SPC AC 211728

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1228 PM CDT Wed Aug 21 2019

   Valid 221200Z - 231200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   NORTHERN AND CENTRAL HIGH PLAINS REGION...AND FROM NEW ENGLAND
   SOUTHWESTWARD TO THE CENTRAL APPALACHIANS...AND THEN WESTWARD TO
   OKLAHOMA...

   ...SUMMARY...
   Isolated severe wind gusts are possible Thursday from Oklahoma
   eastward across the Ohio Valley and into parts of New England. 
   Meanwhile, hail or wind, occasionally reaching severe levels, will
   also be possible over the central and northern High Plains area.

   ...Synopsis...
   Weak flow aloft is progged across the southern half of the U.S.
   Thursday, while a part of troughs will cross Canada and the adjacent
   northern U.S. through the period.  The more western of these
   features is expected to cross the northern Intermountain region, as
   an accompanying surface cold front crosses Montana/Wyoming during
   the afternoon and evening.  Farther east, a trough crossing the
   Great Lakes region will also be accompanying by a cold front, that
   is forecast to shift eastward across the Northeast, while sagging
   more slowly southward across the Ohio and mid Mississippi Valleys
   and into Oklahoma.  Both of the troughs, and the associated surface
   systems, will contribute to convective activity, and accompanying,
   low-probability severe potential, through the period.

   ...Parts of New England southwest across the Ohio Valley area to
   Oklahoma...
   Modest destabilization is forecast near and ahead of a surface cold
   front progged to stretch from New England southwestward across the
   Ohio Valley to Oklahoma during the afternoon, as the parent upper
   trough slowly advances across eastern Canada and the Great Lakes
   region.  Scattered to isolated afternoon storm development is
   expected near the boundary, and southward across the warm sector.

   While any warm-sector storm could produce briefly/locally gusty
   winds, weak flow will substantially limit storm
   organization/longevity.  Farther north however, nearer the front, an
   enhanced belt of cyclonic westerlies surrounding the upper trough
   will be sufficient to support longer-lived storms, and possibly a
   few quick-moving clusters of cells.  As such, local risk for
   damaging wind gusts appears sufficient across a broad region within
   the  the frontal zone to warrant continuation of 5% wind/MRGL risk. 
   The risk are is being expanded northeastward across the mid Atlantic
   region and into parts of New England, where lesser CAPE, but
   stronger flow aloft, is expected.

   ...Portions of the northern and central high Plains...
   Afternoon heating will result in moderate destabilization across the
   high Plains near the combination lee trough/remnant cold front, with
   lesser destabilization to occur westward into central Montana ahead
   of the next/advancing cold front.  Both of these fronts/troughs
   should focus afternoon/evening convective activity, with some
   clustering of convection possible over the high Plains that may
   locally progress eastward into lower-elevation areas.

   While mid-level westerly flow will remain modest across much of the
   area -- particularly the central high Plains, low-level
   southeasterlies east of the lee trough/remnant front will help to
   enhance the available shear, and thus a few stronger storms/storm
   clusters -- capable of locally gusty winds and/or hail -- are
   expected to evolve.  Risk will primarily exist during the late
   afternoon and evening hours, diminishing overnight as the boundary
   layer stabilizes.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   2%     - Marginal
   Wind:      5%     - Marginal
   Hail:      5%     - Marginal

   ..Goss.. 08/21/2019

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