SPC AC 071730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Tue May 07 2024

   Valid 081200Z - 091200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
   TEXAS INTO THE MID-SOUTH/MID MISSISSIPPI VALLEY AND LOWER OHIO
   VALLEY...

   ...SUMMARY...
   Scattered to numerous severe thunderstorms appear likely Wednesday
   across parts of the southern Plains into the mid Mississippi, Ohio,
   and Tennessee Valleys. All severe hazards, including tornadoes, very
   large hail, and severe/damaging winds should occur. Some of the
   tornadoes may be strong.

   ...Synopsis...

   An upper low/trough, initially over the northern Plains Wednesday
   morning, will develop east to the Upper Midwest/Great Lakes vicinity
   by Thursday morning. Meanwhile, a more compact upper shortwave
   trough over the Lower Great Lakes will shift east/northeast over the
   Northeastern U.S. This regime will maintain a broad swath of 50-70
   kt southwesterly midlevel/upper flow from the central/southern
   Plains to the Midwest/Mid-South and Northeast. This broad area of
   enhanced flow aloft will contribute to a strongly sheared
   environment atop a very moist boundary-layer. While the upper
   low/trough will progress east through the period, overall height
   falls across the Midwest/OH-TN Valleys are expected to remain modest
   until overnight. Large-scale ascent will be somewhat modest/nebulous
   through the day, with mesoscale features/ascent perhaps more of a
   driver of storm development/evolution.

   At the surface, the general expectation is that a surface low over
   MO early in the period will develop east across the Ohio Valley
   vicinity. A warm front will extend east from the low across
   IL/IN/OH, but there is quite a bit of variability in forecast
   guidance regarding how far north this boundary will retreat during
   the day. A cold front/dryline also is forecast to extend southwest
   from the low across western MO/eastern OK/central TX during the
   afternoon. The cold front will surge east/southeast overnight across
   the Ozarks/Mid-South. These boundaries will collectively focus
   thunderstorm development through the period.

   ...ArkLaTex into the Mid-MS/OH/TN Valleys...

   A very moist and broad warm sector is anticipated, with surface
   dewpoints in the upper 60s to mid 70s F already in place across much
   of the region. Heating into the 80s F and a plume of steep midlevel
   lapse rates overspreading the region will aid in strong
   destabilization (MLCAPE 2500-4000 J/kg). With 40-50 kt effective
   shear magnitudes, organized convection is expected. Convective mode
   may be somewhat messy, with clusters/semi-discrete supercells and
   bowing line segments possible. Little inhibition is expected across
   the warm sector, so thunderstorm coverage could be quite widespread.

   Initial thunderstorms development is likely during the morning near
   the triple point in MO. Most guidance suggests this activity will
   quickly grow upscale into an eastward advancing line/bow across MO.
   More semi-discrete convection is then anticipated by midday/early
   afternoon in the vicinity of the warm front across southern
   IL/western KY, spreading eastward with time across IN/KY/southern OH
   and TN. Additional storms are expected by mid to late afternoon
   along the cold front across AR/southeast OK/northeast TX. Large to
   very large hail (2-3 inch diameter) will be possible with more
   cellular convection given very large instability, steep midlevel
   lapse rates and favorable vertical shear. Tornado potential is also
   apparent, given favorable low-level shear as is evident in enlarged,
   curved 0-3 km forecast hodographs. Mesovortex tornado potential also
   will accompany any bows/QLCS structures as well. Furthermore,
   potentially widespread damaging/severe winds appears possible,
   especially if strong enough cold pools can be generated within
   linear segments. 

   Given little inhibition across the region and somewhat nebulous
   large-scale forcing, convective evolution is somewhat uncertain
   (widespread convection all at once vs. semi-discrete convection
   growing upscale with time, etc). A corridor of higher probability
   severe may develop from southeast MO/southern IL into western KY.
   However, confidence is too low at this time for a categorical
   upgrade.

   ...Iowa and Vicinity...

   Isolated strong to severe thunderstorms appear possible in
   associated with a cold-core upper low across parts of IA and
   vicinity, mainly Wednesday afternoon. Although forecast instability
   and deep-layer shear appear fairly weak/marginal, a few instances of
   hail and strong/gusty winds appear possible. A brief tornado or two
   may also occur along/near the occluded front.

   ...Southern New England into NY and the Mid-Atlantic/Carolinas...

   Occasional hail and strong to locally damaging winds appear possible
   with isolated thunderstorms across parts of NY into southern New
   England as a surface low and attendant cold front move eastward
   through the day. 

   Farther south into the Mid-Atlantic/Carolinas, more substantial
   instability is forecast (up to 2500 J/kg MLCAPE). Large-scale ascent
   is expected to remain weak over the region. However, strong heating
   of a moist boundary-layer and the presence of a surface trough
   extending southward into the Carolinas may be sufficient for greater
   thunderstorm coverage than previously expected. As a result, a
   Slight risk has been extended eastward across parts of VA/NC. Large
   hail and damaging gusts will be possible with thunderstorm activity
   through the evening.

   ..Leitman.. 05/07/2024

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z