Aug 19, 2017 1300 UTC Day 1 Convective Outlook
Updated: Sat Aug 19 12:16:31 UTC 2017 (20170819 1300Z Day 1 shapefile | 20170819 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170819 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 26,517 249,994 Kearney, NE...North Platte, NE...Hastings, NE...Lexington, NE...
MARGINAL 112,127 12,398,052 Columbus, OH...Pittsburgh, PA...Lincoln, NE...Akron, OH...Parma, OH...
Probabilistic Tornado Graphic
20170819 1300 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20170819 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 24,513 241,137 Kearney, NE...North Platte, NE...Hastings, NE...Lexington, NE...
5 % 114,223 12,349,330 Columbus, OH...Pittsburgh, PA...Lincoln, NE...Akron, OH...Parma, OH...
Probabilistic Large Hail Graphic
20170819 1300 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 26,582 248,818 Kearney, NE...North Platte, NE...Hastings, NE...Lexington, NE...
5 % 112,094 12,337,103 Columbus, OH...Pittsburgh, PA...Lincoln, NE...Akron, OH...Parma, OH...
   SPC AC 191216

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0716 AM CDT Sat Aug 19 2017

   Valid 191300Z - 201200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS
   AFTERNOON INTO EARLY TONIGHT FOR PARTS OF CENTRAL NE AND NORTHERN
   KS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   NE/KS SLIGHT RISK AREA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   FROM EASTERN OH TO CENTRAL PA...

   ...SUMMARY...
   Scattered severe thunderstorms are possible across parts of Nebraska
   and Kansas late this afternoon and through the evening.  Isolated
   severe storms are possible from Ohio into central Pennsylvania
   during the afternoon and ending by the early evening.

   ...Central Plains area this afternoon through tonight...
   Lee cyclogenesis is expected later today across the central High
   Plains, along the southern fringe of the stronger mid-upper
   westerlies.  This will induce strengthening low-level southerly flow
   and associated northward moisture transport from KS/OK to NE by this
   afternoon.  Strong surface heating near the weak lee cyclone/trough
   and along the west edge of the returning moisture will lead to
   weakening convective inhibition by mid-late afternoon.  Near this
   same time, a low-amplitude shortwave trough (over south central WY
   this morning) will reach western NE, and thunderstorm development is
   expected by late afternoon.

   A thermodynamic environment characterized by steep low-midlevel
   lapse rates, MLCAPE of 2000-3000 J/kg, and DCAPE approaching 1500
   J/kg will favor storms with both strong updrafts and downdrafts. 
   Effective bulk shear near 30 kt will favor some marginal supercell
   structures early in the storm evolution.  Upscale growth into a
   cluster is expected this evening/early tonight as a result of storm
   mergers/interactions, as well as increasing low-level warm advection
   with a strengthening low-level jet.  A few large hail and
   strong/damaging outflow instances can be expected this evening into
   early tonight, prior to storms slowly weakening by 04-06z. 

   ...Eastern OH to central PA this afternoon...
   A pronounced midlevel trough over the mid MS and lower OH Valley
   regions will progress eastward to the central Appalachians by this
   evening.  In the wake of weak morning convection, scattered
   thunderstorms will form in advance of the midlevel trough and along
   a diffuse surface front early this afternoon across eastern
   OH/northwestern PA, and then spread eastward across central PA
   through the afternoon.  Residual boundary layer dewpoints in the 60s
   beneath relatively cool midlevel temperatures (-12 C at 500 mb), as
   well as surface heating in cloud breaks, will contribute to MLCAPE
   of 500-1000 J/kg this afternoon.  With midlevel westerly flow and
   effective bulk shear near 30 kt, a few organized clusters could
   produce strong outflow gusts and marginally severe hail.

   ...NC coast this afternoon...
   Scattered thunderstorm development is expected this afternoon along
   a surface trough/weak cold front across coastal NC, aided by local
   sea breeze circulations.  The 12z MHX sounding revealed rather poor
   lapse rates and modest DCAPE around 600 J/kg, despite MLCAPE near
   2500 J/kg.  Though an isolated downburst cannot be ruled out, the
   overall damaging-wind threat appears too low to introduce a 5% wind
   probability area.

   ..Thompson/Dial.. 08/19/2017

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z