SPC AC 190730

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0230 AM CDT Sun Jul 19 2020

   Valid 211200Z - 221200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE MID MISSISSIPPI VALLEY INTO THE MIDWEST AND OHIO VALLEY...THE
   UPPER MIDWEST...AND CENTRAL HIGH PLAINS...

   ...SUMMARY...
   Isolated strong to severe thunderstorms may occur Tuesday from parts
   of the mid Mississippi Valley into the Midwest/Ohio Valley, the
   Upper Midwest, and central High Plains.

   ...Mid Mississippi Valley into the Midwest and Ohio Valley...
   A convectively enhanced mid-level vorticity maximum may be present
   with ongoing storms Tuesday morning somewhere in the vicinity of the
   mid MS Valley. This feature should track northeastward across parts
   of the Midwest into the OH Valley through the day. There is
   uncertainty regarding how quickly rich low-level moisture will
   return northward ahead of this weak perturbation. Regardless, it
   appears probable that sufficient destabilization of the warm sector
   will occur, and storms that develop in association with the
   vorticity maximum may acquire some organization given 25-30 kt of
   mid-level flow. Damaging winds would probably be the main threat
   with any clusters or short line segments moving northeastward across
   these regions through Tuesday evening.

   ...Upper Midwest...
   A shortwave trough initially over the northern Plains is forecast to
   move eastward across the Upper Midwest through the period. A weak
   surface low should also develop slowly eastward across this region.
   It appears that sufficient low-level moisture will be present ahead
   of these features to support weak to potentially moderate
   instability by Tuesday afternoon across parts of MN and perhaps
   western WI. Mid-level westerly flow is forecast to be fairly strong
   (35-50 kt), and organized storms may move eastward across MN/WI
   along or ahead of a cold front through Tuesday evening. Uncertainty
   remains regarding the degree of destabilization, which will impact
   the overall severe risk. Have opted to include 5% severe
   probabilities for now, with potential for an upgrade in later
   outlooks pending better model agreement on forecast instability.

   ...Central High Plains...
   Low-level upslope flow appears likely to occur Tuesday across parts
   of the central High Plains to the north of a weak surface boundary.
   Convection that initially forms over the higher terrain should
   spread eastward with modest west-northwesterly flow present at mid
   levels. This activity should encounter at least a moderately
   unstable airmass across parts of eastern WY/northeastern CO into
   western NE and vicinity. Although flow through mid levels is not
   forecast to be particularly strong, it will veer with height
   considerably. This veering should support sufficient effective bulk
   shear coupled with the moderate instability to support isolated
   strong to severe storms. This convection may spread
   east-southeastward through Tuesday evening while still posing some
   severe threat.

   ..Gleason.. 07/19/2020

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   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z