SPC AC 101252

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0752 AM CDT Fri Jul 10 2020

   Valid 101300Z - 111200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   INTO EARLY TONIGHT FROM SOUTHWEST ND ACROSS CENTRAL SD TO NORTHERN
   NE...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS MORNING
   ACROSS NORTH CENTRAL OK...AND TODAY ALONG THE COASTAL AREAS OF NJ TO
   SOUTHERN NEW ENGLAND...

   ...SUMMARY...
   Multiple clusters of severe storms are expected over parts of the
   northern and central Plains this afternoon into tonight, with the
   potential to produce very large hail, damaging winds, and a few
   tornadoes.

   ...Northern/central Plains this afternoon through tonight...
   A midlevel shortwave trough over the northern Rockies will move
   eastward today over MT, and then turn southeastward tonight across
   the northern High Plains, around the northeast periphery of the
   southern Rockies midlevel anticyclone.  An accompanying surface cold
   front will likewise move eastward across MT today, where it will
   encounter richer low-level moisture and larger buoyancy late this
   afternoon/evening from eastern MT into the Dakotas.  MLCAPE at or
   above 2000 J/kg, midlevel lapse rates in excess of 8 C/km, and
   effective bulk shear greater than 40 kt will all favor supercells
   capable of producing very large hail and damaging winds from
   southeast MT into southwest ND and northwest SD by this evening.

   A separate area of severe storm development will be possible today
   farther to the east in SD.  A lead shortwave trough (now over
   northeast WY/southeast MT) will move over central SD this afternoon.
   Ongoing elevated convection (in the zone of ascent preceding the
   midlevel trough) will help reinforce a baroclinic zone across
   central SD, where additional thunderstorm development is possible
   this afternoon.  Locally enhanced low-level moisture and vertical
   shear along this baroclinic zone, in combination with  very steep
   midlevel lapse rates and strong deep-layer vertical shear, will
   favor supercells capable of producing very large hail, damaging
   winds, and a couple of tornadoes.

   The overnight convective evolution is substantially more uncertain,
   from NE into KS.  Either the western SD storms near the cold front,
   or the central SD storms along the reinforced baroclinic zone, could
   grow upscale into an MCS.  MCS motion toward the southeast is
   expected, following the influx of richer moisture along the nose of
   a central Plains low-level jet.  Confidence in any details of MCS
   formation/evolution is relatively low for the overnight period, so
   will maintain the outlook area and will be maintained largely as is.
    
   ...Southern KS/northern OK this morning...
   An ongoing cluster of storms is moving southward into north central
   OK, in a zone of weak low-level warm advection on the southern edge
   of minimal convective inhibition.  Buoyancy (MUCAPE in excess of
   2000 J/kg), midlevel lapse rates (near 8.5 C/km) and wind profiles
   (effective bulk shear of 40-50 kt) will be sufficient to maintain an
   organized storm cluster/supercell through mid morning, with
   weakening expected thereafter.  Isolated large hail will be
   possible, along with damaging winds given DCAPE near 1400 J/kg.

   ...Coastal NJ to southern New England through this evening...
   Tropical storm Fay is forecast to move generally northward today
   near the NJ coast, and continue across southeast NY and western
   MA/CT tonight (please see latest advisories from NHC for additional
   information).  The primary convective band is expected to remain
   north-through-east of the surface center of Fay, and this convective
   band will spread across the NJ coast today, and Long Island/southern
   New England this evening into tonight.  The wind field with Fay is
   not particularly broad or strong, which suggests that there will
   only be a narrow (and somewhat marginal) window of opportunity for
   mini supercells in the zone where the stronger low-level shear
   overlaps the low-mid 70s boundary-layer dewpoints and at least weak
   surface-based buoyancy.

   ...Southeast Lower MI/northwest OH today...
   A broken band of storms should strengthen from midday into early
   afternoon from southeast Lower MI into northwest OH, in advance of a
   midlevel trough and near an associated surface cold front.  Isolated
   strong/damaging downburst winds will be possible with these storms
   this afternoon.

   ..Thompson/Broyles.. 07/10/2020

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