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Aug 19, 2017 0600 UTC Day 2 Convective Outlook
Updated: Sat Aug 19 05:02:21 UTC 2017 (Print Version | 20170819 0600Z Day 2 shapefile | 20170819 0600Z Day 2 KML)
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 Forecast Discussion

   SPC AC 190502

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1202 AM CDT Sat Aug 19 2017

   Valid 201200Z - 211200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY INTO
   SUNDAY NIGHT ACROSS MUCH OF THE MID MISSOURI RIVER VALLEY...

   ...SUMMARY...
   Strong thunderstorms may impact portions of the mid Missouri Valley
   Sunday into Sunday night, accompanied by at least some risk for
   severe weather.

   ...Synopsis...
   Models suggest that the stronger mid-latitude westerlies will
   retreat to the north of the Canadian/U.S. border during this period.
   This regime is expected to become largely zonal, though ridging may
   begin to build across the British Columbia coast and Canadian
   Rockies, downstream of an upper trough and embedded closed low
   digging to the southeast of the eastern Aleutians.  It still appears
   that one fairly significant short wave impulse will pivot northeast
   of Manitoba, toward southern Hudson/James Bays, early in the period.
   An associated cold front may advance as far south as the upper Great
   Lakes and Upper Midwest, into the South Dakota/Nebraska border area,
   before stalling.

   In lower latitudes, western Atlantic subtropical ridging appears
   likely to continue building westward across the Southeast, and
   expanding westward/northward through the southern Plains, middle
   Mississippi and Ohio Valleys.  At the same time, broad troughing
   with a number of embedded perturbations may continue to evolve, from
   west of the California coast into the southern Great Basin and
   Rockies.

   ...Much of the middle Missouri Valley...
   Considerable spread has been evident among the various models
   concerning the pertinent features that will impact convective
   development during this period.  This still includes the positioning
   of the zone of potentially strong differential surface heating and
   related plume of warm and potentially capping elevated mixed layer
   air, on the southern fringe of the westerlies, and any possible
   subtle mid/high-level perturbations traversing the region. 
   Additionally, portions of the pre-frontal environment across the mid
   Missouri Valley region may be in the process of recovering from
   impacts of convection developing late Saturday/Saturday night.  And
   the strength/position of the nocturnal low-level jet is becoming
   more unclear.

   Latest model output does continue to suggest the development of
   moderate to large CAPE across at least portions of the region, with
   continued low-level moistening beneath steep mid-level lapse rates. 
   In the presence of modest vertical shear, with a large contribution
   from veering of winds with height, the environment may still become
   conducive to severe storm potential Sunday/Sunday night.  However,
   this threat appears increasingly conditional, probably mostly on
   where stronger lower/mid tropospheric warm advection provides a
   focus for storm formation.  Uncertainties appear too large for this
   outlook to maintain earlier slight risk probabilities for this time
   period.

   ..Kerr.. 08/19/2017

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z

        
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Page last modified: August 19, 2017
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