Apr 30, 2017 1300 UTC Day 1 Convective Outlook
Updated: Sun Apr 30 13:00:54 UTC 2017 (20170430 1300Z Day 1 shapefile | 20170430 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170430 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 31,659 1,651,462 Jackson, MS...Hattiesburg, MS...Meridian, MS...Clinton, MS...Pearl, MS...
SLIGHT 221,613 37,746,831 Chicago, IL...Detroit, MI...Indianapolis, IN...Memphis, TN...Nashville, TN...
MARGINAL 190,006 33,948,582 Columbus, OH...Milwaukee, WI...Cleveland, OH...Pittsburgh, PA...Cincinnati, OH...
Probabilistic Tornado Graphic
20170430 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
10 % 31,659 1,651,462 Jackson, MS...Hattiesburg, MS...Meridian, MS...Clinton, MS...Pearl, MS...
5 % 165,001 23,354,735 Indianapolis, IN...Nashville, TN...New Orleans, LA...St. Louis, MO...Birmingham, AL...
2 % 100,198 21,086,687 Chicago, IL...Memphis, TN...Toledo, OH...Cincinnati, OH...Louisville, KY...
Probabilistic Damaging Wind Graphic
20170430 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 % 209,820 26,057,252 Indianapolis, IN...Memphis, TN...Nashville, TN...New Orleans, LA...Toledo, OH...
5 % 217,893 45,100,533 Chicago, IL...Detroit, MI...Columbus, OH...Cleveland, OH...St. Louis, MO...
Probabilistic Large Hail Graphic
20170430 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 % 235,205 37,327,389 Chicago, IL...Indianapolis, IN...Nashville, TN...New Orleans, LA...St. Louis, MO...
5 % 166,759 27,776,133 Detroit, MI...Columbus, OH...Memphis, TN...Milwaukee, WI...Cleveland, OH...
   SPC AC 301300

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0800 AM CDT Sun Apr 30 2017

   Valid 301300Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   LA/MS/AL...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE GULF
   COAST STATES TO MIDWEST...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE GULF
   COAST STATES TO MIDWEST AND NORTHERN APPALACHIANS...

   ...SUMMARY...
   Severe thunderstorms capable of damaging winds and tornadoes are
   expected today into tonight, especially across the central Gulf
   Coast States. Other severe storms could occur as far north as the
   Midwest and southern Great Lakes region.

   ...Lower MS River Valley/Gulf Coast States...
   A linearly organized broken cluster of storms is ongoing across
   along the LA/MS vicinity, where multiple tornadoes have occurred in
   the pre-dawn hours, and extends southward into south-central LA
   early this morning. These storms will continue to spread
   east-northeastward through the morning/afternoon hours. Although
   high-level winds are not overly strong per regional 12Z soundings, a
   modest but strengthening westerly component aloft in conjunction
   with strong low-level shear, including modestly backed southeasterly
   surface winds, will continue to support a mixed convective mode
   including embedded supercells/mesovortices capable of tornadoes and
   damaging winds. A strong tornado cannot be ruled out. See Mesoscale
   Discussion 611 for additional short-term details. 

   The tornado/damaging wind risk should shift into portions of AL by
   this afternoon, including the possibility of some regenerative
   development later this afternoon into early evening particularly on
   the southern flank of convection/possible outflow amidst moist
   confluent low-level flow. 

   ...Midwest/southern Great Lakes and Ohio Valley...
   Questions exist regarding the extensiveness and likelihood of
   appreciable destabilization later today in a scenario that appears
   otherwise very favorable for severe thunderstorms given ample
   deep-layer/low-level shear. These uncertainties are related to
   extensive convection ongoing early today across the middle MS River
   Valley and lower OH Valley, with an east/northeastward-moving MCV
   also a factor across eastern IL/northern IN today. 

   Ahead of the cold front, gradual destabilization should occur into
   this afternoon along the southern/eastern fringes of ongoing
   precipitation and residual outflows, with the possibility of least
   some damaging wind/marginally severe hail risk developing this
   afternoon. As the upstream trough approaches the region and surface
   low spreads northeastward and deepens, at least a narrow corridor of
   modest destabilization could allow for late afternoon and evening
   increase in fast-moving storms capable of a severe risk.

   ..Guyer/Mosier.. 04/30/2017

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