SPC AC 301957

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0257 PM CDT Thu Jul 30 2020

   Valid 302000Z - 311200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
   OKLAHOMA/NORTH TEXAS EAST TO WESTERN TENNESSEE AND NORTHERN
   MISSISSIPPI...

   ...SUMMARY...
   Severe thunderstorms capable of producing damaging winds and hail
   are expected from western north Texas across parts of Oklahoma and
   Arkansas during the late afternoon and evening. Locally damaging
   winds are also possible from Kentucky/Tennessee into parts of the
   Northeast this afternoon into tonight.

   ...20z Update...
   No significant changes were made to the previous outlook. Clusters
   of thunderstorms were located along and south of a stationary front
   stretching from southern New England southwest through the Ohio
   Valley and Southern Plains. A series of weak mid-level perturbations
   within westerly flow aloft will help to maintain storms into the
   evening hours.  Across the OK/western North Texas portion of the
   Slight Risk area, latest mesoanalysis depicts decreasing CINH as
   heating continues in the vicinity of a remnant outflow
   boundary/confluence zone, and an increase in thunderstorm
   coverage/intensity is anticipated over the next few hours.

   ..Bunting.. 07/30/2020

   .PREV DISCUSSION... /ISSUED 1135 AM CDT Thu Jul 30 2020/

   ...Southern Great Plains to the Mid-South...
   A shortwave trough moving southeastward across the western Kansas
   area will shift into/across Oklahoma as the period progresses.  At
   smaller scales, several convectively induced disturbances are
   shifting eastward across the Ozarks and Mid South regions, with a
   pronounced zone of outflow arcing from central Arkansas
   west-southwestward into North Texas.  Convection is forecast to
   gradually increase in coverage this afternoon in the vicinity of
   these disturbances/outflow, where a moist boundary layer combines
   with diurnal heating to allow moderate destabilization.  With
   enhanced/weakly cyclonic westerly mid-level flow across this region
   sufficient to support multicell organization, a few stronger storms
   will be capable of producing gusty/locally damaging winds.  In light
   of this, SLGT risk is being expanded eastward into western Tennessee
   and far northern Mississippi, given potential for slightly greater
   storm coverage than earlier anticipated near the MCV/outflow moving
   into eastern Arkansas a this time.

   Meanwhile, as the main upper vort max approaches Oklahoma from the
   northwest, late afternoon/early evening storm development is
   expected.  The primary zone of development is expected in the
   vicinity of the Red River, over southern Oklahoma/North Texas, near
   the remnant outflow, with secondary development farther north near
   the ill-defined cold front crossing northwestern Oklahoma.  Strong
   heating combined with a moist boundary layer will permit 1500 to
   3000 J/kg mixed-layer CAPE to evolve, fueling the development, and
   enhanced (40-plus kt) mid-level west-northwesterly flow will support
   organized storms and possibly upscale/semi-linear evolution.  Large
   hail will be possible initially in addition to locally damaging
   winds, with risk likely evolving toward mainly wind as storms spread
   eastward across Oklahoma/north Texas toward Arkansas this evening.

   ...KY/TN to the Appalachians...
   An MCV over southern IL will continue shifting eastward, which --
   combined with continued destabilization of the boundary layer, will
   permit an increase in convection to continue from KY/TN eastward
   across WV and vicinity.  Though weak lapse rates should limit
   overall severe risk, moderate mid-level westerlies
   should support scattered multicell clusters capable of producing
   locally damaging winds. Additional rounds of isolated damaging winds
   may also linger this evening into tonight with convection that
   spreads east into/across this area.

   ...PA to southern New England...
   A weak cool front will focus isolated thunderstorm across this
   region, as modest destabilization continues.  Strong flow aloft
   should support a few organized/rotating storms, capable of producing
   locally damaging winds and small hail.  Storm coverage will likely
   remain limited/isolated, thus precluding slight risk upgrade despite
   favorably strong deep-layer flow.

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