Apr 22, 2017 1630 UTC Day 1 Convective Outlook
Updated: Sat Apr 22 16:23:31 UTC 2017 (20170422 1630Z Day 1 shapefile | 20170422 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170422 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 80,295 6,549,449 Birmingham, AL...Jackson, MS...Huntsville, AL...Chattanooga, TN...Roanoke, VA...
MARGINAL 191,585 26,794,231 Nashville, TN...New Orleans, LA...Virginia Beach, VA...Atlanta, GA...Raleigh, NC...
Probabilistic Tornado Graphic
20170422 1630 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
2 % 55,447 4,386,649 Jackson, MS...Huntsville, AL...Roanoke, VA...Decatur, AL...Danville, VA...
Probabilistic Damaging Wind Graphic
20170422 1630 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
15 % 79,678 6,437,837 Birmingham, AL...Jackson, MS...Huntsville, AL...Chattanooga, TN...Roanoke, VA...
5 % 192,588 26,906,918 Nashville, TN...New Orleans, LA...Virginia Beach, VA...Atlanta, GA...Raleigh, NC...
Probabilistic Large Hail Graphic
20170422 1630 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
15 % 65,233 5,184,995 Birmingham, AL...Jackson, MS...Huntsville, AL...Chattanooga, TN...Tuscaloosa, AL...
5 % 207,150 28,146,222 Nashville, TN...New Orleans, LA...Virginia Beach, VA...Atlanta, GA...Raleigh, NC...
   SPC AC 221623

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1123 AM CDT Sat Apr 22 2017

   Valid 221630Z - 231200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
   LOWER MISSISSIPPI AND TENNESSEE VALLEYS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER SOUTHERN
   VIRGINA AND NORTHERN NORTH CAROLINA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ELSEWHERE FROM
   LOUISIANA TO THE VIRGINIA/NORTH CAROLINA BORDER REGION...

   ...SUMMARY...
   A few severe thunderstorms capable of damaging wind gusts and large
   hail will be possible this afternoon and evening from Louisiana to
   the southeastern Virginia/North Carolina Tidewater region.  The
   best-organized potential appears to be from parts of Mississippi
   into western/northern Alabama and southern Tennessee, and over
   southern Virginia and extreme northern North Carolina.

   ...Mississippi and Tennessee Valleys...
   A well-defined vorticity maximum over Missouri is forecast by model
   guidance to move eastward over the Mississippi Valley tonight as the
   associated upper trough amplifies during the period.  A strong band
   of mid/upper level winds is located on the southern periphery of the
   system with a 60-70 kt mid-level jet streak progressing toward the
   lower Mississippi Valley.

   At the surface, a low near the Mississippi Delta will move slowly
   eastward across northern parts of Mississippi and Alabama through
   tonight, as a trailing cold front moves southeastward across the
   lower Mississippi Valley. A quasistationary front extending eastward
   from the low is forecast to sag slowly southward with time.

   Earlier clouds over northern/central Mississippi into northern
   Alabama and southern middle Tennessee have diminished substantially
   permitting stronger diabatic heating to occur in advance of the
   approaching cold front.  With surface temperature warming into the
   70s and dew point values in the low-mid 60s, further destabilization
   is likely in the pre-frontal environment with MLCAPE reaching
   1000-1500 J/kg this afternoon.  CAM guidance indicates stronger
   storms will develop along/ahead of the cold front during the early
   afternoon with activity spreading eastward through the evening
   hours.  Effective bulk shear of 35-40 kt will promote organized
   storm structures including isolated supercells. Stronger cells will
   be capable of producing mainly damaging wind gusts and severe hail.

   ...Southern Virginia/Northern North Carolina...
   The environment is undergoing strong diabatic heating over North
   Carolina where visible satellite imagery indicates few clouds, and
   low-level warming is spreading northward into far southern Virginia
   as cloud cover thins near an east-west frontal zone. Despite modest
   mid-level lapse rates, surface dew points in the low-mid 60s coupled
   with diurnal heating will result in further destabilization with
   MLCAPE near 1500 J/kg expected this afternoon.  Storms are beginning
   to develop at this time over northwest North Carolina and southwest
   Virginia within a weakly-capped environment.  Activity is expected
   to increase in coverage and intensity and spread/develop eastward
   during the afternoon with a few severe storms possible.  See
   Mesoscale Discussion 545 for more details.

   ..Weiss/Cook.. 04/22/2017

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