SPC AC 171708

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1208 PM CDT Tue Sep 17 2024

   Valid 181200Z - 191200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE GREAT PLAINS...

   ...SUMMARY...
   Isolated severe wind and hail are possible across a portion of the
   Great Plains during the late afternoon and evening on Wednesday.

   ...Great Plains...

   A stacked cyclone will slowly shift east/northeast from eastern MT
   to southern SK/MB on Wednesday into early Thursday. At the surface,
   a dryline will be oriented from the eastern Dakotas into
   western/central NE, then southward across western KS and into the
   OK/TX Panhandle vicinity. With time, a cold front will merge with
   this feature on the northern end across the Dakotas during the
   nighttime hours. Deep-layer south/southwesterly flow will remain
   somewhat enhanced across the northern/central Plains toward the
   Upper Midwest as the mid/upper trough shifts east. Around 30-35 kt
   effective shear magnitudes are forecast along the extent of the
   dryline. Meanwhile, surface dewpoints in the 60s will be maintained
   ahead of the surface boundary in a persistent southerly low-level
   warm advection regime. Midlevel temperatures are forecast to be
   somewhat warm, precluding steeper lapse rates. Nevertheless,
   1000-2000 J/kg MLCAPE is expected, with the greatest instability
   expected near/north of the Mid-MO Valley. 

   Weakening convection may be ongoing Wednesday morning in the
   vicinity of the Mid-MO valley, with areas of cloud cover extending
   northward into MN. Where stronger heating occurs, low-level
   convergence along the surface dryline and any remnant outflow
   boundaries may focus thunderstorm development during the afternoon.
   Large-scale ascent will be nebulous, with stronger forcing focused
   near/north of the international border. Instability and shear will
   decrease with southward extent into KS and the southern Plains. This
   will limit coverage and intensity of convection to some degree.
   Nevertheless, isolated strong to severe storms may pose a risk for
   locally damaging gusts and hail.

   Additional thunderstorms may develop overnight as the surface cold
   front overtakes the dryline from the far eastern Dakotas into MN.
   This activity will be driven by warm advection and likely be
   elevated. Severe potential currently appears low beyond the 03-06z
   time frame.

   ..Leitman.. 09/17/2024

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