SPC AC 281722

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1222 PM CDT Fri Jun 28 2024

   Valid 291200Z - 301200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM OHIO INTO
   PORTIONS WEST VIRGINIA...MARYLAND...PENNSYLVANIA AND NEW YORK...

   ...SUMMARY...
   Scattered damaging winds and a couple tornadoes are possible on
   Saturday from parts of Ohio into northern West Virginia/Maryland,
   central and western Pennsylvania, and western New York.

   ...Ohio Valley to the Northeast...

   Several vorticity maxima are forecast to migrate across the region
   within an area of enhanced southwesterly flow aloft ahead of the
   main upper shortwave trough progressing from the Upper Midwest to
   the lower Great Lakes. At the surface, low pressure will spread
   east/northeast from the upper Great Lakes into Ontario/Quebec. As
   this occurs, strong theta-e advection on southwesterly low-level
   flow will result in a very moist airmass spreading north/northeast
   from the Midwest into much of the Northeast. Early cloudiness and
   periods of showers may limit diurnal destabilization from eastern PA
   into NY. Pockets of stronger instability will overlap 30-40 kt
   westerly midlevel flow from parts of Ohio into western/central
   PA/NY. While midlevel lapse rates will remain quite poor, sufficient
   effective shear magnitudes amid rich boundary-layer moisture should
   support organized clusters and line segments capable of
   strong/damaging gusts. Vertically veering low-level winds will
   support somewhat enlarged and curved hodographs, with sufficient
   low-level instability and 0-1 km SRH. In addition to damaging gusts,
   a couple of tornadoes also will be possible. 

   A more conditional risk may exist from late evening into the early
   overnight hours across parts of northern NY into VT as the surface
   front impinges on the area and the main upper shortwave trough
   ejects eastward. Strong vertical shear will be in place amid a very
   moist airmass. However, convection may remain elevated given poor
   timing with the diurnal cycle and impacts from daytime convection.
   If convection can become surface-based, damaging gusts will be
   possible. 

   ...OK/KS to the Mid-MS Valley...

   Convection may be ongoing Saturday morning across parts of central
   MO. This activity may weaken during the morning, or slowly
   reintensify during the afternoon along outflow or the
   southward-advancing surface cold front. Additional convection is
   expected to develop along the sagging front across southern
   KS/northern OK during the late afternoon/evening. A couple of
   forward-propagating clusters are possible within this area of modest
   vertical shear, but rich boundary-layer moisture (dewpoints in the
   upper 60s/low 70s F) and moderate to strong instability. Isolated
   severe/damaging gusts and a few instances of hail will be possible
   with this activity. A corridor of higher probabilities may be needed
   in subsequent outlooks if confidence increases in location of better
   organized frontal convection.

   ...Central/Southern High Plains...

   Isolated convection is expected during the evening in a post-frontal
   upslope flow regime. Near 60 F surface dewpoints and steep midlevel
   lapse rates will support a corridor of moderate instability. While
   deep-layer flow will be light, vertically veering wind profiles will
   support 30-40 kt effective shear magnitudes amid a deeply mixed
   boundary-layer. Isolated strong to severe thunderstorms capable of
   strong gusts and hail will be possible.

   ...Northern IL into eastern WI and MI...

   Most forecast guidance is fairly sparse with convection across this
   area on Saturday. However, a very moist and unstable airmass will be
   in place ahead of the east/southeast-advancing cold front, along
   with favorable vertical shear for organized storms. Large-scale
   ascent will remain somewhat weak and ill-timed with the cold front
   progression, and low-level frontal convergence also will be poor.
   Severe probabilities have been adjusted some over the region based
   on low storm coverage and latest trends. However, a conditional
   severe threat will exist if storms develop.

   ..Leitman.. 06/28/2024

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