SPC AC 220559

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1259 AM CDT Wed May 22 2019

   Valid 221200Z - 231200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTHEAST OKLAHOMA...SOUTHEAST KANSAS AND WESTERN TO CENTRAL
   MISSOURI...

   ...SUMMARY...
   Strong to severe thunderstorms associated with a few tornadoes,
   large hail and wind damage will be likely from central and
   northeastern Oklahoma into southeast Kansas and western Missouri
   late this afternoon into the evening. Other marginally severe
   thunderstorms will be possible across parts of the mid to upper
   Mississippi Valley, southern High Plains and Lower Great Lakes
   region.

   ...Oklahoma/Southeast Kansas/Missouri/Far Northwest Arkansas...
   Southwest mid-level flow will be in place across the southern and
   central Plains today. At the surface, a warm front will surge
   northward into northern Oklahoma and southeastern Kansas as moisture
   advection takes place across the southern Plains. Surface dewpoints
   in the lower 70s F will overspread much of Oklahoma, contributing to
   strong destabilization by afternoon. The models including the NAM,
   GFS, HRRR and most of the CAMs are now initiating thunderstorms
   along a corridor from near the OKC Metro northeastward to north of
   Tulsa around 21Z. Some uncertainty exists concerning this scenario.
   The uncertainty is mainly due to the rising heights and limited
   large-scale ascent. However, lift associated with the nose of the
   low-level jet may be enough to initiate convection during the late
   afternoon.

   The environment should be characterized by moderate to strong
   instability (MLCAPE of 3000 to 4000 J/kg) and strong deep-layer
   shear (0-6 km shear of 45 to 55 kt). In addition, 0-3 km
   storm-relative helicities are forecast to peak around 400 m2/s2
   along and to the west of the low-level jet. For this reason,
   supercells with tornado potential are possible in central and
   northeastern Oklahoma into southeast Kansas late this afternoon. A
   significant tornado may occur from near Tulsa northward into far
   southeast Kansas where the strongest low-level shear is forecast
   during the early evening. Supercells will also be capable of
   producing large hail and wind damage. Hailstones of greater than 2
   inches in diameter will be possible with the strongest of
   supercells. A cluster of severe storms is forecast to move
   northeastward into west-central Missouri during the evening where a
   couple tornadoes, large hail and wind damage will also be possible.

   ...Southern High Plains...
   Southwest mid-level flow will be in place across the southern Plains
   today as a moist airmass advects quickly northwestward. The western
   edge of the most airmass is forecast to move from western Oklahoma
   across west Texas during the evening. Although large-scale ascent is
   forecast to be limited, low-level convergence may become strong
   enough for isolated cell initiation to the east of the retreating
   dryline. In the case that a storm can develop, the instability along
   with moderate deep-layer shear and steep mid-level lapse rates would
   be sufficient for hail and isolated damaging wind gusts. 

   ...Lower Great Lakes...
   An upper-level ridge will be in place today across the Northeast
   with west-southwest mid-level flow over the Ohio Valley and Great
   Lakes region. At the surface, southerly winds will advect a moist
   airmass into Ohio during the afternoon. Although large-scale ascent
   will be limited, increasing low-level convergence along the
   instability axis may be enough for isolated thunderstorm development
   mainly in Ohio. Moderate deep-layer shear and steep low-level lapse
   rates are forecast to be sufficient for marginally severe wind gusts
   and hail.

   ..Broyles/Wendt.. 05/22/2019

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