SPC AC 040539

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1239 AM CDT Tue Apr 04 2017

   Valid 041200Z - 051200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS IN PORTIONS OF
   NORTHEASTERN OKLAHOMA...SOUTHEASTERN KANSAS...AND FAR SOUTHWESTERN
   MISSOURI...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS IN PORTIONS OF
   SOUTHEASTERN MISSISSIPPI AND SOUTHWESTERN ALABAMA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
   OKLAHOMA NORTHEASTWARD INTO CENTRAL MISSOURI...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PORTIONS OF THE
   GULF COAST STATES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM MUCH OF
   OKLAHOMA NORTHEASTERN TO FAR WESTERN ILLINOIS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE GULF COAST REGION AND DEEP SOUTH...

   ...SUMMARY...
   Scattered strong to severe thunderstorms will be possible across
   parts of the south-central Plains into the Ozarks this afternoon and
   early evening, and across parts of the central Gulf Coast states
   late tonight into early Wednesday morning.

   ...Synopsis...
   A vigorous mid/upper trough and attendant powerful jet over the
   Intermountain West will migrate eastward over the central Plains in
   the afternoon and evening.  As this occurs, southwesterly mid-level
   flow will strengthen across portions of the southern Plains and
   eventually the lower- and mid-Mississippi Valley regions.  At the
   surface, a low - initially over western north Texas - will deepen
   some while migrating northeastward across central Oklahoma and into
   southwestern Missouri by the end of the period.  Late in the period,
   a warm front along the Gulf Coast will migrate inland to portions of
   central Mississippi and Alabama by the end of the period.

   ...Portions of the southern Plains and adjacent Ozarks...
   Strengthening flow aloft will commence with the approach of the
   mid-level disturbance.  Forcing for ascent associated with the
   approaching trough, convergence along the nose of a 30-40 kt
   low-level jet nearly perpendicular to a stationary surface boundary
   over Oklahoma, and steep mid-level lapse rates will all foster the
   development of scattered thunderstorms perhaps as early as late
   morning.  Elevated thunderstorms north of the surface boundary
   should foster mostly a severe hail risk.  Storms developing on the
   warm side of this boundary should have relatively high bases (owing
   to modest moisture return and low to mid-50s F dewpoints), although
   very steep low- and mid-level lapse rates should foster a hail and
   wind threat with this activity.  Activity should eventually
   consolidate into a line or linear segments that will move
   northeastward, with a continued hail/wind and isolated tornado
   threat into the overnight.  This line, although in a weakened state,
   may reach portions of western Illinois by the end of the forecast
   period.

   ...Southeastern Louisiana, southern and eastern Mississippi, much of
   Alabama, western Georgia, and the Florida Panhandle...
   Low-level warm advection in response to the Plains mid-level
   disturbance will foster northward retreat of a stationary front
   currently across the central/northeastern Gulf of Mexico.  This
   eventual warm front will migrate inland late in the period, with low
   70s dewpoints fostering moderate instability in portions of the
   region amidst a weakly capped, yet strongly sheared airmass.  Subtle
   height falls associated with the approaching mid-level disturbance,
   broad warm-sector confluence, and convergence along the warm front
   will foster the development of a few thunderstorms overnight in
   southeastern Louisiana spreading northeastward toward the end of the
   forecast period.  All modes of severe are possible with this
   activity, along with potential for a few tornadoes especially in the
   'enhanced' risk area across southeast Mississippi and southwest
   Alabama.  Farther northeast, elevated thunderstorms will foster a
   hail risk in portions of central Alabama toward 12Z.

   ..Cook/Dial.. 04/04/2017

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