SPC AC 252000

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0300 PM CDT Sat Mar 25 2023

   Valid 252000Z - 261200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   WESTERN PENNSYLVANIA/NEW YORK...THE FLORIDA PANHANDLE INTO
   SOUTHERN/CENTRAL GEORGIA...AND SOUTHERN/CENTRAL ALABAMA...

   ...SUMMARY...
   Isolated large hail and damaging winds will remain possible across
   parts of the Florida Panhandle and southern/central Georgia this
   afternoon and early evening. Another round of strong to severe
   storms should occur early Sunday morning across portions of
   southern/central Alabama. Occasional damaging winds remain possible
   for the next hour or two across parts of western Pennsylvania and
   New York.

   ...20Z Update...
   Severe probabilities have been trimmed behind ongoing convection
   that is rapidly progressing across northwest PA into western NY.
   Occasional damaging winds will remain the primary severe threat with
   this activity in the short term given the rather strong
   low/mid-level southwesterly flow present. A cold/stable airmass is
   present downstream of this convection into central PA and
   south-central NY. This will likely limit appreciable severe risk
   with eastward extent into these areas.

   No changes have been made to the Slight Risk areas across the
   Southeast. Widely spaced strong to severe thunderstorms continue in
   and near Severe Thunderstorm Watch 79 across parts of the FL
   Panhandle into southern/central GA. Moderate instability and strong
   deep-layer shear should continue to support updraft organization
   this afternoon, even though large-scale ascent/forcing remains
   nebulous. Isolated hail and damaging winds should remain the primary
   threats.

   Robust convection still appears probable late tonight into early
   Sunday morning from far eastern MS into southern/central AL and
   perhaps far west-central GA, mainly after 26/06Z (1 AM CDT), and
   continuing through the end of the Day 1 period. Large hail and
   strong/gusty winds may occur with any supercell that can develop.

   ..Gleason.. 03/25/2023

   .PREV DISCUSSION... /ISSUED 1123 AM CDT Sat Mar 25 2023/

   ...Synopsis...
   Latest water-vapor imagery shows a compact, well-organized upper low
   over the IL/IN region with a pronounced slot of dry air pushing
   north ahead of the main vorticity maximum. At the surface, a 994 mb
   surface low over southern lower MI is expected to gradually shift
   east/northeast towards the Northeast over the next 12-24 hours in
   tandem with the upper wave. Strong flow and ascent associated with
   this feature is expected to overspread the upper OH river valley and
   lower Great Lakes region, which will support the potential for
   strong to severe thunderstorms through the late afternoon. Across
   the Southeast, ongoing convection along a residual outflow boundary
   is expected to persist into the mid/late afternoon and intensify to
   severe limits. A late-night round of strong to severe thunderstorms
   is expected during the early morning hours Sundays across parts of
   MS/AL as the outflow boundary advances north as an effective warm
   front tonight. 

   ...Upper Ohio River Valley...
   Considerable clearing is ongoing across parts of southern OH into
   far southwest PA as the aforementioned dry slot advances northward.
   This clearing has allowed temperatures to warm into the low to mid
   60s ahead of an approaching cold front, which, as of 15:45 UTC, is
   slightly warmer than most 12 UTC guidance. Consequently, low-level
   lapse rates have already increased to around 7 C/km where warming
   has been maximized. The combination of warming surface temperatures,
   mid to upper 50s dewpoints, and cool temperatures aloft will support
   increasing buoyancy through the mid-afternoon hours. Shallow
   convection evident in visible imagery along the front across western
   OH is expected to intensify as it moves into the destabilizing air
   mass. Strong kinematic fields sampled by morning soundings and
   recent VWP observations will be favorable for organized convection,
   and the steep low-level lapse rates will allow for efficient mixing
   of 50+ knot boundary layer winds to the surface. As a result,
   damaging winds appear likely across eastern OH to western PA and
   portions of western NY, though a few instances of severe hail and
   perhaps a brief tornado are plausible. 

   ...Southeast Georgia and northern Florida...
   GOES IR imagery has shown a slow intensification of ongoing
   convection across portions of central/southern GA. Although this
   region will become increasingly displaced from synoptic ascent and
   stronger mid-level flow through the day, regional VWPs show
   sufficient deep-layer shear for organized convection through peak
   daytime heating. Furthermore, quality low-level moisture (sampled by
   the 12 UTC TLH and JAX soundings) will migrate northeastward ahead
   of the convection, allowing for MLCAPE values to increase to near
   2000 J/kg. As a result, the recent intensification trend will likely
   continue through the day and regionally augment the potential for
   damaging winds and hail. 

   ...Alabama...
   The residual outflow boundary draped across the Southeast from prior
   convection over the past 24 hours is expected to gradually lift to
   the north through the day, eventually becoming draped from southeast
   LA into southern MS and central AL by late tonight. A weak mid-level
   perturbation is expected to move into the southern Plains/lower MS
   River Valley during the 00-12 UTC period, which will help strengthen
   southerly 850 mb flow and bolster isentropic ascent over the
   boundary. Despite some nocturnal cooling, profiles are expected to
   be weakly capped with MLCAPE values near 1000-2000 J/kg during the
   overnight period. Elongated hodographs featuring around 50 knots of
   effective shear should support organized cells, including splitting
   supercells, that will pose a severe wind/hail risk (though storm
   motions along the boundary may limit individual cell longevity and
   promote upscale growth into clusters). Timing of this convection
   remains uncertain with recent CAMs showing spread in the onset of
   convective initiation, but the probability of CI prior to 12 UTC has
   increased sufficiently to introduce higher risk probabilities.

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