Apr 26, 2017 0600 UTC Day 1 Convective Outlook
Updated: Wed Apr 26 05:48:03 UTC 2017 (20170426 1200Z Day 1 shapefile | 20170426 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170426 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MODERATE 22,659 1,151,202 Shreveport, LA...Bossier City, LA...Monroe, LA...Greenville, MS...Marshall, TX...
ENHANCED 78,468 5,281,555 Memphis, TN...Little Rock, AR...Jackson, MS...Tyler, TX...Longview, TX...
SLIGHT 94,747 5,371,945 Springfield, MO...Fort Smith, AR...Fayetteville, AR...Jackson, TN...Springdale, AR...
MARGINAL 153,345 25,325,189 Chicago, IL...Dallas, TX...Tulsa, OK...St. Louis, MO...Plano, TX...
Probabilistic Tornado Graphic
20170426 1200 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 30,439 1,607,873 Shreveport, LA...Bossier City, LA...Pine Bluff, AR...Monroe, LA...Greenville, MS...
15 % 21,905 1,120,820 Shreveport, LA...Bossier City, LA...Monroe, LA...Marshall, TX...Ruston, LA...
10 % 27,814 1,828,614 Little Rock, AR...Tyler, TX...Longview, TX...North Little Rock, AR...Pine Bluff, AR...
5 % 58,438 2,879,234 Jackson, MS...Conway, AR...Alexandria, LA...Lufkin, TX...West Memphis, AR...
2 % 92,651 6,773,528 Memphis, TN...Baton Rouge, LA...Lafayette, LA...Beaumont, TX...Fort Smith, AR...
Probabilistic Damaging Wind Graphic
20170426 1200 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
30 % 100,134 6,251,031 Memphis, TN...Shreveport, LA...Little Rock, AR...Tyler, TX...Longview, TX...
15 % 93,459 5,360,129 Jackson, MS...Springfield, MO...Fort Smith, AR...Fayetteville, AR...Jackson, TN...
5 % 151,391 23,986,753 Chicago, IL...Dallas, TX...St. Louis, MO...Plano, TX...Baton Rouge, LA...
Probabilistic Large Hail Graphic
20170426 1200 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SIG SEVERE 34,805 1,906,539 Shreveport, LA...Longview, TX...Bossier City, LA...Pine Bluff, AR...Monroe, LA...
30 % 22,956 1,191,282 Shreveport, LA...Bossier City, LA...Pine Bluff, AR...Monroe, LA...Greenville, MS...
15 % 144,961 8,506,767 Memphis, TN...Little Rock, AR...Jackson, MS...Tyler, TX...Fort Smith, AR...
5 % 132,788 15,836,711 Dallas, TX...St. Louis, MO...Plano, TX...Baton Rouge, LA...Garland, TX...
   SPC AC 260548

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1248 AM CDT Wed Apr 26 2017

   Valid 261200Z - 271200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS THE
   ARKLATEX REGION...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
   TEXAS TO EXTREME SOUTHERN MISSOURI...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN
   LOUISIANA TO SOUTHEAST MISSOURI...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE UPPER
   TEXAS COAST TO NORTHWEST INDIANA...

   ...SUMMARY...
   Severe thunderstorms are expected across the Lower Mississippi
   Valley Wednesday.  Tornadoes, large hail, and damaging winds should
   focus from northeast Texas across southern Arkansas and northern
   Louisiana primarily during the afternoon hours.  Isolated severe
   thunderstorms may extend as far north as Illinois and into the
   central Gulf States during the overnight hours.

   ...Lower MS Valley...

   Early-morning water vapor/radar imagery depict a well defined upper
   circulation over northeast NM shifting east-southeast in line with
   late-evening model guidance.  High-level flow is increasing across
   the southern Rockies and 500mb speeds on the order of 75kt will
   translate into central TX later today.  This feature will induce
   significant mid-level height falls across the lower MS Valley and
   encourage strengthening LLJ over LA/AR by 18z.

   26/00z observed soundings across TX depict very steep mid-level
   lapse rates, on the order of 8.5-9 c/km, and this lapse-rate plume
   should spread across the Arklatex region prior to convective
   development.  Current thinking is thunderstorms will struggle to
   develop across much of TX due to significant CINH and this should
   allow air mass to destabilize across the MDT risk region as surface
   temperatures warm to near 80F with near 70F dew points.  Forecast
   NAM soundings by early afternoon depict SBCAPE in excess of 3000
   J/kg across northeast TX where convection should initiate prior to
   frontal passage.  Shear profiles strongly favor supercells, though
   mid-level height falls and slightly backed mid-level flow could
   eventually lead to a more complex MCS as the trough ejects toward
   the Mid-south after dark.  Very large hail could accompany the
   supercells across the Arklatex region and tornadoes appear possible.
   Strong/severe convection should spread into the central Gulf States
   during the evening/overnight hours as entrance region of upper jet
   shifts into this region during the latter half of the period.

   ...Mid MS Valley...

   Southwest-northeast oriented squall line has evolved from eastern OK
   into southwest MO early this morning.  Models suggest this activity
   should be ongoing at the beginning of the period but possibly a bit
   farther east than deterministic data would suggest.  This early-day
   convection will certainly disrupt and overturn buoyancy across much
   of the mid Mississippi Valley.  It's not entirely clear how unstable
   MO/IL region will be ahead of this activity and forecast soundings
   suggest poor lapse rates and weak buoyancy.  For these reasons have
   lowered severe probs across much of IL/MO due to limited
   instability.  Otherwise, forced squall line could certainly produce
   isolated severe wind gusts but the more robust convection should
   remain across the Ozark Plateau and points south.

   ..Darrow/Leitman.. 04/26/2017

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z