SPC AC 291730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Tue Mar 29 2022

   Valid 301200Z - 311200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   LOUISIANA...EASTERN ARKANSAS...MISSISSIPPI...WESTERN
   TENNESSEE...ALABAMA...AND THE WESTERN FLORIDA PANHANDLE...

   ...SUMMARY...
   A regional outbreak of severe thunderstorms is expected on Wednesday
   across the Lower Mississippi Valley and Southeast. All severe
   hazards are possible, including widespread damaging winds, some over
   75 mph, and several tornadoes, some of which could be strong (EF2+).

   ...Synopsis...
   A shortwave trough will eject from the southern Plains across the
   lower/mid MS Valley on Wednesday while acquiring a negative tilt. An
   80-100+ kt south-southwesterly mid-level jet will accompany the
   shortwave trough passage. Low-level southerly flow is also expected
   to be very strong, with 50-70+ kt winds forecast at 850 mb. The
   primary surface low should be located over IA at the start of the
   period, with a cold front extending southward from this low across
   the central/southern Plains. A secondary surface low in closer
   proximity to the shortwave trough is forecast to develop from
   eastern OK to the Mid-South vicinity by Wednesday evening.

   At least low to mid 60s surface dewpoints are expected to return
   northward across the lower MS Valley and Southeast ahead of the
   secondary surface low, with the surface warm sector becoming
   increasingly pinched off with northward extent into the mid MS and
   OH Valleys. With strong forcing for ascent associated with the
   shortwave trough overspreading the warm sector through the day,
   thunderstorms will develop and move east-northeastward ahead of the
   cold front while posing a threat for both widespread damaging winds
   and several tornadoes.

   ...Lower Mississippi Valley into the Southeast...
   A line of convection aided by strong low-level warm advection will
   likely be ongoing at the start of the period from the Ozarks
   southward across AR to east TX. This activity should continue to
   pose a threat for at least isolated damaging winds and tornadoes as
   it moves eastward Wednesday morning. Fairly widespread cloud cover
   ahead of the line and modest mid-level lapse rates should temper the
   degree of destabilization to some extent. Still, the increasing
   low-level moisture in tandem with filtered diurnal heating are
   expected to aid in sufficient boundary-layer destabilization to
   support surface-based storms. MLCAPE around 500-1000 J/kg should
   develop ahead of the line across LA into MS and surrounding areas by
   early Wednesday afternoon.

   This QLCS should strengthen Wednesday afternoon as it moves across
   northeastern LA, eastern AR, southeastern MO, and into much of the
   lower MS Valley and Mid-South. Aided by strengthening low/mid-level
   flow, increasing low-level and deep-layer shear will both become
   very strong, supporting updraft organization. With a primarily
   linear storm mode expected, widespread severe/damaging winds appear
   likely. The presence of a 50-70+ kt south-southwesterly low-level
   jet, and even stronger flow up to 75 kt at 700 mb, should enhance
   the prospects for significant severe wind gusts of 75+ mph at the
   surface within the most intense portions of the line Wednesday
   afternoon and evening. Very favorable low-level shear and
   elongated/sickle-shaped hodographs in the boundary layer will likely
   also support low-level rotation with embedded mesovorticies within
   the QLCS. Several tornadoes should occur across the lower MS Valley
   and Southeast in this regime, with circulations moving quickly
   east-northeastward.

   The potential for supercells to develop ahead of the line, or
   perhaps embedded within the line with southward extent, remains
   unclear. Any cells that can form ahead of the line would be favored
   to produce tornadoes, but the quick eastward progression of the QCLS
   may limit this possibility. Still, some guidance suggests the
   southern part of the line may become more broken with time Wednesday
   afternoon/evening. If this occurs, then a threat for embedded
   supercells capable of producing multiple strong (EF2+) tornadoes
   would exist. At this point, the greatest tornado potential may focus
   along southern portions of the line in MS/AL where a semi-discrete
   mode seems more plausible. Regardless, a continued threat for both
   damaging winds and tornadoes will likely persist Wednesday evening
   and overnight as convection spreads from the lower MS Valley into
   the TN Valley and Deep South. Thunderstorms should eventually weaken
   with eastward extent early Thursday morning as they outpace the
   low-level moisture return and encounter a less favorable
   thermodynamic environment.

   ...Mid Mississippi Valley into the Ohio Valley...
   Less low-level moisture and weaker instability are forecast across
   the mid MS Valley and OH Valley compared to locations farther south.
   However, enough boundary-layer instability should be present for the
   line of storms to produce scattered to perhaps numerous damaging
   winds as it moves eastward given the strength of the low-level flow.
   A few tornadoes may also occur with favorable low-level shear also
   present. The lack of stronger instability precludes greater severe
   probabilities across this region at this time.

   ..Gleason.. 03/29/2022

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