Aug 25, 2017 0600 UTC Day 2 Convective Outlook
Updated: Fri Aug 25 06:08:29 UTC 2017 (20170825 0600Z Day 2 shapefile | 20170825 0600Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170825 0600 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 14,137 4,478,093 Houston, TX...Pasadena, TX...Beaumont, TX...Sugar Land, TX...Missouri City, TX...
MARGINAL 119,487 4,308,558 Omaha, NE...Lincoln, NE...Des Moines, IA...Lake Charles, LA...Rapid City, SD...
Probabilistic Graphic
20170825 0600 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 2 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 133,802 8,906,353 Houston, TX...Omaha, NE...Lincoln, NE...Des Moines, IA...Pasadena, TX...
   SPC AC 250608

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0108 AM CDT Fri Aug 25 2017

   Valid 261200Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ALONG AND INLAND
   OF THE MIDDLE TO UPPER TX COAST INTO SOUTHWEST LA...PRIMARILY FOR A
   TORNADO THREAT...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK FROM THE TX COAST TO SOUTHWEST LA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   WESTERN AND CENTRAL SD THROUGH NE TO WESTERN IA...

   ...SUMMARY...
   A tornado threat will exist near and to the north to northeast of
   the inland track of Hurricane Harvey on Saturday, primarily along
   and inland of the middle to upper Texas coast.  Meanwhile, a couple
   of severe storms may develop near and southeast of the Black Hills
   late Saturday afternoon, before spreading into parts of west-central
   Nebraska Saturday evening.  Isolated severe storms could also
   develop into eastern Nebraska to western Iowa Saturday afternoon and
   evening.

   ...Synopsis...
   Latest National Hurricane Center guidance as of 25/06Z indicated
   Hurricane Harvey will be near the TX coast between CRP and VCT at
   26/12Z, with some continued inland movement toward the northwest. 
   Meanwhile across the rest of the contiguous U.S., 500-mb heights are
   expected to rise across the Great Basin, with a ridge building from
   the Pacific Northwest into the southern portions of the western
   Canadian Provinces.  Northwesterly winds are expected to strengthen
   across the northern Plains into NE within the northeast periphery of
   the western ridge and a shortwave trough tracking into the Upper
   Midwest.  At the surface, a weakening area of low pressure will
   track east across southern MN with a trailing cold front advancing
   southeast and south across IA and NE.

   ...TX Coastal Plain to southwest LA...
   Given the presence of Hurricane Harvey moving inland some across the
   northern portion of the lower TX to middle TX coast, enlarged
   clockwise hodograph curvature and some instability suggest a
   potential tornado threat will exist this forecast period.

   ...Southern MN/IA/eastern NE...
   A cluster of storms, possibly an MCS, should be ongoing at 12Z
   Saturday across parts of southern MN and northwest to northern IA. 
   This activity will be associated with a weak mid-level impulse
   tracking across MN and northern IA late day 1 into early day 2. 
   This impulse is expected to move into WI and the Upper Great Lakes
   Saturday, while models suggest warming 500-mb temperatures in its
   wake.  Although convection may continue to form along and ahead of
   the ongoing MCS into Saturday afternoon, weak instability/shear
   suggest the severe threat should be too low to introduce severe
   probabilities across northern IA into MN.

   Greater destabilization will be possible across parts of western IA
   and eastern NE near the cold front, as greater potential will exist
   for surface heating to the south of the cloudiness and early day
   convection/thunderstorms farther north.  Despite this factor, weak
   effective bulk shear may limit the overall severe threat.

   ...Parts of western and central SD and NE...
   Despite weak low-level winds, strengthening northwesterly 500-mb
   winds of 30-35+ kt and vertically veering wind profiles suggest the
   potential for organized convective development, including an
   isolated supercell or two, and perhaps the evolution of a small
   convective system.  Late Saturday afternoon CAPE should be modest
   with MLCAPE up to 1000 J/kg.  These factors and steep mid-level
   lapse rates suggest some severe potential.  Given weak forcing
   aloft, orographic forcing near the Black Hills may support
   initiation of activity Saturday afternoon, with some potential for
   upscale growth into western NE within an area of increasing
   low-level warm-air advection. Isolated hail and strong/damaging wind
   gusts will be the primary threats.

   ..Peters.. 08/25/2017

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