SPC AC 150742

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0242 AM CDT Wed Jul 15 2020

   Valid 171200Z - 181200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE DAKOTAS INTO WESTERN MN...

   ...SUMMARY...
   Severe thunderstorms are expected across portions of the northern
   Plains on Friday afternoon and evening. At this time, damaging wind
   gusts and hail appear to be the primary hazards associated with this
   activity.

   ...Northern Plains vicinity...

   An upper ridge centered over eastern portions of the northern Plains
   will quickly shift eastward on Friday as a shortwave trough over the
   northern Rockies ejects eastward across the Dakotas. A second
   embedded shortwave may also eject across the central Plains toward
   the mid-MO Valley, but this is less certain. Regardless, a band of
   strong westerlies will overspread the Plains while strengthening
   southerly low level flow transports rich boundary layer moisture
   northward. A surface low is forecast to be located over SK, with a
   trailing cold front extending southward near the MT/ND border
   vicinity by midday. Thunderstorms are expected to develop along the
   surface boundary in a strongly sheared, very unstable airmass.
   Supercell wind profiles will support organized cells capable of
   large hail and strong gusts. If cells remain discrete, a couple of
   tornadoes also will be possible near any developing surface low
   along the frontal wave across eastern ND/SD into western MN.
   Forecast guidance indicates a strong southwesterly low level jet
   developing during the evening, and upscale growth into a bowing MCS
   will be possible as convection spreads eastward into MN. 

   Additional severe storms could develop further south across parts of
   NE, as some guidance depicts another shortwave impulse ejecting from
   the central Rockies into the central Plains. However, capping will
   likely increase with southward extent and forcing will be weaker.
   Given this uncertainty, will keep the slight risk confined to the
   northern Plains where the stronger upper trough and surface front
   will provide strong forcing and a more focused threat.

   ...Mid-South to the Mid-Atlantic...

   A surface cold front will push offshore the Northeast and
   Mid-Atlantic coast by around midday Friday. The southwestern extent
   of the surface boundary will become ill-defined across the
   Mid-South. However, a very moist and moderately unstable airmass
   will be in place. Ongoing convection and cloud cover my limit strong
   destabilization, and weakening vertical shear is expected as an
   upper trough lifts northeast early in the period. Nevertheless, a
   few strong storms could produce locally damaging gusts. This
   somewhat limited parameter space and the uncertainty related to
   ongoing convection at the beginning of the period, will preclude
   severe probabilities at this time.

   ..Leitman.. 07/15/2020

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