Apr 26, 2017 2000 UTC Day 1 Convective Outlook
Updated: Wed Apr 26 22:18:22 UTC 2017 (20170426 2000Z Day 1 shapefile | 20170426 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...Severe thunderstorms expected over parts of the lower Mississippi Valley this afternoon and tonight....   Please read the latest public statement about this event.  View What is a Watch? clip.

Categorical Graphic
20170426 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 68,108 4,033,911 Memphis, TN...Shreveport, LA...Longview, TX...Bossier City, LA...Jonesboro, AR...
SLIGHT 120,953 10,046,554 Indianapolis, IN...Birmingham, AL...Little Rock, AR...Jackson, MS...Evansville, IN...
MARGINAL 113,648 16,914,294 Nashville, TN...Fort Wayne, IN...Baton Rouge, LA...Montgomery, AL...Mobile, AL...
Probabilistic Tornado Graphic
20170426 2000 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 14,045 374,674 Pine Bluff, AR...El Dorado, AR...Camden, AR...Magnolia, AR...Stuttgart, AR...
10 % 25,832 1,235,759 Shreveport, LA...Bossier City, LA...Pine Bluff, AR...Monroe, LA...Greenville, MS...
5 % 60,384 3,853,703 Memphis, TN...Jackson, MS...Alexandria, LA...Bartlett, TN...Southaven, MS...
2 % 91,677 6,450,092 Baton Rouge, LA...Little Rock, AR...Lafayette, LA...Tuscaloosa, AL...Longview, TX...
Probabilistic Damaging Wind Graphic
20170426 2000 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 % 67,564 4,019,190 Memphis, TN...Shreveport, LA...Longview, TX...Bossier City, LA...Jonesboro, AR...
15 % 120,892 9,997,885 Indianapolis, IN...Birmingham, AL...Little Rock, AR...Jackson, MS...Evansville, IN...
5 % 113,852 16,841,351 Nashville, TN...Fort Wayne, IN...Baton Rouge, LA...Montgomery, AL...Mobile, AL...
Probabilistic Large Hail Graphic
20170426 2000 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 26,610 1,422,794 Shreveport, LA...Longview, TX...Bossier City, LA...Pine Bluff, AR...Monroe, LA...
30 % 21,949 1,136,364 Shreveport, LA...Bossier City, LA...Pine Bluff, AR...Monroe, LA...Greenville, MS...
15 % 83,740 4,993,745 Memphis, TN...Jackson, MS...Tyler, TX...Longview, TX...Alexandria, LA...
5 % 89,191 7,617,452 Baton Rouge, LA...Little Rock, AR...Lafayette, LA...Beaumont, TX...Tuscaloosa, AL...
   SPC AC 262218

   Day 1 Convective Outlook AMEND 1
   NWS Storm Prediction Center Norman OK
   0518 PM CDT Wed Apr 26 2017

   Valid 262210Z - 271200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE LOWER MS VALLEY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER MS
   VALLEY INTO INDIANA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
   THE MID AND LOWER MS VALLEY INTO THE SOUTHERN GREAT LAKES REGION...

   AMENDED FOR NORTHWARD ADJUSTMENT OF MARGINAL/SLIGHT AREAS IN THE
   SOUTHERN GREAT LAKES REGION

   ...SUMMARY...
   Severe thunderstorms will continue across the Lower Mississippi
   Valley.  Tornadoes, large hail, and damaging winds are most probable
   from northeast Texas across parts of Arkansas and northern Louisiana
   this afternoon and evening. Isolated severe thunderstorms may extend
   as far north as Illinois/Indiana this afternoon and evening, and
   into the central Gulf States during the overnight hours.

   ...2210Z Outlook Amendment...

   The Slight/Marginal areas have been extended northward across
   portions of the southern Great Lakes region.  Please reference
   Severe Thunderstorm Watch 165 for additional details.

   ...20Z Update...

   ...Lower MS Valley...
   Outflow boundary continues to surge eastward across northern and
   central AR ahead of the approaching cold front. Anafrontal character
   to the ongoing convection is expected to continue with the cold
   front eventually catching up to the outflow later this
   afternoon/evening. Farther south, a more composite outflow/cold
   front already exists with some severe storms currently ongoing.

   Linear nature of this convection is expected to persist throughout
   the evening with little indication in either recent observations
   (i.e. backed mid-level flow on the 18Z SHV sounding) or recent
   guidance that robust discrete development will occur.  As a result,
   reduced the tornado probabilities across the area to 10%. Given the
   strength of the shear, some QLCS tornadoes are still possible.

   Strongest storms are expected to remain along the southern end of
   the line where the best low-level moisture exists and the mean flow
   is more orthogonal to the advancing cold front. 

   ...OH Valley...
   Based on current convective trends, expanded the Slight a bit more
   northeastward into more east-central IL and southwest IN.

   ..Cohen.. 04/26/2017

   .PREV DISCUSSION... /ISSUED 1127 AM CDT Wed Apr 26 2017/

   ...Lower MS Valley...
   Few changes have been made to the ongoing forecast.  A squall line
   currently extends from south-central MO into northeast TX.  Several
   bowing structures along this line will pose a risk of damaging winds
   gusts, large hail, and perhaps a QLCS tornado or two this afternoon.
   The activity will likely spread into southeast MO and western KY/TN
   by early evening, with a continued severe threat.

   Farther south, most model solutions suggest that the capping
   inversion will slowly weaken this afternoon.  This should help to
   allow a few discrete storms to form in the warm sector ahead of the
   more organized convective line.  Local VAD and forecast hodographs
   in this region continue to support a risk of supercells capable of
   tornadoes (some strong) if discrete initiation materializes. 
   Therefore will maintain the MDT risk and 15% tornado forecast. 
   These storms are expected to track northeastward through the evening
   into western/central MS where damaging winds and isolated tornadoes
   will remain possible.

   Overnight, it is uncertain how far east the organized severe threat
   will persist.  Nevertheless, will make no changes to the eastern
   extent of the SLGT risk at this time.

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z