SPC AC 141613

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1113 AM CDT Mon May 14 2018

   Valid 141630Z - 151200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS CENTRAL
   APPALACHIANS AND LOWER MID-ATLANTIC STATES...

   ...SUMMARY...
   Potential exists for a derecho with widespread damaging winds across
   parts of the Central Appalachians and Lower Mid-Atlantic States this
   afternoon into early evening. A broad swath of scattered severe
   storms producing large hail and damaging wind is expected from the
   southern Great Plains across the Lower Missouri Valley and Midwest
   late afternoon and evening.

   ...Central Appalachians and Lower Mid-Atlantic States...
   A pair of elevated MCSs are ongoing along the OH/PA border and
   west-central OH. Robust diabatic heating is occurring to the south
   and east of the composite outflow/front to a persistent stratus deck
   over the Piedmont and Coastal Plain of PA to northeast VA. The
   northeast extent of a massive EML plume will contribute to MLCAPE of
   1500-2500 J/kg amid low to mid 60s surface dew points. On the
   southern periphery of enhanced mid-level westerlies, an increasingly
   organized line with embedded bows may develop. This will probably
   move east, before tending to evolve southeast after crossing the
   Appalachians this afternoon. Although CAM simulations vary markedly
   across the region, potential exists for a derecho with widespread
   damaging winds and have increased probabilities accordingly. An
   upgrade to Moderate risk may occur if even greater damaging wind
   coverage becomes evident with the 20Z outlook. The MCS should
   eventually weaken in southeast VA as it becomes increasingly
   divorced from stronger deep-layer shear.

   ...Southern Great Plains to Lower MO Valley...
   A broad moderate to strongly unstable air mass will develop this
   afternoon southeast of the quasi-stationary front in KS/MO and east
   of the southern Great Plains dryline. Frontal convergence, dryline
   mixing, and weak impulses embedded within the southwesterly flow
   regime aloft should contribute to the initiation of storms from west
   TX through parts of OK, KS, and MO by late afternoon. Weak to modest
   vertical shear over the southern Great Plains portion will yield
   predominant multicell and outflow-dominated storms with risks for
   severe wind and hail. Over parts of KS/MO, slightly stronger
   deep-layer shear along with an MCV drifting across parts of eastern
   KS should support numerous storms and potentially greater large
   hail/damaging wind coverage. Hodographs still appear unremarkable,
   but will monitor this region for a possible upgrade to Enhanced risk
   in the 20Z outlook.

   ...Mid-MS Valley and Midwest...
   In the wake of early-day MCSs and upstream development in KS/MO,
   convective evolution late afternoon and evening in this region has
   lower confidence. Nevertheless, destabilization should be most
   pronounced across the Mid-MS Valley with scattered storm development
   near the quasi-stationary front and residual outflow. This activity
   may evolve into additional MCSs this evening with severe hail and
   damaging wind threats.

   ...Eastern CO vicinity...
   Upslope east-northeast low-level flow will persist beneath moderate
   southwesterly winds aloft contributing to 45+ kt effective bulk
   shear. The atmosphere is expected to become marginally unstable
   along the Front Range and scattered storms will likely develop by
   late afternoon to early evening. This environment should support a
   couple supercells with large hail the main threat. The weak buoyancy
   remains a potential limiting factor, but will continue to monitor
   for a possible Slight risk in the 20Z outlook.

   ...East-central FL Peninsula...
   A small corridor of enhanced low-level shear persists within this
   region with 0-1 km values near 25 kt per Melbourne VAD wind profile.
   Some potential will exist for a brief tornado during the next few
   hours with scattered storms emanating north from south FL. Later
   this afternoon, low-level winds will veer and reduce available SRH,
   mitigating a tornado risk.

   ..Grams/Coniglio.. 05/14/2018

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