SPC AC 281941

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0241 PM CDT Fri Jun 28 2024

   Valid 282000Z - 291200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
   PLAINS TO THE MIDDLE MISSISSIPPI VALLEY...

   ...SUMMARY...
   Large hail, damaging winds, and a couple of tornadoes may occur from
   parts of the central Plains into the mid/upper Mississippi Valley
   through tonight.

   ...20z Update...

   Only minor adjustments have been made to the 10 percent general
   thunderstorm line for the 20z update. Severe probabilities remain
   unchanged from the prior outlook. Isolated strong to severe storms
   still appear possible from the central High Plains into parts of
   IA/MO from late afternoon into tonight. For more details, refer to
   previous outlook discussion below, and any forthcoming mesoscale
   convective discussions.

   ..Leitman.. 06/28/2024

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Fri Jun 28 2024/

   ...Synopsis...
   An upper low over the northern Rockies/High Plains will progress
   eastward today to the Upper Midwest. At the surface, an occluded low
   is forecast to meander slowly eastward over northern MN through this
   evening, while a secondary low consolidates over central KS. An
   occluded/cold front extending from the northern MN low will develop
   slowly southeastward across the central Plains and mid MO Valley
   this afternoon. This boundary will likely serve as a focus for
   strong/severe convection later today.

   ...Central Plains into the Mid Mississippi Valley...
   Better forcing for ascent associated with the upper trough/low
   should generally remain displaced to the north of the central Plains
   and mid MO Valley through much of the day. Also, the lingering
   effect of morning clouds/precipitation will be to slow diurnal
   destabilization to some extent. Still, low-level convergence along
   the cold front and glancing large-scale ascent will probably be
   sufficient for convective initiation through 20-00Z across parts of
   IA into eastern NE, and northeast KS into northern MO. Even modest
   daytime heating of the moist low-level airmass ahead of the front
   will support a narrow corridor of moderate to locally strong
   instability. Strengthening westerly winds through mid/upper levels
   will foster strong deep-layer shear and updraft organization.

   Initial development along the cold front from eastern NE into
   central IA may be supercellular, with an associated threat for large
   hail. Upscale growth into clusters and short line segments with a
   greater severe/damaging wind threat seems probable with time this
   evening. The eastern extent of the severe risk across the mid MS
   Valley will be modulated by the narrow zone of stronger instability,
   and convection should gradually weaken as it continues eastward late
   this evening and overnight. The tornado threat across these areas
   today appears less clear. While a modest southwesterly low-level jet
   will aid in sufficient low-level shear for updraft rotation, it
   remains unclear whether multiple supercells will be able to persist
   into the early evening hours. Still, some threat for a couple
   tornadoes remains apparent, mainly near/northeast of the surface low
   in northeast KS and vicinity where low-level shear should be locally
   maximized.

   A separate area of high-based convective development should occur
   this afternoon across the central High Plains, along/north of the
   cold front in a weak low-level upslope flow regime. This activity
   will move generally east-southeastward through the evening through a
   very well-mixed boundary layer, with generally weak to moderate
   instability present. Although low-level winds should remain modest,
   gradually increasing westerly flow at mid/upper levels should
   support sufficient deep-layer shear for convective organization.
   Severe/damaging winds appear to be the main threat as one or more
   small clusters continue east-southeastward across western/central
   NE/KS late this afternoon and evening. Isolated gusts of 75+ mph may
   occur if convection can become well organized into a small bowing
   cluster. Some large hail also appears possible, particularly with
   any initial supercells.

   ...Northern Plains into the Upper Mississippi Valley...
   Isolated to scattered thunderstorms should develop along an occluded
   front extending into parts of ND as the upper trough/low moves
   eastward over the northern Plains today. While instability appears
   fairly modest, occasional hail and strong/gusty winds may occur with
   the more robust convection given the presence of sufficient
   deep-layer shear.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z