Jun 23, 2018 1630 UTC Day 1 Convective Outlook
Updated: Sat Jun 23 16:47:39 UTC 2018 (20180623 1630Z Day 1 shapefile | 20180623 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180623 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 285,063 44,248,714 Philadelphia, PA...Dallas, TX...Memphis, TN...Fort Worth, TX...Baltimore, MD...
MARGINAL 409,699 32,380,059 Charlotte, NC...Nashville, TN...Virginia Beach, VA...Raleigh, NC...Greensboro, NC...
Probabilistic Tornado Graphic
20180623 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 % 131,759 15,483,194 Baltimore, MD...Washington, DC...Oklahoma City, OK...Arlington, VA...Little Rock, AR...
Probabilistic Damaging Wind Graphic
20180623 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 % 271,625 43,260,036 Philadelphia, PA...Dallas, TX...Memphis, TN...Fort Worth, TX...Baltimore, MD...
5 % 430,337 36,114,067 Nashville, TN...Virginia Beach, VA...Raleigh, NC...Greensboro, NC...Durham, NC...
Probabilistic Large Hail Graphic
20180623 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
SIG SEVERE 27,525 724,469 Abilene, TX...Wichita Falls, TX...Lawton, OK...Duncan, OK...Altus, OK...
15 % 116,084 19,816,719 Dallas, TX...Fort Worth, TX...Baltimore, MD...Washington, DC...Oklahoma City, OK...
5 % 350,657 21,217,660 Memphis, TN...Virginia Beach, VA...Norfolk, VA...Chesapeake, VA...Shreveport, LA...
   SPC AC 231647

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1147 AM CDT Sat Jun 23 2018

   Valid 231630Z - 241200Z


   Scattered severe thunderstorms are expected especially this
   afternoon and evening from the southern Plains to the lower
   Mississippi Valley and a portion of the Southeast States. Other
   severe storms are expected over the Middle Atlantic region and
   central High Plains.

   ...TN and lower MS Valley region today...
   The remnants of an overnight MCS, now moving into northwest AL and
   southern middle TN, will be accompanied by some threat for damaging
   winds about as far east as southeast TN and northwest GA through
   early afternoon, given a belt of 40+ kt flow near 700 mb (enhanced
   some by the MCV with the convection).  However, the widespread
   clouds/convection ongoing farther to the south in AL casts doubt of
   the degree of destabilization possible in advance of these storms. 
   Otherwise, additional strong/isolated severe storms could evolve
   from the ongoing central AL storms into GA, or develop this
   afternoon along the residual outflow from southeast AR into MS and
   eventually spread into central AL (along the southern fringe of the
   current storms).  Damaging outflow gusts will be the main threat.

   ...Northwest TX into southern OK this afternoon into early
   The outflow boundary from overnight and ongoing convection has
   consolidated immediately north of I-20 across north central and
   northeast TX, and the boundary may begin to retreat a little to the
   north across northwest TX this afternoon.  An influx of low-mid 70s
   boundary-layer dewpoints into the boundary, along with daytime
   heating and midlevel lapse rates near 9 C/km, will boost MLCAPE into
   the 3000-4000 J/kg range this afternoon.  This corridor will lie
   along the southern fringe of the stronger midlevel flow (near or
   above 30 kt), with some enhancement to low-level shear along the
   boundary.  The net result will be profiles sufficient for supercells
   where deep mixing reduces convective inhibition across northwest TX,
   and in the warm advection zone to the north into southern OK this
   afternoon/evening.  The strongest storms could produce isolated very
   large hail and damaging gusts.

   ...Chesapeake region this afternoon/evening...
   A midlevel trough over the upper OH Valley will progress
   east-northeastward to southern New England tonight.  Embedded speed
   maxima will continue to rotate around the southeast periphery of the
   trough and interact with a diffuse lee trough across VA.  The richer
   low-level moisture/buoyancy should remain near Chesapeake Bay
   through the afternoon, while mid-upper flow/shear will be sufficient
   for organized storms.  A few supercells will be possible, with a
   primary threat for a few damaging gusts.

   ...Central High Plains this afternoon through early tonight...
   Another midlevel trough is beginning to amplify and will move from
   the northern Rockies to WY/CO tonight.  Low-level moisture is
   returning northward across southeast CO in the wake of overnight
   convection, and profiles will become sufficient for supercells by
   this afternoon.  A few storms should form along the Palmer Divide,
   and potentially the Raton Mesa, and then spread east-southeastward
   over the Plains this evening.  There are still some concerns
   regarding storm coverage, but any supercells that form will be
   capable of producing large hail and damaging winds, and storms could
   grow into a small cluster and persist into early tonight.

   ..Thompson/Smith.. 06/23/2018