTIAL…TORNADO WATCH LIKELY FOR EASTERN LOUISIANA AND MUCH OF MISSISSIPPI

Mesoscale Discussion 0199
NWS Storm Prediction Center Norman OK
1007 AM CDT Sat Mar 15 2025

Areas affected...Eastern Louisiana and much of Mississippi

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

Valid 151507Z - 151700Z

Probability of Watch Issuance...95 percent

SUMMARY...A Particularly Dangerous Situation Tornado Watch will be
issued soon. A tornado outbreak with multiple intense to violent
long-track tornadoes is likely.

DISCUSSION...Morning observational data continues to support a
likely tornado outbreak today across parts of eastern Louisiana and
Mississippi. 12Z RAOBS from LCH and LIX indicate rich low-level
moisture featuring a mean mixing ratio of 14 to 15 beneath a steep
EML with mid-level lapse rates of 8 to nearly 9 C/km. This
thermodynamic profile, combined with broken cloud cover across
Louisiana and southern Mississippi suggest substantial heating will
occur and strong instability will be present for much of the day
today. The EML will play a critical role in the storm mode today.
Discrete supercells are anticipated given the EML which will
suppress more widespread convection and also provide enough
mid-level dry air for potentially multiple well-organized supercells
in close proximity through the day. In addition, 12Z RAOB data along
the Gulf Coast is consistent with the data observed the morning of
historical tornado outbreaks across Mississippi and Alabama.

Strong shear is already present across Louisiana and Mississippi
this morning with effective shear 40 to 60 knots at the LIX/LCH/JAN
12Z RAOBs. However, shear will increase further through the morning
as mid-level flow strengthens with the mid-level jet streak
overspreading more of the warm sector and with secondary surface
cyclogenesis in the mid-Mississippi Valley. Early evidence of this
secondary low-pressure center has already been observed with a
sub-995mb surface low analyzed northwest of Little Rock, Arkansas at
15Z. This surface low will continue to deepen and consolidate
through the day which will keep flow backed across the warm sector
and result in further strengthening of the already strong low-level
jet. By mid-afternoon, a low-level jet of 65 to 70 knots is forecast
with corresponding 0-1km SRH of 300 to 500 m2/s2. The presence of
nearly pure streamwise vorticity in the lowest 1km will create an
environment extremely conducive to the stretching of the ambient
low-level vorticity.

Confluence bands across Louisiana this morning likely represent the
initial supercell initiation zone for the storms of greatest concern
this afternoon. Multiple bands of supercells are possible. Once
mature supercells develop in the environment south of the messier
convection, there should be very little to interrupt their longevity
through the afternoon.

Given the aforementioned factors, many discrete supercells are
expected in an environment which is extremely conducive to tornadic
activity. Therefore, a tornado outbreak appears imminent with the
potential for multiple, intense to violent long track tornadoes from
mid-day through this evening across eastern Louisiana and much of
Mississippi. A Particularly Dangerous Situation Tornado Watch will
be issued soon to address this threat.

..Bentley/Gleason.. 03/15/2025

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

ATTN...WFO...BMX...HUN...MOB...MEG...JAN...LIX...LCH...SHV...

LAT...LON   33289093 33959023 34478950 34728889 34648832 34558813
            33698827 31718846 31238894 30768995 30779104 31009190
            31559220 32039197 32649162 33289093 

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