May 26, 2017 1730 UTC Day 2 Convective Outlook
Updated: Fri May 26 17:36:22 UTC 2017 (20170526 1730Z Day 2 shapefile | 20170526 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170526 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MODERATE 68,210 5,915,034 St. Louis, MO...Springfield, MO...St. Charles, MO...Springdale, AR...St. Peters, MO...
ENHANCED 142,046 13,589,130 Nashville, TN...Kansas City, MO...Tulsa, OK...Lexington-Fayette, KY...Louisville, KY...
SLIGHT 233,178 30,955,711 Dallas, TX...Indianapolis, IN...Memphis, TN...Fort Worth, TX...Arlington, TX...
MARGINAL 337,274 40,889,807 Columbus, OH...Baltimore, MD...Charlotte, NC...Washington, DC...Oklahoma City, OK...
Probabilistic Graphic
20170526 1730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 2 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 132,732 9,983,105 Tulsa, OK...St. Louis, MO...Springfield, MO...Denton, TX...Broken Arrow, OK...
45 % 76,053 6,723,000 St. Louis, MO...Springfield, MO...Evansville, IN...St. Charles, MO...Springdale, AR...
30 % 134,203 12,781,163 Nashville, TN...Kansas City, MO...Tulsa, OK...Lexington-Fayette, KY...Louisville, KY...
15 % 233,178 30,955,711 Dallas, TX...Indianapolis, IN...Memphis, TN...Fort Worth, TX...Arlington, TX...
5 % 337,433 40,893,717 Columbus, OH...Baltimore, MD...Charlotte, NC...Washington, DC...Oklahoma City, OK...
   SPC AC 261736

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1236 PM CDT Fri May 26 2017

   Valid 271200Z - 281200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR THE OZARK
   PLATEAU INTO THE LOWER OHIO VALLEY...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EASTERN
   OKLAHOMA AND KANSAS EASTWARD INTO MUCH OF KENTUCKY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE
   CENTRAL-SOUTHERN GREAT PLAINS INTO THE SOUTHERN APPALACHIAN
   STATES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK...

   ...SUMMARY...
   Widespread severe gusts are likely from the Ozark Plateau into the
   lower Ohio Valley.  Large to giant hail, tornadoes, and wind damage
   are possible for parts of Oklahoma, Kansas, and eastward into
   portions of the Ohio Valley.

   ...Synopsis...
   A closed 500-mb low will meander southeast across Manitoba while a
   mid-level trough will move from WY/UT east into the central High
   Plains by Saturday evening and into the Upper Midwest/central Plains
   by early Sunday.  A belt of strong west-southwesterly mid- to
   high-level flow will extend from OK/TX eastward through the Ozarks
   and into the OH Valley/southern Appalachians.  At the surface, a low
   near the OK/KS border will develop east into the lower MO Valley
   during the afternoon with a cold front extending from eastern KS
   southwest into northern OK and arcing west into the TX Panhandle.  A
   triple point near north-central/northeast OK is forecast with a
   dryline extending south near I-35 in OK/TX during the late
   afternoon.

   ...Ozark Plateau into the lower OH Valley...
   Very rich low-level moisture will advect northward into the region
   south of a west-east frontal zone.  A very unstable to extremely
   unstable airmass will likely develop across at least the southern
   portion of this region.  Several scenarios are possible regarding
   the severe threat for this region, especially over MO.  Model
   guidance appears to be converging towards the development of a
   severe MCS moving east from MO into the lower OH Valley.  Details
   regarding timing and evolution are still somewhat uncertain at this
   time and possibilities include the following:
   1) A remnant MCV from overnight Friday storm activity may serve as
   an initiating feature for a thunderstorm cluster to grow upscale.
   2) Supercells with all severe hazards (including tornadoes)
   transitioning to a severe convective windstorm across the Ozarks.
   Given the overall environment, it appears significant severe with
   all hazards is possible.  The veering of a southwesterly LLJ into
   the OH Valley during the evening will likely aid in maintaining a
   severe threat into the evening.

   ...OK-TX dryline...
   An initial strong capping inversion will lead to extreme instability
   developing by mid afternoon to the east of the dryline over eastern
   OK into northeast TX.  Rich low-level moisture characterized by
   lowest 100-mb mean mixing ratios 17-19 g/kg beneath very steep
   700-500 mb lapse rates (8-9 degrees C/km) will result in (4500-6500
   J/kg MLCAPE per forecast soundings.  Despite generally weak forcing
   for ascent, the combination of eroding MLCINH due to strong heating
   and perhaps some contribution due to a 55-kt 500 mb speed max moving
   over OK during the late afternoon will contribute to the cap locally
   eroding and isolated thunderstorm development from northeast OK
   south into north-central TX between 21-02Z.  Strong effective shear
   (50 kt) and extreme buoyancy will rapidly favor supercell
   development early in the convective life cycle.  Giant hail (3.0-4.5
   inches in diameter) is possible with any established supercell. 
   NAM/GFS forecast soundings show gradual veering and strengthening of
   the wind profile in the lowest 2-3 km --- yielding 100-250 m2/s2 0-1
   km SRH from south to north across this region.  The possibility
   exists for significant tornadoes with supercells, especially across
   the northeastern quarter of OK into southeastern KS and into MO.  A
   cluster of storms will probably evolve during the evening with
   hail/wind becoming the predominant risk late Saturday night as
   activity moves east into AR.  

   ...Southern Appalachians...
   Models show moderate buoyancy developing during the day with
   deep-layer shear supportive of organized thunderstorms.  Hail/wind
   will be the primary hazards with weakening of the storms and a
   corresponding decrease in severe risk associated with cooling during
   of the boundary layer during the evening.

   ..Smith.. 05/26/2017

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