SPC AC 141630

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CDT Fri Mar 14 2025

   Valid 141630Z - 151200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE MID MISSISSIPPI VALLEY INTO THE LOWER OHIO VALLEY AND
   MID-SOUTH...

   ...SUMMARY...
   A regional outbreak of severe thunderstorms is likely this afternoon
   through tonight across parts of the Lower/Mid Mississippi Valley and
   portions of the Lower Ohio Valley and Mid-South. Numerous tornadoes,
   several of which could be strong, widespread severe gusts ranging
   from 60 to 100 mph, and scattered large hail up to baseball size all
   appear likely.

   ...Synopsis...
   Water-vapor imagery late this morning indicates a powerful and
   negatively tilted mid/upper-level shortwave trough over the southern
   High Plains. An intense mid-level jet (with winds of 100-115+ kt at
   500 mb) will continue to round the base of the trough, and quickly
   eject northeastward across OK and eastern KS this afternoon. This
   mid-level jet will move over parts of the mid MS Valley and Midwest
   this evening and tonight in tandem with the northeastward-advancing
   shortwave trough. Strong ascent aloft associated with both of these
   features will overspread portions of the central CONUS as a deep
   surface cyclone develops northeastward from the central High Plains
   into the Upper Midwest this afternoon through tonight. In the low
   levels, a dryline will surge eastward across the southern/central
   Plains through the day, eventually arcing from the low southeastward
   into the Ozarks. A large area of significant severe potential
   remains evident across parts of the lower/mid MS Valley into the
   Midwest and Mid-South.

   ...Mid Mississippi Valley into the Midwest and Mid-South...
   Ample diurnal heating is expected through this afternoon ahead of
   the cyclone, with elevated convection already occurring across parts
   of eastern OK into southeast KS and southwest MO. More robust,
   surface-based thunderstorms will likely develop by early/mid
   afternoon (18-21z) along/east of the dryline from parts of eastern
   NE southward into eastern KS/western MO, as a southerly low-level
   jet attempts to bring shallow boundary-layer moisture northward into
   the mid MS Valley and vicinity. The northern portion of this
   convection will be oriented more orthogonal to the ejecting
   mid-level jet, and current expectations are for quick upscale growth
   into a fast northeastward-moving band, posing a risk for widespread
   severe/damaging winds as this activity moves into IA and towards the
   MO/IA/IL border region. Given the strength of the low/mid-level flow
   and presence of steep lapse rates aloft, along with a well-mixed
   boundary layer, intense thunderstorm straight-line gusts peaking
   locally in the 80-100 mph range are possible with the stronger
   cores/inflections in the band as it matures and moves across parts
   of the mid MS Valley, and eventually into the southwestern Great
   Lakes this evening through tonight. 

   Additional, potentially more discrete, severe thunderstorms will
   develop this afternoon farther southeast along the wind shift into
   central/eastern MO, generally on the northern periphery of somewhat
   better low-level moisture from southeast MO southward into the
   Mid-South. Stronger high-level flow and ample deep-layer shear over
   these will likely promote at least semi-discrete supercells. Latest
   model guidance, including various convection-allowing HREF members,
   suggest scattered supercells developing late this afternoon and
   evening as far south as the MS/AR/TN border region. Have nudged
   severe probabilities and the corresponding SLGT/ENH/MDT westward a
   little in western/central MO to account for a slightly earlier
   initiation. Various NAM/RAP forecast soundings strongly favor
   intense supercells capable of large to very large hail (up to 2-3
   inches in diameter), and potentially multiple strong to intense
   tornadoes this evening as effective SRH rapidly increases in tandem
   with a southerly low-level jet strengthening to 50-65+ kt. This
   substantial severe threat is expected to continue eastward overnight
   into parts of the lower OH Valley/Midwest, before convection
   eventually outpaces the low-level moisture return and weakens.

   ...Lower Mississippi Valley...
   Large-scale forcing for ascent appears a bit more nebulous/weak
   farther south into the lower MS Valley. Still, the 12Z suite of
   guidance shows some potential for surface-based thunderstorms
   developing by late this afternoon across the ArkLaMiss region. While
   the stronger low/mid-level flow and forcing are expected to remain
   to the north of this region, greater low-level moisture and related
   instability will be present. This favorable thermodynamic and
   kinematic environment will support supercells, with associated
   threat for large to very large hail, damaging winds, and tornadoes.
   Some of tornadoes could be strong this evening with any sustained
   supercells, especially across central MS and vicinity. Have expanded
   the ENH to account for this potential, and consideration was given
   to expanding the MDT southward into central MS as well. But, there
   is still some uncertainty with overall thunderstorm coverage.

   ..Gleason/Squitieri.. 03/14/2025

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