Aug 19, 2017 0600 UTC Day 1 Convective Outlook
Updated: Sat Aug 19 05:54:07 UTC 2017 (20170819 1200Z Day 1 shapefile | 20170819 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170819 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 19,327 185,493 Kearney, NE...North Platte, NE...Lexington, NE...
MARGINAL 119,487 12,200,168 Columbus, OH...Pittsburgh, PA...Lincoln, NE...Akron, OH...Parma, OH...
Probabilistic Tornado Graphic
20170819 1200 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 1200 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 % 19,216 185,382 Kearney, NE...North Platte, NE...Lexington, NE...
5 % 118,594 11,679,818 Columbus, OH...Pittsburgh, PA...Lincoln, NE...Akron, OH...Parma, OH...
Probabilistic Large Hail Graphic
20170819 1200 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 % 18,942 184,475 Kearney, NE...North Platte, NE...Lexington, NE...
5 % 119,490 12,181,356 Columbus, OH...Pittsburgh, PA...Lincoln, NE...Akron, OH...Parma, OH...
   SPC AC 190554

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1254 AM CDT Sat Aug 19 2017

   Valid 191200Z - 201200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR CENTRAL
   NEBRASKA AND PORTIONS OF NORTHWEST KANSAS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR MUCH OF
   NEBRASKA AND NORTHERN KANSAS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
   OHIO INTO CENTRAL PENNSYLVANIA...

   ...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.

   ...Synopsis...
   Early morning water-vapor imagery shows a vigorous shortwave trough
   over the Midwest and an upstream lower-amplitude disturbance over
   WY.  Both features are forecast to move generally eastward during
   the period and reach the Lower Great Lakes and the central High
   Plains, respectively, by late afternoon.  A surface trough will
   sharpen during the day across the central High Plains as a low
   develops east across Manitoba.  A relatively ill-defined surface
   pattern is forecast across the upper OH Valley with high pressure
   centered over the southern Appalachians.

   ...Central Plains...
   The influence of a mid-level ridge will abate during the day as a
   mid-level vorticity maximum moves into western NE by afternoon. 
   Will tailor this outlook towards a NAM/SREF median moisture
   scenario.  The 00Z GFS is an outlier and is dry biased according to
   early morning surface observations across the central Plains (1-3
   degrees C too low).  The dichotomy in moisture/buoyancy depictions
   by the aforementioned model guidance is apparent during the late
   afternoon.  It seems most probable a corridor of upper 50s-lower 60s
   boundary layer dewpoints will reside across NE/KS.  As the mid-level
   disturbance and associated weak forcing for ascent overspreads the
   warm sector coupled with strong heating eroding convective
   inhibition, isolated thunderstorms are likely by late
   afternoon/early evening.  Very steep surface-500 mb lapse rates
   ranging from 8-9 degrees C/km will favor intense downdrafts with the
   more robust cores.  Veering flow within this same layer with modest
   mid-level westerlies will yield 30-40 kt effective
   shear---sufficient for some storm organization.  Large hail/severe
   gusts may accompany the more intense thunderstorms.  As a southerly
   LLJ strengthens during the evening, a continuation of some
   strong/severe potential may occur farther east into east-central
   NE/north-central KS through the evening. 

   ...OH eastward into central PA...
   A plume of modestly moist low levels is forecast to extend northeast
   across the OH Valley ahead of a potent mid-level impulse.  Weak
   buoyancy will contribute to convective development as early as
   midday over OH.  Forecast soundings suggest some marginal storm
   organization potential.  The primary threats with the stronger
   storms will be localized pockets of damaging gusts and perhaps a few
   updrafts capable of marginally severe hail.  This activity will
   diminish by early evening owing to the loss of instability.

   ..Smith/Gleason.. 08/19/2017

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z