SPC AC 141254

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0754 AM CDT Wed Jun 14 2023

   Valid 141300Z - 151200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER
   MISSISSIPPI VALLEY AND SOUTHEAST STATES...

   ...SUMMARY...
   Significant severe thunderstorms capable of producing all severe
   hazards, including very large hail, swaths of intense wind
   gusts/damage, and tornadoes, are possible across much of the Lower
   Mississippi Valley and Southeast states today into tonight.

   ...ArkLaTex/Lower Mississippi Valley/Southeast...
   A significant severe-weather day is expected across a broad region,
   including the possibility of multiple corridors/swaths of intense
   thunderstorms capable of all severe-weather hazards. This scenario
   is largely attributable to seasonally very strong westerlies at
   these latitudes for mid-June, essentially record or near-record
   strength mid/high-level winds based on observed sounding
   climatologies. Mid-level lapse rates are also similarly rare in
   terms of seasonal steepness, as per 00z/12z observed soundings
   across the ArkLatex/Lower Mississippi Valley.

   Regardless of the relatively rare combination of severe-weather
   ingredients at this latitude for mid-June, forecast details still
   remain a bit unclear as far as specifics, although significant
   severe storms are nonetheless probable today into tonight across a
   broad region. This includes very large hail (some greater than 3
   inches in diameter), swaths of intense wind gusts (greater than 70
   kt/80 mph), and tornadoes, a few of which could be strong. The
   greatest potential for tornadoes is currently expected this
   afternoon/evening across the southern half of Alabama into southwest
   Georgia. This is where semi-discrete supercells are plausible
   initially near/south of outflow-related effective boundary, in the
   presence of considerably strengthening low-mid level winds today.

   A series of mid/upper shortwave impulses are expected to shift east
   across the Lower Mississippi Valley and Southeast today amidst
   strong west/southwesterly mid/upper flow. Consistency among various
   forecast guidance shows at least 40-50 kt west/southwest flow
   between 850-700 mb with 60+ kt at 500 mb. A plume of very steep
   lapse rates will overspread the region, and 500 mb temperatures
   around -10 to -11 C will be common. Forecast soundings indicate
   mid-level lapse rates around 8-8.5 C/km atop a moist boundary layer
   with surface dewpoints in the 68-75F range. This will result in
   strong destabilization with MLCAPE values exceeding 3000 J/kg from
   northeast Texas/ArkLaTex to southern Alabama/Georgia and the Florida
   Panhandle.

   Ongoing early day storm clusters across eastern Arkansas appear
   likely to persist southeastward today, and a more isolated cluster
   near the northeast Oklahoma/northwest Arkansas border may continue
   southeastward as well. Large hail will remain a possibility, with
   damaging wind risk potentially increasing later this morning into
   afternoon as these storms interact with a warming/destabilizing
   boundary layer. Additional storms may also develop relatively early
   today across north Texas/ArkLaTex region -- see Mesoscale Discussion
   1033 for more details.

   Overall expectations are for multiple rounds of severe storms
   regionally today into tonight. Locations may see a mix of supercells
   and intense bowing segments during the day, with potential for a
   derecho to develop across the Lower Mississippi Valley.

   ...North Texas...
   Some early day convective development is possible today (more likely
   toward the ArkLaTex), but the categorical Outlook has been shifted
   west-southeastward across the region for another day of potentially
   intense thunderstorm development late this afternoon. If/where
   storms develop, they would be capable of producing large to very
   large hail and severe-caliber wind gusts on a localized basis.

   ...Northeast States...
   Modest air mass destabilization is expected across the region ahead
   of an upper low. One or more north-south orientated bands of
   convection are expected as ascent attendant to this cyclone moves
   through. Instability will be modest, mitigated by weak lapse rates,
   but a few stronger gusts and small hail are possible as these storms
   move east/northeast through the afternoon.

   ..Guyer/Dean.. 06/14/2023

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