SPC AC 221937

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0237 PM CDT Wed Jul 22 2020

   Valid 222000Z - 231200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   THE MID ATLANTIC REGION INTO SOUTHERN NEW ENGLAND...

   ...SUMMARY...
   Strong to severe thunderstorms producing damaging wind gusts are
   expected to continue this afternoon and evening across the
   Mid-Atlantic to portions of western New England.

   ...20Z Update...

   ...Southern New England into Northern Mid-Atlantic...
   Scattered thunderstorms will increase in coverage and
   intensity through the afternoon across southern New England. Strong,
   locally damaging gusts will be possible with these storms into this
   evening. Severe Thunderstorm Watch 394 was recently issued to cover
   this severe potential.

   Farther south, ongoing convective line will continue to move
   eastward across northern VA and into the Delmarva over the next
   several hours. Strong instability and steep low-level lapse rates
   downstream suggest the damaging wind gusts will continue to be a
   threat within this cluster. MCD 1315 was recently issued discussing
   this area in more detail. 

   ...Northern Great Basin...
   Scattered, high-based thunderstorm development is expected to
   increase over the next few hours. These storms will pose an isolated
   risk for strong downburst winds and perhaps severe hail.

   ...FL...
   TBW VAD profile shows deep southeasterly flow between 1 and 6 km,
   with a similar signal showing up at TLH and EVX. These winds coupled
   with steep low-level lapse rates will continue to support gusty
   downburst winds as storms continue westward/northwestward across the
   FL Big Bend into the Panhandle.

   ...NE/KS...
   Potential still exists for the development of a storm or two amid
   the modest low-level convergence and continued air mass
   destabilization. If storms can form, conditions are favorable for
   supercell development, with an attendant risk for large hail and
   gusty winds.

   ..Mosier.. 07/22/2020

   .PREV DISCUSSION... /ISSUED 1047 AM CDT Wed Jul 22 2020/

   ...VA to western New England...
   Moderately strong westerly mid-level winds are present today across
   the Great Lakes region into the northeast states.  Ample low-level
   moisture has advected northward across the region, with dewpoints
   now in the 70s from southeast NY/NJ southward.  Meanwhile, strong
   daytime heating is occurring over this corridor, resulting in strong
   afternoon CAPE values and steep low-level lapse rates.  Present
   indications are that storms will intensify by early afternoon over
   the mountains of eastern WV/central PA and spread eastward toward
   the Mid-Atlantic coast.  The stronger storm clusters will be capable
   of gusty/damaging winds and perhaps hail. Please refer to MCD #1310
   for further details.

   The evolution farther north in northern PA/southern NY is more
   uncertain due to abundant clouds that are overspreading the area
   from the west.  This area has the strongest winds aloft and large
   scale forcing, so a conditional risk of severe storms persists if
   deep convection can develop.  Chose not to modify the ongoing
   forecast due to the conditional threat, but confidence in severe
   storms has diminished somewhat in parts of north-central PA and
   south-central NY.

   ...OH Valley...
   A weak elongated upper trough extends from central MO into parts of
   IL/IN/OH.  Ample moisture and moderate instability will reside to
   the south of the trough, and most CAM solutions indicate scattered
   thunderstorm development will occur.  Wind fields in this zone are
   relatively weak, which should result in rather disorganized
   convection.  Nevertheless, the stronger cores may produce gusty
   winds.

   ...NE/KS...
   Model guidance continues to provide confidence in a small cluster of
   thunderstorms developing this evening over southwest NE and
   northwest KS.  This is likely due to a remnant outflow boundary and
   strong surface heating.  If storms can form, forecast soundings show
   steep mid-level lapse rates and favorable deep-layer shear for a
   supercell or two capable of hail and gusty winds.  

   ...Northern Great Basin...
   Scattered thunderstorms are expected to develop this afternoon over
   much of northern NV, southeast ID, southwest OR, into northwest CA
   as moisture wraps around an upper low near SFO.  
   Southerly deep-layer flow of 20-30 knots over much of NV and
   adjacent areas, along with a deeply-mixed boundary layer, will
   result in conditions favorable for strong outflow winds from the
   more intense high-based storms.

   ...FL...
   20-30 knot southeasterly low and mid level winds are indicated today
   over the western Gulf of Mexico and parts of FL.  Strong heating is
   occurring over the FL Panhandle where dewpoints in the mid 70s will
   yield ample CAPE this afternoon.  Thunderstorms are expected to form
   over the northwest peninsula and spread into the panhandle later
   today.  Steep low-level lapse rates and ambient low level winds will
   help to pose a risk of gusty winds in the stronger storms.

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