Apr 21, 2019 2000 UTC Day 1 Convective Outlook
Updated: Sun Apr 21 19:38:24 UTC 2019 (20190421 2000Z Day 1 shapefile | 20190421 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20190421 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 102,372 2,659,594 Omaha, NE...Lincoln, NE...Sioux City, IA...Council Bluffs, IA...Bellevue, NE...
Probabilistic Tornado Graphic
20190421 2000 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
20190421 2000 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
5 % 102,266 2,651,120 Omaha, NE...Lincoln, NE...Sioux City, IA...Council Bluffs, IA...Bellevue, NE...
Probabilistic Large Hail Graphic
20190421 2000 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
5 % 64,359 737,085 Grand Island, NE...Kearney, NE...Norfolk, NE...Hastings, NE...Columbus, NE...
   SPC AC 211938

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0238 PM CDT Sun Apr 21 2019

   Valid 212000Z - 221200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE CENTRAL PLAINS...

   ...SUMMARY...
   Marginally severe hail or wind is possible across parts of the
   central Plains this afternoon and evening, mainly from northern
   Kansas into Nebraska.

   ...20z Update - Central Plains into tonight...

   Widely scattered thunderstorms have developed over the eastern CO
   Plains this afternoon. Strong surface heating and increasing ascent
   has reduced inhibition across the area, with steep midlevel lapse
   rates contributing to weak instability.  Boundary layer moisture
   remains scant with surface dewpoints in the mid 30s to mid 40s and
   convection is expected to remain high-based. Given the rather dry
   boundary layer and very steep sfc-3km lapse rates, strong wind gusts
   are possible. Steep lapse rates and marginal effective bulk shear
   around 25-35 kt also will support marginally severe hail in stronger
   cells. As more substantial forcing overspreads the region the region
   this evening, convection should increase east/northeast along the
   surface cold front into portions of KS/NE. Ongoing forecast remains
   on track and no changes have been made to the Marginal risk area.

   ..Leitman.. 04/21/2019

   .PREV DISCUSSION... /ISSUED 1119 AM CDT Sun Apr 21 2019/

   ...Central Plains late this afternoon into tonight...
   A series of low-amplitude midlevel troughs will eject
   east-northeastward from NM/CO to the mid MO Valley, downstream from
   an amplifying trough over the lower CO Valley.  Modest low-level
   moisture return is underway from the western Gulf of Mexico to the
   southern/central Plains.  The moistening will occur beneath a warm
   elevated mixed layer, and much of the warm sector will remain capped
   through the period.  Strong surface heating/deep mixing and
   low-level ascent from near a lee cyclone along the CO/KS border
   northeastward along a cold front into NE should support thunderstorm
   development this afternoon/evening.  MLCAPE of 500-1000 J/kg with
   steep low-level lapse rates and DCAPE greater than 1000 J/kg will
   favor high-based, multicell storm clusters capable of producing
   isolated severe outflow winds and marginally severe hail late this
   afternoon into early tonight.

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z