SPC AC 101950

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0250 PM CDT Sun Oct 10 2021

   Valid 102000Z - 111200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THROUGH THIS
   EVENING ACROSS PARTS OF OKLAHOMA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH THIS
   EVENING OVER NORTHEAST MINNESOTA...

   ...SUMMARY...
   Tornadoes, widespread damaging wind gusts, and very large hail are
   forecast this afternoon and evening for portions of Oklahoma and
   north Texas.

   ...MN...

   Only minor changes have been made to the Slight risk area across
   northern MN with the 20z update. Slight risk probabilities have been
   nudged southward a small amount based on ongoing convection this
   afternoon. Hail and a couple of tornadoes will be possible through
   early evening with WW 516 in effect until 02z.

   ...Southern Plains...

   The previous outlook remains on track and no changes have been made
   with the 20z update. Initial supercells are expected to initiate
   over southwest OK near the surface low by around 22z and track
   east/northeast toward central OK (including the OKC metro area) by
   00z. Very large hail, damaging gusts and potentially significant
   (EF2+) tornadoes will be possible. As the surface cold front starts
   to surge south/southeast this evening, upward development into a
   fast-moving QLCS capable of widespread damaging wind gusts,
   tornadoes and hail will sweep across central/eastern OK (including
   the Tulsa metro area by around 02-03z). For more details on the
   short term severe risk reference MCD 1820.

   Scattered storms will also develop southward along the surface
   dryline/cold front across northern/central TX by 23-00z (and the
   Dallas-Fort Worth metroplex by around 01-02z). Initial supercells
   may evolve into a broken line with eastward extent through the
   evening, but large hail, damaging gusts and a few tornadoes all will
   be possible with this activity.

   ..Leitman.. 10/10/2021

   .PREV DISCUSSION... /ISSUED 1116 AM CDT Sun Oct 10 2021/

   ...OK...
   An intense and fast-moving shortwave trough over western NM will
   pivot into the southern Plains this afternoon.  Ahead of this
   trough, a surface low is forecast to rapidly deepen over western
   North TX and track northeastward into central OK this evening. 
   Strong and strengthening low-level wind fields in the warm sector of
   the low will transport Gulf moisture northward, with dewpoints in
   the mid-upper 60s expected across the region.  A combination of
   ample sunshine and slowing cooling mid-level temperatures will yield
   MLCAPE values around 2000 J/kg by peak heating, with a slowly
   weakening cap.

   Current indications are that storms will begin to rapidly intensify
   after 21z near the surface low in southwest OK.  Some of this
   activity will be north of the associated cold front, with a primary
   risk of large hail.  However, morning CAM solutions continue to
   suggest that discrete supercell development is possible near the low
   and along the trailing dryline.  These storms will be in an
   environment of rapidly strengthening low/mid level wind fields and
   vertical shear, steep lapse rates, and intense large-scale forcing. 
   Forecast soundings/hodographs in the warm sector would favor the
   potential for strong tornadoes, very large hail, and significant
   damaging winds as storms track across central OK - mainly after
   dark.  

   Storms will become more numerous as they race northeastward into
   eastern OK during the evening.  A few discrete supercells may
   persist, along with an increasing threat of QLCS-associated wind
   damage and tornadoes.  It appears likely the storms will begin to
   weaken as they move into parts of western MO/AR around midnight.

   ...TX...
   Farther south, model consensus shows scattered thunderstorms
   developing this evening along the dryline across northern and
   central TX - especially as the cold front overtakes the dryline. 
   Strong forcing aloft and strengthening wind fields will pose a risk
   of a scattered supercells along this corridor, capable of a few
   tornadoes, large hail, and damaging winds.

   ...MN...
   An upper low over MN will move slowly eastward today, helping to
   initiate scattered afternoon thunderstorms over the Arrowhead
   region.  Extensive low clouds in this area will limit daytime
   heating and destabilization.  However, a few of the low-topped
   storms may be capable of hail or brief tornadoes for a few hours
   this afternoon.  Storms should track northward and into Canada
   around dusk, ending the threat.

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