SPC AC 261305

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0805 AM CDT Tue Jun 26 2018

   Valid 261300Z - 271200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   KANSAS AND MISSOURI...

   ...SUMMARY...
   Severe thunderstorms are likely across the Lower Missouri Valley and
   the south-central Plains today and tonight, with other severe storms
   expected across other parts of the Midwest, Dakotas, and the
   Tennessee Valley into the Southeast States.

   ...Central/eastern Kansas into Missouri and northern portions of
   OK/AR...
   A mid/upper-level low centered over Iowa early today will continue
   generally east-northeastward toward Lake Michigan through tonight.
   On the southern periphery of this upper low, a warm conveyor
   continues to support regenerative scattered thunderstorms this
   morning across Missouri into Illinois. As these storms gradually
   shift eastward, additional (potentially multiple) rounds of storms
   are expected especially this afternoon into tonight, with increasing
   storms across west-central Kansas this morning potentially related
   to what could be eastward-developing/intensifying storms across
   Kansas into the afternoon near the front. Reference Mesoscale
   Discussion 885 for additional details.

   Meanwhile, to the southwest of the early-day storms, rich low-level
   moisture with surface dewpoints near 70 F will continue to advect
   through eastern Kansas into Missouri on the eastern edge of the
   Plains elevated mixed layer. This will allow for strong
   destabilization into peak heating. A belt of stronger winds along
   southern periphery of the upper low circulation will contribute to
   30-40 kt effective bulk shear, which will be supportive of both
   multicell and some supercell structures. Even with rising upper
   heights, a final round of severe storms could occur as far west as
   southern Kansas/northern Oklahoma this evening as a nocturnally
   increasing low-level jet impinges on the frontal zone.

   ...Eastern Iowa, northern/central Illinois, southern Wisconsin...
   Multiple corridors of early-day showers/thunderstorms to the
   southwest of the region provides some uncertainty regarding
   destabilization later today, but at least modest surface-based
   destabilization is possible this afternoon within a relatively
   narrow moisture-rich warm sector near/just ahead of a weak surface
   low. Deep-layer shear is likely to gradually strengthen through the
   afternoon (upwards of 35-45 kt) and support the possibility of
   supercells. Presuming sufficient boundary-layer destabilization
   occurs, aside from hail/wind, the threat will also exist for a few
   tornadoes as storms move northeastward and interact with the warm
   front across far eastern Iowa, northern Illinois and far southern
   Wisconsin this afternoon into early evening.

   ...Southern portions of MO/IL/IN into KY/TN/southwest OH today...
   Linearly organized clusters of storms ongoing from southern portions
   of Missouri and Illinois early this morning may continue to pose an
   isolated hail and/or wind risk this morning. Recent post-dawn trends
   are for some increased organization and trend of upscale growth
   particularly across southeast Missouri. Aided by a belt of modestly
   enhanced westerlies on the southern periphery of the Upper Midwest
   upper low, it seems plausible that this activity may continue
   east-southeastward through the afternoon from southern portions of
   Illinois/Indiana as well as Kentucky and Tennessee in conjunction
   with a diurnally destabilizing boundary layer. The scenario appears
   to warrant a Slight Risk upgrade for mostly a wind damage concern.

   ...Parts of Georgia and the Carolinas...
   A moist environment and thinning cloud cover will allow for moderate
   destabilization and a subsequent development/intensification of
   storms in areas along and southwest of a
   northwest/southeast-oriented front. Although severe storms may not
   be as widespread as yesterday, at least isolated instances of
   microburst-related wind damage could occur this afternoon into early
   evening as storms spread generally southeastward across the region.

   ...Western/central Dakotas...
   Storms are expected to develop initially across the western Dakotas
   by mid/late afternoon along an eastward-advancing cold front.
   Moderate instability and steep lapse rates with inverted-V boundary
   layers will support isolated instances of downburst winds and hail,
   although a non-supercell-related brief tornado cannot be ruled out
   mainly with the initial development along the front. While the
   overall severe-related scenario currently appears marginal/isolated,
   the region will continue to be reevaluated for a possible
   categorical Slight Risk.

   ..Guyer/Marsh.. 06/26/2018

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