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    Day 2 Outlook >
Aug 18, 2017 2000 UTC Day 1 Convective Outlook
Updated: Fri Aug 18 19:24:14 UTC 2017 (Print Version | 20170818 2000Z Day 1 shapefile | 20170818 2000Z Day 1 KML)
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 Forecast Discussion
   SPC AC 181924

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0224 PM CDT Fri Aug 18 2017

   Valid 182000Z - 191200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MID
   ATLANTIC INTO SOUTHERN NEW YORK...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHWEST
   MINNESOTA AND VICINITY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTHWEST MISSOURI...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
   TO MIDDLE MISSOURI VALLEY INTO NORTHERN OKLAHOMA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
   THE MID ATLANTIC INTO SOUTHERN NEW ENGLAND...

   ...SUMMARY...
   Scattered strong to localized severe gusts capable of wind damage
   are forecast from the Chesapeake Bay vicinity northward into
   southern New York.  Isolated severe thunderstorms are possible
   across portions southwestern Minnesota and northern Missouri.

   No changes were necessary to the existing outlook.

   ..Jewell.. 08/18/2017

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Fri Aug 18 2017/

   ...Mid-Atlantic region...
   Daytime heating of a very moist boundary layer in place east of the
   mountains is ongoing, within a relatively cloud-free zone from
   southeast Pennsylvania south-southwestward east of the Appalachian
   crest.  As moderate CAPE develops through early to mid afternoon, an
   increase in storms -- particularly within a weak zone of convergence
   observed in lee of the mountains -- is expected.  Strongest flow
   aloft will remain largely north of the area of greatest anticipated
   destabilization, but amply strong west-southwest flow extending
   southward across the mid-Atlantic region will likely support a few
   stronger storms/bands of storms.  As such, 15% wind probability/SLGT
   risk remains evident across this region.  Convection will move
   eastward with time, weakening into the early evening hours as storms
   approach/move off the coast.

   ...Southwest Minnesota...
   A compact center of circulation remains evident near the southeast
   North Dakota/northeast South Dakota border, moving slowly
   southeastward with time.  As clouds/lingering precipitation continue
   to move east across Minnesota, diurnal heating will permit ample
   destabilization -- supportive of convective redevelopment near/ahead
   of the center of circulation.  With amply strong deep-layer
   northwesterly flow aloft, an organized, southeastward-moving cluster
   of storms may evolve, with associated risk for locally damaging
   winds and hail.  Convection should weaken into the evening as it
   shifts south-southeast out of Minnesota and across Iowa with time.

   ...Parts of northern Missouri...
   As weak large-scale ascent spreads southeast in conjunction with
   mid-level short-wave troughing over the north-central states, a weak
   surface low and convergence zone now over the western IA vicinity
   will likewise drift southeast.  Agreement amongst some CAM members,
   and morning NAM and GFS output, suggest that storms will develop
   over the northern Missouri vicinity this afternoon/evening near the
   low, as destabilization peaks.  With amply strong northwest flow
   aloft, storms may organize locally, possibly growing upscale into an
   organized band with time.  Risk for hail and locally damaging winds
   may evolve with any stronger convection, warranting continuation of
   SLGT risk for this afternoon and evening.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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Page last modified: August 18, 2017
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