SPC AC 020825

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0225 AM CST Fri Mar 02 2018

   Valid 041200Z - 051200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY AFTERNOON
   AND EVENING ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS...

   ...SUMMARY...
   Widely scattered strong storms may impact portions of the central
   and southern Plains Sunday afternoon and evening, accompanied by at
   least some risk for severe weather.

   ...Discussion...
   Blocking appears likely to remain prominent within the large-scale
   pattern across parts of eastern Canada into the western Atlantic
   during this period.  However, models do indicate that upper
   troughing, including one vigorous short wave, will emerge from the
   intermountain west and suppress upper ridging east of the Rockies,
   as it progresses across the Rockies into the northern and central
   Plains Sunday through Sunday night.  Guidance continues to indicate
   that the short wave impulse will provide support for fairly
   significant surface cyclogenesis from the central High Plains
   through the middle Missouri Valley.  The short wave may be preceded
   on its southern through southeastern periphery (across Oklahoma and
   northern Texas into the lower Mississippi Valley) by another
   substantive impulse of subtropical eastern Pacific origins.

   A modest return flow of moisture off a modifying boundary layer over
   the western Gulf of Mexico probably will already be underway by
   early Sunday.  However, there may be little further appreciable
   increase in moisture quality (mid 60s across central/eastern Texas)
   through the period, hampered by low-level drying in the wake of the
   broad, deep cyclone over the western Atlantic.  And northward
   moisture return within the warm sector into the central Plains may
   be confined to a relatively narrow wedge.  But this is expected to
   take place in the presence of at least modestly steep lower/mid
   tropospheric lapse rates, beneath a plume of elevated mixed layer
   air emerging from the Mexican Plateau, prior to the onset of
   mid-level cooling associated with the approaching mid-latitude
   trough.  It does appear that the stronger mid-level cooling may
   advance eastward to the north of the better low-level moisture
   across Texas.

   ...Central and southern Plains...
   Convective potential for Sunday through Sunday night remains
   somewhat unclear due to a number of uncertainties (some already
   alluded to).  The environment appears potentially supportive of a
   window of opportunity for supercell development, but any potential
   for boundary-layer based supercells may be confined to a rather
   narrow corridor across parts of northwest Texas, the eastern Texas
   Panhandle and adjacent portions of western Oklahoma through west
   central Kansas.  This would be along the dry line during the late
   afternoon and early evening.  However, most current model output is
   suggestive that any thunderstorm development across this region will
   be isolated at best.  

   There currently appears a stronger signal that scattered
   thunderstorm development may initiate east of the dry line, perhaps
   across parts of northwest Texas into western Oklahoma by midday,
   before spreading eastward toward the Ozark Plateau, and perhaps
   northward toward the mid/lower Missouri Valley ahead of the
   mid-latitude impulse.  Much of this seems likely to be elevated
   above a cooler/stable boundary layer, but the lapse rates and
   favorable shear may support at least a marginal severe hail risk
   across the lower Plains before this threat diminishes to the east.

   In the wake of the subtropical perturbation, and ahead of the
   southern edge of the mid-latitude trough axis, it also does not seem
   out of the question that mid-level inhibition could weaken
   sufficiently for isolated boundary layer supercell development 
   across parts of central/northeast Texas before the boundary layer
   stabilizes late Sunday evening.

   ..Kerr.. 03/02/2018

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