Aug 15, 2017 1630 UTC Day 1 Convective Outlook
Updated: Tue Aug 15 16:31:31 UTC 2017 (20170815 1630Z Day 1 shapefile | 20170815 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170815 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 75,980 634,526 Grand Island, NE...Kearney, NE...North Platte, NE...Norfolk, NE...Hastings, NE...
MARGINAL 321,697 15,017,885 Oklahoma City, OK...Virginia Beach, VA...Omaha, NE...Tulsa, OK...Wichita, KS...
Probabilistic Tornado Graphic
20170815 1630 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
2 % 18,096 181,668 Norfolk, NE...Columbus, NE...Yankton, SD...
Probabilistic Damaging Wind Graphic
20170815 1630 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 % 75,994 634,328 Grand Island, NE...Kearney, NE...North Platte, NE...Norfolk, NE...Hastings, NE...
5 % 296,431 14,597,302 Oklahoma City, OK...Virginia Beach, VA...Omaha, NE...Tulsa, OK...Wichita, KS...
Probabilistic Large Hail Graphic
20170815 1630 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 % 62,595 514,453 Grand Island, NE...Kearney, NE...North Platte, NE...Norfolk, NE...Hastings, NE...
5 % 304,003 9,996,761 Oklahoma City, OK...Omaha, NE...Tulsa, OK...Wichita, KS...Lincoln, NE...
   SPC AC 151631

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1131 AM CDT Tue Aug 15 2017

   Valid 151630Z - 161200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
   CENTRAL PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A LARGER
   PART OF THE PLAINS STATES....

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
   NEW YORK INTO NORTHERN NEW ENGLAND...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER SOUTHEAST
   VIRGINIA AND CENTRAL/EASTERN NORTH CAROLINA...

   ...SUMMARY...
   Isolated to scattered severe storms are most likely across parts of
   the Great Plains, beginning late afternoon and continuing through
   tonight.  Other strong to isolated severe storms will be possible
   this afternoon from northeast New York into northern New England,
   and from southeast Virginia into parts of central/eastern North
   Carolina.

   ...Great Plains...
   A complex thunderstorm scenario is expected as several features
   aloft advance into plains region and interact with multiple
   low-level boundaries.  Water vapor imagery shows a primary trough
   moving across the Rockies with embedded vorticity maxima over
   Wyoming and northern Arizona, and a weaker downstream vorticity max
   over southeast Colorado.  These features will enhance large-scale
   ascent over parts of the plains this afternoon and tonight and
   promote an increase in thunderstorms by the early-mid afternoon.

   Strong diabatic heating is occurring within a moist air mass from
   extreme southern Nebraska and Kansas into the High Plains over
   eastern parts of Colorado and New Mexico into west Texas.  This will
   gradually weaken the cap, and coupled with ascent from the
   approaching upper vorticity maxima, initiate storms over the High
   Plains by early afternoon.  Stronger vertical shear is expected
   across parts of northwest Kansas into northern Nebraska, and when
   combined with MLCAPE of 2000-3000 J/kg, provide a favorable
   environment for strong-to-severe storm development.  This activity
   is expected to spread eastward/northeastward through the evening
   hours with stronger cells capable of producing large hail and
   damaging wind gusts.  

   Farther south, model guidance including some 12Z CAMs develop
   additional storms over western/central Oklahoma by early afternoon. 
   Although vertical shear is expected to be marginally supportive of
   organized storms, strong instability within a steep lapse rate
   environment may promote a few severe storms during the afternoon
   into the early evening. 

   ...Southeast Virginia into central/eastern North Carolina...
   Water vapor imagery shows a low-amplitude short wave trough
   progressing eastward across the central Appalachians with weak
   ascent spreading across the discussion area this afternoon.  The
   environment is characterized by substantial moisture and
   comparatively weak lapse rates.  20-30 kt westerly winds aloft will
   provide sufficient shear for organized multi-cell storm clusters to
   develop and move eastward this afternoon and early evening.  The
   primary threat will be for localized wind damage with stronger
   convection.

   ...Northern New England...
   A shortwave trough over the Great Lakes will dampen as it rapidly
   progresses across New England. Ahead of this feature and a cold
   front advancing southeast in Quebec, diabatic heating of modest
   boundary-layer moisture characterized by 50s to lower 60s surface
   dew points should foster weak MLCAPE of 500-1000 J/kg. While
   low-level winds should be modest, elongated straight-line hodographs
   could favor a few cells with mid-level updraft rotation, resulting
   in a risk for marginally severe hail and locally damaging winds.

   ..Weiss/Marsh.. 08/15/2017

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z