SPC AC 150559

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1259 AM CDT Wed May 15 2024

   Valid 151200Z - 161200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE SOUTHERN PLAINS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL
   FLORIDA AND PARTS OF THE CAROLINA PIEDMONT...

   ...SUMMARY...
   Several severe thunderstorms should move across the southern Plains
   this afternoon and evening, accompanied by severe gusts (some
   possibly exceeding 75 mph), large hail, and perhaps a couple of
   tornadoes. Scattered severe thunderstorms are also possible this
   morning into the afternoon over parts of the northern and central
   Florida Peninsula, as well as the Carolinas.

   ...Synopsis...
   A mid-level trough will progress across the Southeast as a second
   mid-level trough impinges on the southern Plains today. Along the
   East Coast, a weak surface low will impinge on the Atlantic
   Coastline as a surface baroclinic boundary drapes across the central
   FL Peninsula. Moisture advection ahead of the surface low over the
   Carolinas, and south of the baroclinic boundary over the central FL
   Peninsula, will encourage strong to potentially severe thunderstorm
   development given the presence of adequate vertical wind shear.
   Meanwhile, strong moisture advection ahead of a rapidly developing
   surface cyclone over the southern High Plains will promote the
   development of several severe thunderstorms by afternoon peak
   heating over the southern Plains.

   ...Central FL Peninsula...
   Thunderstorms should be initiating and strengthening along a
   baroclinic boundary across northern into central portions of the FL
   Peninsula by the start of the period (12Z) today. During the
   morning, a 50+ kt westerly 500 mb jet streak will overspread the
   baroclinic boundary, where 30+ kts of southwesterly 850 mb flow will
   also be in place, contributing to curved, elongated hodographs.
   30-40 kts of effective bulk shear, combined with 2000-3500 J/kg
   SBCAPE (driven by 7+ C/km mid-level lapse rates overspreading mid
   70s F dewpoints) could result in semi-discrete supercell structures.
   However, a predominantly linear convective mode could be favored, as
   the mean wind field will largely parallel the surface baroclinic
   boundary. Severe wind and hail should be the main threats, though a
   couple of tornadoes could also occur, especially if any supercell
   structures can maintain themselves ahead of the convective line.

   ...Carolinas...
   Ahead of the weak surface low, adequate boundary layer heating and
   moistening should occur beneath 6.5-7 C/km low and mid-level lapse
   rates, supporting a marginally unstable but uncapped airmass by
   afternoon. The combination of surface heating and some dynamic
   lifting induced by the approaching mid-level trough, will support
   late morning/early afternoon thunderstorm initiation. Stronger
   westerly flow aloft from the mid-level trough will overspread the
   warm sector, contributing to 30-40 kts of effective bulk shear.
   Also, with the onset of diurnal heating, surface temperatures
   warming into the low 80s F amid mid 60s F dewpoints will boost
   SBCAPE to at least 1500 J/kg. Given relatively elongated, straight
   hodographs, splitting supercells and merging multicells should occur
   through the afternoon, accompanied by a severe wind and hail risk.

   ...Southern Plains...
   Surface lee troughing along the southern High Plains should become
   generally more pronounced with increasing deep-layer ascent, driven
   by an approaching mid-level trough. Through the afternoon, strong
   diurnal heating will contribute to the development of a deep,
   well-mixed, uncapped boundary layer. 8-9 C/km lapse rates will
   reside in the boundary layer and into the mid-levels, resulting in
   inverted-V profiles across the TX panhandle with 1500-3000 J/kg of
   tall, thin CAPE. Initial storms should be high-based, with
   supercells and multicells possible given modestly curved, elongated
   hodographs. Large hail and severe gusts will be the initial
   concerns. However, ample evaporative cooling within the deep,
   well-mixed boundary layer will encourage the development of deep,
   strong cold pools with a tendency to merge. Severe-wind-producing
   clusters are expected to rapidly propagate from the TX/OK Panhandles
   into northwestern OK and eventually southern KS by late
   afternoon/early evening, preceded by richer low-level moisture and a
   strengthening low-level jet. These conditions may augment severe
   wind production (including the potential for 65+ kt gusts) with the
   stronger storm clusters. Supercell structures may also initiate in
   the warm-air advection regime along the KS/OK border during the
   evening, with all severe hazards possible, before storms are
   overtaken by merging cold pools from the west. Storms should
   gradually weaken overnight as they either become undercut by overly
   aggressive cold pools, or they outpace the buoyancy axis by the time
   they reach far eastern KS/northeastern OK. 

   More isolated thunderstorms may initiate along a diffuse dryline
   across western TX toward the Rio Grande. Given overall weak forcing,
   confidence in thunderstorm development and sustenance is not overly
   high. Nonetheless, over 1500 J/kg SBCAPE amid elongated hodographs
   suggests that any storm that can form and mature may become
   supercellular, accompanied by severe wind and hail.

   ..Squitieri.. 05/15/2024

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