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Sep 25, 2017 1730 UTC Day 2 Convective Outlook
Updated: Mon Sep 25 16:53:41 UTC 2017 (Print Version | 20170925 1730Z Day 2 shapefile | 20170925 1730Z Day 2 KML)
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 Forecast Discussion

   SPC AC 251653

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1153 AM CDT Mon Sep 25 2017

   Valid 261200Z - 271200Z


   The risk of severe thunderstorms appears negligible across the U.S.
   Tuesday through Tuesday night.

   The southern branch of split westerlies emanating from the
   mid-latitude Pacific remains amplified, but a significant
   perturbation appears likely to emerge from embedded large-scale
   troughing over the western U.S., and accelerate
   northeastward/eastward across the northern Plains through the upper
   Great Lakes region during this period.  At the same time, it appears
   that a digging upstream perturbation will contribute to the
   development of another closed low within remnant upper troughing
   near/east of the lower Colorado Valley.  Downstream of this latter
   feature, a sharpening ridge is forecast to build from the lower Rio
   Grande Valley through the Tennessee/Ohio Valleys, while Maria turns
   northward to the east of the southern Mid Atlantic coast.  A weak
   mid/upper low now digging into the northeastern Gulf of Mexico
   appears likely to linger through this period and beyond.

   Models do indicate that the perturbation emerging from the
   intermountain region may provide support for cyclogenesis along a
   front now quasi-stationary across the upper Great Lakes/Upper
   Midwest region.  However, the more significant deepening and
   strengthening of lower/mid tropospheric wind fields and shear are
   expected northeast of the Great Lakes region, into the vicinity of
   James Bay.  With the mid-level cold core of the upper impulse
   lagging to the cool side of the surface frontal zone, and weak
   mid-level lapse rates limiting destabilization within the warm
   sector, the risk for severe storms still appears negligible at this

   Across the Southwest, a rather dry environment seems likely to
   initially suppress/delay convective development, but forcing for
   ascent downstream of the evolving closed low, coupled with moisture
   advection, may eventually contribute to scattered thunderstorm
   development across parts of the southern Rockies into the Colorado
   Plateau.  It appears that this is most probable after dark, with
   generally negligible risk for severe weather.

   ..Kerr.. 09/25/2017



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