SPC AC 140550

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1250 AM CDT Tue Apr 14 2026

   Valid 141200Z - 151200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE MIDWEST...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
   TO SOUTHERN PLAINS AND PARTS OF THE NORTHEAST...

   ...SUMMARY...
   Severe thunderstorms are expected this afternoon through tonight
   from the southern Plains to the Great Lakes. Large to very large
   hail, a few tornadoes (some strong), and damaging wind gusts will be
   possible, particularly across parts of eastern Iowa, northern
   Illinois, and southern Wisconsin. Additional severe storms, mainly
   producing strong wind gusts, will be possible across parts of the
   Northeast this afternoon.

   ...Synopsis...
   An upper wave is evident in recent water-vapor imagery across the
   southern Great Basin. This trough will translate east into the
   Plains through today, reaching the Great Lakes region by tonight.
   This will support slight deepening of a diffuse surface low analyzed
   over the central High Plains as it drifts east towards the lower MO
   River Valley. Ahead of the low, an expansive warm sector
   (characterized by widespread mid to upper 60s dewpoints) remains in
   place from the southern Plains northeastward into the upper MS
   Valley region. Strong to severe thunderstorms are expected along a
   composite outflow boundary/warm front from eastern IA into southern
   WI/northern IL as well as along a dryline draped from eastern KS
   into OK and TX. Further east, a mid-level wave associated with
   ongoing convection over the Great Lakes will support
   re-intensification/re-development of strong/severe storms across the
   Northeast. 

   ...Midwest...
   An outflow boundary emanating from the ongoing MCS across the Great
   Lakes will likely be draped across the Midwest early this morning.
   This boundary is forecast to drift northward within a southerly flow
   regime as an effective warm front ahead of the approaching surface
   low and upper wave. Latest guidance generally depicts this boundary
   stalling across eastern IA into southern WI by late afternoon when
   daytime heating and ascent ahead of the upper wave will erode
   inhibition and promote convective initiation along the boundary. 

   Dewpoints in the mid to upper 60s coupled with steep mid-level lapse
   rates (already noted in upstream 00z RAOBs) will support MLCAPE
   values near 2500 J/kg by late afternoon. Moderate buoyancy combined
   with 45-55 knots of effective bulk shear will be highly favorable
   for organized convection. Capping at the base of the EML should
   initially limit thunderstorm coverage and favor discrete supercells
   along the boundary. In addition to very large hail (possibly up to
   2-3 inches in diameter), enhanced low-level SRH along the boundary
   may support a corridor of locally higher tornado potential,
   including the potential for significant tornadoes. With time,
   easterly storm motions along the boundary will promote upscale
   growth with an increasing wind threat heading into the late evening
   hours. 

   The primary uncertainty will be the location of the boundary by late
   afternoon. 30% hail and 10% tornado probabilities were adjusted to
   reflect the most likely placement of the boundary based on a
   consensus of guidance; however, exact placement of the boundary will
   be conditional on the precise evolution of the morning MCS.
   Similarly, how quickly upscale growth occurs after initiation may
   modulate the duration of the significant hail/tornado threat.

   ...Kansas into Oklahoma and Texas...
   Modest height falls across the central to southern Plains combined
   with weak convergence along the dryline will likely support isolated
   to perhaps scattered thunderstorms from eastern KS southward into TX
   this afternoon. Consensus among latest HREF/REFS guidance is that
   initiation is most probable across northwest TX into central OK -
   possibly ahead of a subtle mid-level wave, though in reality the
   unfocused nature of the broad-scale ascent suggests that initiation
   will be possible anywhere along the dryline where low-level
   convergence can be maximized. Regardless, ample buoyancy within the
   warm sector (2500-3000 J/kg MLCAPE sampled in evening RAOBs) coupled
   with 30-40 knots of effective bulk shear will support supercells
   with an attendant threat for large hail (possibly exceeding 2 inches
   in diameter). Some tornado threat will likely materialize around and
   after 00 UTC as the nocturnal jet strengthens and enlarges low-level
   hodographs. 

   ...Northeast...
   A low-amplitude upper wave associated with an ongoing MCS across the
   Great Lakes will migrate eastward towards the Northeast through the
   day. Residual convection associated with the MCS may linger through
   morning before re-intensifying by early afternoon as daytime heating
   supports steepening low-level lapse rates and increasing MLCAPE
   values (likely up to the 500-1000 J/kg range). While buoyancy will
   likely remain weak, 35-40 knot bulk shear through the CAPE-bearing
   layer and focused ascent ahead of a low-amplitude upper wave will
   likely support organization of convective bands with an attendant
   threat for strong to severe winds.

   ..Moore/Wendt.. 04/14/2026

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