SPC AC 270555

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1255 AM CDT Wed May 27 2020

   Valid 271200Z - 281200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER MUCH OF
   CENTRAL TEXAS...

   ...SUMMARY...
   Severe thunderstorms producing very large hail and significant wind
   gusts are expected over parts of central Texas late this afternoon
   and evening, with lesser severe-weather potential over parts of the
   central Gulf Coast region and Carolinas.

   ...Synopsis...
   An upper low will remain nearly stationary over southeast OK, with
   various waves rotating around from TX to the lower MS Valley. A
   leading wave will move northeast across MS and AL during the
   afternoon, providing a lobe of coolness aloft and increased
   deep-layer mean winds favoring scattered strong storms across LA, MS
   and AL. 

   To the west, a secondary wave will drop south across northwest TX
   during the late afternoon, and into central TX during the evening.
   Here, access to steep low-level lapse rates under a strong northwest
   flow regime is likely to result in damaging storms.

   Elsewhere, while upper ridging will occur over the Northeast,
   warm/moist advection across parts of ME may support isolated,
   marginal hail.

   ...Texas...
   Low pressure will gradually deepen over western and central TX as a
   cold front surges south across the Panhandle and South Plains. Much
   of the day will be free of storms across central TX, allowing
   maximum heating. Storms are expected to initiate around 21Z over
   west-central TX, with a rapid expansion east/southeast through
   evening. Steep lapse rates aloft will favor vigorous updrafts, with
   storms initially supercells exhibiting substantial forward
   tilt/tight reflectivity gradients. Forecast hodographs indicate a
   common significant hail setup for the southern Plains, with weak
   southerly surface winds/marginal SRH beneath strong mid and upper
   level winds creating lengthy hodographs. In addition to very large
   hail, localized wind gusts around 75 mph will be possible as cold
   pools build.

   ...Central Gulf Coast states...
   Steepening deep-layer lapse rates will lead to substantial
   instability with MUCAPE over 2000 J/kg over much of LA, MS, and
   southern AL this afternoon. All this will occur beneath modest, mean
   southerly flow aloft, resulting in scattered, mixed-mode storms.
   Localized wind damage or marginally severe hail is possible.
   Less-than-ideal shear, including weak winds below 850 mb, precludes
   a more substantial supercell threat.

   ...Carolinas...
   A weak tropical disturbance is forecast to shift north across the
   Carolinas today resulting in moistening and destabilization well
   inland. Little if any heating will occur, but instability will
   become sufficient for a few strong storms focused near the surface
   trough developing over the central Carolinas. As a 30-40 kt midlevel
   speed max moves north over the area, effective SRH of 200-300 m2/s2
   may develop, favoring storm-scale rotation and a possible tornado or
   wind gust threat.

   ...Northern Maine...
   Strong heating will occur today, with 60s dewpoints contributing to
   over 1500 J/kg MLCAPE near a diffuse warm front across northern
   Maine. Isolated storms are possible where low-level convergence is
   sufficient near the wind shift. Forecast soundings indicate an
   uncapped air mass, with light but veering winds with height
   resulting in small, but favorably shaped hodographs for single cell
   storms. Given cool temperatures aloft, marginally severe hail is
   possible.

   ..Jewell/Lyons.. 05/27/2020

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