SPC AC 290722

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0222 AM 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,
   accompanied by at least some risk for severe weather.

   ...Synopsis...
   Models indicate that a highly amplified mid/upper flow regime will
   continue to evolve during this period.  This likely will 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 through the Canadian Yukon and
   Northwest Territories.

   While larger-scale troughing, including the remnants of a
   significant mid-level low, gradually pivot northward and eastward
   across the northeastern Pacific, into the British Columbia and
   Pacific Northwest coast, another significant trough is forecast to
   slowly dig across Hudson Bay, Manitoba and northwest Ontario, to the
   east of the ridging.  Weakening downstream troughing is expected to
   begin shifting east of the north Atlantic coast.

   Within a separate, weaker branch of westerlies, east of the 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 migrate across the Ozark
   Plateau into Mid South vicinity, Friday through Friday night.

   While downstream mid-level ridging builds across the southern into
   middle Atlantic Seaboard, in lower latitudes, a developing tropical
   storm may migrate northeast of Cuba, toward southern Florida.

   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...
   The convectively generated or enhanced lower/mid tropospheric
   vorticity center, and a southward advancing convective outflow
   boundary/surface cold front, may provide focus for vigorous
   thunderstorm development Friday afternoon and evening.  Details are
   still rather unclear, and a faster surging outflow could adversely
   impact severe weather potential over a considerable area.  

   However, a belt of 30-40 kt southwesterly to westerly flow in the
   850-500 mb layer, associated with the cyclonic circulation, coupled
   with high boundary-layer dew points (and precipitable water)
   supportive of moderately large CAPE, may enhance potential for
   thunderstorms capable of producing damaging wind gusts while
   spreading across the Ozark Plateau/Mid South vicinity.  A couple of
   tornadoes may also not be out of the question.

   Meanwhile, residual, steeper lower/mid tropospheric lapse rates and
   favorable shear beneath 30+ kt northwesterly mid-level flow may
   contribute to potential for marginally severe hail and wind across
   the plains of eastern New Mexico into western Texas.

   ..Kerr.. 07/29/2020

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