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    Day 2 Outlook >
Nov 18, 2017 0600 UTC Day 1 Convective Outlook
Updated: Sat Nov 18 05:48:26 UTC 2017 (Print Version | 20171118 1200Z Day 1 shapefile | 20171118 1200Z Day 1 KML)
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 Forecast Discussion
   SPC AC 180548

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1148 PM CST Fri Nov 17 2017

   Valid 181200Z - 191200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER
   OHIO VALLEY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   GREATER OHIO VALLEY...

   ...SUMMARY...
   Thunderstorms capable of severe wind gusts, marginal hail, or a
   brief tornado will be possible Saturday mainly over the Ohio Valley
   region.

   ...Synopsis...

   A vigorous mid-level trough will quickly move east from the Plains
   toward the East Coast on Saturday. As this occurs, a surface cyclone
   near St. Louis will deepen and race to the northeast, reaching
   upstate New York by Sunday morning. Strong mid-level winds (nearing
   100 knots at 500 millibars) will overspread much of the Ohio Valley
   as a surface cold front pushes southeast.

   ...Lower Ohio Valley...

   Strong forcing for ascent along the southeastward-advancing cold
   front should allow for thunderstorms to develop in the 18-21Z time
   frame. Despite widespread cloud cover, most-unstable CAPE values
   should still increase to between 500-1000 J/kg given the degree of
   theta-e advection associated with the 50-60 knot low-level jet. The
   modest buoyancy and lower-tropospheric flow largely parallel to the
   front should result in thunderstorms organizing into one or more
   small, bowing segments. Damaging wind gusts will be possible with
   the strongest clusters/segments. Long hodographs with small loops in
   the lowest three kilometers suggest that a brief tornado cannot be
   ruled out within the larger thunderstorm clusters/segments. With
   time and eastward extent, thunderstorms should outrun the greatest
   buoyancy, diminishing the overall severe threat.

   ...Northeast Missouri eastward into Ohio...

   Strong, moist isentropic ascent on the nose of a 40-60 knot
   low-level jet should allow for elevated thunderstorms to occur along
   and north of the track of the surface low/warm front. Here,
   most-unstable CAPE values up to 1000 J/kg and mid-level-lapse rates
   between 7 and 8 C/km will support a marginal hail risk.

   ..Marsh.. 11/18/2017

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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Page last modified: November 18, 2017
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