SPC AC 210049

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0749 PM CDT Fri Sep 20 2019

   Valid 210100Z - 211200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE NORTHERN PLAINS AND CENTRAL HIGH PLAINS...

   ...SUMMARY...
   Scattered severe storms capable of producing wind damage, isolated
   large hail and a couple tornadoes are possible this evening across
   parts of the northern Plains, with more isolated severe storms
   possible in parts of the southern High Plains.

   ...Northern Plains/Central High Plains...
   The latest water-vapor imagery shows an upper-level low over the
   northern Rockies with southwest mid-level flow over the northern
   Plains. A couple perturbations in the flow appear to be moving
   across the northern Plains. The first is located in central North
   Dakota where numerous thunderstorms are ongoing. The second is
   located in western Nebraska where scattered thunderstorms are
   ongoing. At the surface, a cold front is located from far
   northeastern Wyoming northeastward into central North Dakota. To the
   east of the front, a moderately to strongly unstable airmass is
   present. This is coincident with moderate deep-layer shear which
   will support a severe threat this evening. The mass of convection
   over east-central North Dakota is expected to organize into a nearly
   continuous line and move slowly east-northeastward. This line will
   likely be accompanied with wind damage and isolated large hail. More
   discrete cells should continue to develop to the east of this line
   across eastern North Dakota and northwestern Minnesota. The stronger
   cells within this cluster may obtain supercell characteristics and
   have isolated large hail, wind damage and a tornado or two...see MCD
   1991.

   Further southwest across northwest Nebraska and central South
   Dakota, a low-level jet will strengthen this evening. In response,
   thunderstorm coverage should gradually increase as storms develop
   across southern and central South Dakota over the next few hours.
   The strengthening low-level jet will create long hodographs
   favorable for rotating storms. A few that become supercells will
   have potential to produce large hail and an isolated tornado threat.
   As storm coverage becomes more numerous late this evening, wind
   damage and hail should become the predominant severe threat.

   ...Southern Plains...
   The latest water-vapor imagery shows southwest mid-level flow over
   the southern Plains with a minor shortwave trough located over
   southern Oklahoma. Scattered thunderstorms are ongoing near the
   shortwave trough. Near the trough, the airmass is moderately
   unstable with 0-6 km shear in the 30 to 35 kt range. This should be
   enough for a marginal severe threat for another hour or two as a
   bowing line segment moves eastward across northwest Texas and far
   southern Oklahoma. Isolated damaging wind gusts and hail will be
   possible.

   ..Broyles.. 09/21/2019

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