SPC AC 220825

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0225 AM CST Sun Nov 22 2020

   Valid 241200Z - 251200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN/CENTRAL PLAINS INTO THE OZARKS...MID-SOUTH...AND LOWER
   MISSISSIPPI VALLEY...

   ...SUMMARY...
   Isolated strong to severe thunderstorms appear possible Tuesday into
   Tuesday night across portions of the southern/central Plains,
   Ozarks, Mid-South, and lower Mississippi Valley.

   ...Southern Plains into the Ozarks and Lower Mississippi Valley...
   An upper trough/low initially centered over the southern/central
   Rockies should eject eastward across the southern/central Plains on
   Tuesday, eventually reaching the lower/mid MS Valley by the end of
   the period. Enhanced (50-60+ kt) mid-level southwesterly winds will
   likely overspread much of the developing warm sector across the
   southern/central Plains by Tuesday evening. A surface low over the
   vicinity of western KS/NE Tuesday morning is forecast to develop
   eastward towards the mid MS Valley through the period. Pronounced
   low-level warm/moist advection will likely be ongoing across the
   southern/central Plains Tuesday morning, with a 40-50+ kt
   south-southwesterly low-level jet present over this region. As this
   low-level jet shifts eastward across the Ozarks and lower/mid MS
   Valley through the day, partially modified Gulf moisture will
   likewise return northward.

   Elevated convection may be ongoing Tuesday morning across the
   southern/central High Plains associated with low-level warm
   advection. As mid-level temperatures cool with the approach of the
   upper trough and low-level moisture continues streaming northward
   across the southern Plains, at least weak instability should develop
   by late Tuesday afternoon along and east of a surface cold front and
   dryline. Somewhat steepened mid-level lapse rates and strong
   deep-layer shear may support isolated, marginally severe hail with
   any initially discrete storms across OK and perhaps south-central
   KS. By Tuesday evening, any storms that do form will likely grow
   upscale into a line along the advancing cold front. Given the
   predominately linear mode and enhanced low-level wind field,
   isolated strong to damaging winds should become the main threat
   across the Ozarks, Mid-South, and lower MS Valley region Tuesday
   night into early Wednesday morning.

   There is uncertainty regarding the quality and northward extent of
   greater low-level moisture return, with the 00Z GFS/ECMWF suggesting
   mid to perhaps upper 50s surface dewpoints may reach as far north as
   south-central/southeastern KS into southern MO and the Mid-South.
   The 00Z NAM shows less low-level moisture return across these areas.
   Regardless, there will probably be enough low-level moisture and
   related weak instability to support surface-based storms and
   isolated strong/gusty wind potential with a low-topped convective
   line. Farther south into parts of central/eastern OK, AR, northeast
   TX, northern LA, and MS, the presence of somewhat higher dewpoints
   along with enhanced low-level shear may support a slightly greater
   tornado threat compared to locations farther north. Model
   differences regarding the degree of low-level moisture return and
   weak forecast instability suggest there is too much uncertainty to
   include more than a broad Marginal risk area at this time.

   ..Gleason.. 11/22/2020

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