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    Day 2 Outlook >
Apr 27, 2017 0600 UTC Day 1 Convective Outlook
Updated: Thu Apr 27 04:49:06 UTC 2017 (Print Version | 20170427 1200Z Day 1 shapefile | 20170427 1200Z Day 1 KML)
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 Forecast Discussion
   SPC AC 270449

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1149 PM CDT Wed Apr 26 2017

   Valid 271200Z - 281200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
   THE GREAT LAKES REGION SOUTHWARD TO THE SOUTHEAST STATES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF SOUTHEAST CO...WESTERN/SOUTHERN KS...THE TX/OK
   PANHANDLES...NORTHERN OK...

   ...SUMMARY...
   Isolated severe wind gusts may accompany thunderstorms from portions
   of the Great Lakes region to the Southeast States today into this
   evening, and across portions of the central and southern Great
   Plains late this afternoon into this evening.

   ...Synopsis...
   Deep surface low pressure is forecast to advance from the vicinity
   of Lake Michigan northward into Ontario, associated with a
   northward-advancing shortwave trough embedded within the eastern rim
   of broadly cyclonic flow covering the Central and Western States. A
   cold front will arc south from the low to the north-central Gulf
   Coast vicinity and westward. The South-Central States portion of the
   front is forecast to weaken and develop northward in response to
   surface lee cyclogenesis over the central High Plains -- enhanced by
   the emergence of a midlevel speed maximum from the central/southern
   Rockies vicinity.

   ...Portions of the Great Lakes region southward to the Southeast
   States...
   Comparatively stronger deep ascent accompanying the
   northward-advancing shortwave trough is forecast to become
   increasingly displaced to the north of richer moisture within the
   low-level cyclone's warm sector. This will tend to marginalize the
   severe potential through the period. Nevertheless, storm coverage
   and intensity are forecast to gradually increase through the diurnal
   heating cycle along and ahead of the front, with an extensive
   corridor of eastward- and northeastward-moving clusters of storms
   across the Marginal Risk area. Isolated damaging wind gusts should
   be the primary hazard with this activity.

   The strongest pre-frontal buoyancy related to the richest low-level
   moisture characterized by middle/upper 60s dewpoints will be
   confined to portions of central SC into GA and vicinity. While
   effective shear around 30-40 kt and modest low-level directional
   shear may support a few rotating updrafts, weakening low-level
   ascent will tend to limit updraft sustainability and keep any severe
   risk isolated.

   Farther north, diurnal gains in buoyancy will be muted by cloud
   coverage and more scant moisture return northward to the Great Lakes
   region and vicinity. However, sufficient low/midlevel flow could
   encourage momentum transport capable of supporting locally damaging
   wind gusts.

   Storms across the Marginal Risk area will weaken during the evening
   as they spread across an area from western NY southward to the SC
   piedmont.

   ...Portions of southeast CO, western/southern KS, the TX/OK
   Panhandles, northern OK...
   Strengthening deep ascent associated with the aforementioned speed
   maximum, including isentropic ascent related to lee cyclogenesis,
   will support the development of convective clusters in the
   steep-lapse-rate environment across the High Plains by late
   afternoon. Convection will subsequently spread eastward along a zone
   of frontogenesis through the evening hours. A dearth of moisture
   return will greatly stunt buoyancy. However, long/looping hodographs
   amid sufficient buoyancy and the steep lapse rates may support a few
   bowing convective segments capable of isolated severe wind gusts.

   ..Cohen/Leitman.. 04/27/2017

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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Page last modified: April 27, 2017
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