SPC AC 090600

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Sat May 09 2020

   Valid 101200Z - 111200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS FAR SOUTH
   FLORIDA/FLORIDA KEYS AND THE OH VALLEY...

   ...SUMMARY...
   A few strong, possibly severe, thunderstorms are possible across far
   south Florida and the Florida Keys as well as over portions of the
   Ohio Valley.

   ...Synopsis...
   Broad upper troughing will be maintained from the northern Plains
   into the Northeast states throughout the period, aided by a series
   of shortwave troughs progressing from the northern Plains through
   the OH Valley. Surface low associated with the lead shortwave is
   forecast to move eastward across the northern portions of the OH
   Valley into the Northeast. Cold front attendant to this low will
   extend from northern IL southwestward into the southern TX Panhandle
   early Sunday. Northern/eastern portion of this front will remain
   progressive while the southern/western portion of becomes diffuse
   amidst southerly return flow. This reinforcing push of cold
   continental air over the eastern CONUS will keep the favorable
   low-level moisture relegated to the FL Peninsula while
   southerly/southeasterly winds across the southern Plains/southern
   High Plains will support modest moisture return.

   Farther west, a low-amplitude shortwave trough will move into the
   Four Corners, interacting with the seasonally moist air mass over
   the region to create scattered thunderstorms. Most guidance suggests
   precipitable water values across AZ between 0.75 and 1 inch, which
   would be near-record values for the month of May. Instability will
   be limited but high-based storms and a deeply mixed boundary layer
   may contribute to a few strong gusts.

   ...Far South FL/FL Keys...
   Numerous thunderstorms will likely be ongoing or approaching far
   south FL and the FL Keys early Sunday morning, ahead of an
   approaching shortwave trough. A predominantly multicell mode is
   anticipated, but veering wind profiles with height and modest
   instability may support a few stronger storms capable of damaging
   downburst winds. 

   ...OH Valley...
   Strong forcing for ascent is anticipated across portions of IN and
   OH as a shortwave trough moves through, with the attendant surface
   low and cold front just ahead of it. Low-level moisture will be
   relatively modest and surface temperatures mild, but steep mid-level
   lapse rates will still result in enough buoyancy to support
   thunderstorms. Generally low-topped storms are anticipated, but
   strong mid-level flow will support enough vertical shear for
   potentially organized updrafts capable of strong downbursts and/or
   hail.

   ...Southern High Plains...
   Upslope flow is anticipated across the southern High Plains on
   Sunday. Much of the region will be displaced north of the better
   low-level moisture, but convergence along the lee trough and/or cold
   front amidst deep boundary-layer mixing may still result in
   convective initiation. Vertical shear is strong enough such that any
   persistent storm may organize into a supercell. Uncertainty
   regarding convective initiation and overall storm coverage is high,
   precluding any severe probabilities with this outlook.

   ..Mosier.. 05/09/2020

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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z