SPC AC 161954

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0254 PM CDT Tue Apr 16 2024

   Valid 162000Z - 171200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
   MIDWEST AND MIDDLE MISSISSIPPI VALLEY...

   ...SUMMARY...
   Scattered severe thunderstorms are likely today, especially across
   northern Missouri, Iowa, and northwestern Illinois. Large hail,
   damaging winds, and tornadoes are expected. More isolated activity
   could develop as far south as the Ozarks and Mid-South.

   ...Synopsis...
   The previous forecast largely remains on track with only minor
   modifications made to reflect convective trends across portions of
   NE, KS, and western MO. Recent analyses show that the best kinematic
   environment resides from central AR into MO and southern/southeast
   IA. However, thermodynamic limitations (largely due to warm
   temperatures in the 850-700 mb as sampled by the 18 UTC DVN and 19
   UTC ILX soundings and modest mid-level lapse rates) and unfavorable
   storm interactions have modulated convective intensity/organization
   thus far. Further intensification remains possible through the
   afternoon/early evening amid peak diurnal heating (see MCD 460 for
   additional near-term details). Across far eastern NE into western
   IA, cold temperatures aloft (supporting surface-based lifted indices
   between -7 to -9 C) combined with plentiful ambient low-level
   vorticity along surface boundaries continues to support a tornado
   threat. See MCD 461 for additional details.

   ..Moore.. 04/16/2024

   .PREV DISCUSSION... /ISSUED 1140 AM CDT Tue Apr 16 2024/

   ...Midwest/Middle Mississippi Valley...
   Regenerative scattered showers and thunderstorms continue to occur
   across western/northern Missouri into much of Iowa at late morning,
   originating with a warm sector that narrows with north-northwestward
   extent into southern Iowa and far east/northeast Nebraska in
   vicinity of the surface low. Even while warm-sector cloud breaks
   have been limited, steady early-spring heating and low-level
   moistening is occurring with surface dewpoints rising through the
   lower 60s F.

   This development coincides with an intense/cyclonically curved 90+
   kt polar jet and a low-level jet that will remain diurnally strong
   (40+ kt). Modest cloud breaks aside, destabilization will be further
   aided by a pocket of steep mid-level lapse rates and cold
   temperatures aloft on the southeast side of the upper trough/low.
   Scenario supports a risk for supercells especially across northern
   Missouri into southern/eastern Iowa and northwest Illinois.

   Steep mid-level lapse rates will aid in hail production, with a few
   golf ball or 2+ inch diameter stones possible with the more robust
   cores. Tornadoes will also be a concern, as the enhanced
   boundary-layer flow and enlarged/curved hodographs associated with
   the low-level jet will aid in updraft rotation. The main tornado
   potential is still expected to be focused along/near the warm front
   in southern/eastern Iowa where the stronger low-level shear is
   forecast. A strong (EF2+) tornado is possible. Isolated to scattered
   damaging winds are otherwise expected regionally.

   Farther south toward the Ozarks and Mid-South, a potential for at
   least isolated severe thunderstorms remains apparent into this
   evening, with a moist/confluent regime near/ahead of the
   eastward-advancing front. Mid-level lapse rates will remain limited.
   However, steady low-level moistening will tend to counteract a
   tendency for nocturnal boundary cooling, netting a scenario with
   limited warm-sector inhibition tonight, supporting the possibility
   of supercells capable of all severe hazards including a tornado
   risk, even if severe storms remain relatively isolated overall.

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