SPC AC 300455

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1155 PM CDT Wed Jul 29 2020

   Valid 311200Z - 011200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FRIDAY AFTERNOON
   AND EVENING ACROSS PARTS OF THE SOUTHERN GREAT PLAINS INTO THE OZARK
   PLATEAU AND MID SOUTH...

   ...SUMMARY...
   Strong thunderstorms may impact portions of the southern Great
   Plains into the Ozark Plateau and Mid South vicinity Friday
   afternoon and evening, accompanied by at least some risk for severe
   weather.

   ...Synopsis...
   A highly amplified mid/upper flow regime appears likely to  continue
   to evolve across North America through this period.  This is
   expected to include a prominent subtropical high center over the
   Southwest, and ridging within the mid-latitude westerlies to the
   north, across the northern U.S. intermountain region and Rockies
   into the Canadian Yukon and Northwest Territories.

   Within larger-scale troughing upstream of the ridging, across the
   northeastern Pacific, the remnants of a significant mid-level low
   may pivot northward toward the British Columbia coast.  Another
   significant trough is forecast to slowly dig across Hudson Bay,
   Manitoba and northwest Ontario, to the east of the ridging, and 
   weakening downstream troughing may slowly begin accelerating east of
   the north Atlantic coast.

   Within a separate, weaker branch of westerlies, east of the U.S.
   Rockies into the middle and southern Atlantic Seaboard, large-scale
   mid-level troughing may continue to evolve and amplify further,
   along a positively tilted axis roughly across the middle Mississippi
   Valley into the southeastern Great Plains.  A fairly substantial,
   convectively generated or enhanced, lower/mid-tropospheric cyclonic
   circulation evolving within this regime may slowly migrate into and
   through the Ozark Plateau vicinity, Friday through Friday night.

   While downstream mid-level ridging builds across the Southeast into
   the mid Atlantic Seaboard, in lower latitudes, a developing tropical
   storm may migrate northeastward toward, and approach southern
   Florida by late Friday night.

   Highest thunderstorm probabilities are expected to remain generally
   focused with higher moisture content air, along the weaker southern
   branch of the westerlies to the east of the Rockies.

   ...Southern Great Plains into Ozark Plateau/Mid South...
   A corridor of stronger daytime heating ahead of a weak southward
   advancing cold front, likely substantially reinforced by convective
   outflow, is still expected to provide the primary potential focus
   for vigorous thunderstorm development Friday afternoon and evening. 
   This may be aided by forcing for ascent associated with the digging
   mid-level troughing, and the embedded cyclonic circulation center,
   which may be accompanied by a belt of 30-40 kt southwesterly to
   westerly flow in the 850-500 mb layer spreading east of the Red
   River, toward the Mid South.

   With mixed-layer CAPE forecast to increase in excess of 2000 J/kg by
   late afternoon, the ambient vertical vorticity and stronger flow
   near the cyclonic circulation may contribute to the risk for a
   couple of tornadoes with storms across the Arkansas vicinity, in
   addition to locally strong surface gusts aided by heavy
   precipitation loading.  Residual steeper lower/mid tropospheric
   lapse rates to the southwest of the cyclonic circulation may
   contribute to potential for marginally severe wind and hail in
   storms across central Texas.

   ...South Florida...
   Based on the current forecast track of the possible developing
   tropical cyclone, it is not out of the question that at least some
   increase in potential for convection capable of producing tornadoes
   could impact southeast Florida coastal areas prior to 12Z Saturday. 
   However, given the increasing spread in the forecast track of the
   developing storm as it approaches south Florida, among other
   factors, tornado probabilities will be maintained at less than 2
   percent at this time.

   ..Kerr.. 07/30/2020

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