Oct 23, 2017 1630 UTC Day 1 Convective Outlook
Updated: Mon Oct 23 16:04:47 UTC 2017 (20171023 1630Z Day 1 shapefile | 20171023 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20171023 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 85,132 14,532,407 Charlotte, NC...Raleigh, NC...Greensboro, NC...Durham, NC...Winston-Salem, NC...
MARGINAL 125,342 23,654,434 Jacksonville, FL...Baltimore, MD...Washington, DC...Virginia Beach, VA...Norfolk, VA...
Probabilistic Tornado Graphic
20171023 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
5 % 58,666 11,854,110 Charlotte, NC...Raleigh, NC...Greensboro, NC...Durham, NC...Winston-Salem, NC...
2 % 113,965 20,337,857 Jacksonville, FL...Baltimore, MD...Washington, DC...Virginia Beach, VA...Norfolk, VA...
Probabilistic Damaging Wind Graphic
20171023 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 % 85,414 14,579,943 Charlotte, NC...Raleigh, NC...Greensboro, NC...Durham, NC...Winston-Salem, NC...
5 % 124,878 23,493,098 Jacksonville, FL...Baltimore, MD...Washington, DC...Virginia Beach, VA...Norfolk, VA...
Probabilistic Large Hail Graphic
20171023 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
No Risk Areas Forecast
   SPC AC 231604

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1104 AM CDT Mon Oct 23 2017

   Valid 231630Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   INTO TONIGHT FOR THE CAROLINAS AND SOUTHERN VA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTH FL TO
   THE MID ATLANTIC REGION...

   ...SUMMARY...
   Severe storms are possible from northern Florida to the Mid-Atlantic
   this afternoon and evening.  The primary threat will be damaging
   wind gusts, along with potential for a few tornadoes.

   ...Carolinas and vicinity through tonight...
   A midlevel shortwave trough over the TN Valley this morning will
   eject northeastward to the southern Appalachians this
   afternoon/evening, and continue north-northeastward to the central
   Appalachians and upper OH Valley tonight, in response to an
   amplifying upstream trough over the MS Valley.  An associated
   surface cyclone in central IN will move north-northeastward and
   deepen across Lower MI and the upper Great Lakes by tonight, as a
   trailing cold front progresses eastward to the southeast Atlantic
   coast and Mid-Atlantic region.  Ahead of the cold front, the moist
   warm sector will spread northward across NC today and VA by tonight,
   with the more unstable warm sector limited to areas east-southeast
   of a secondary low across western NC this afternoon/evening.

   Regional 12z soundings and radar/satellite imagery show a widespread
   band of clouds/rainfall preceding the cold front, where surface
   heating will be limited and lapse rates will remain rather poor. 
   Still, the rich low-level moisture (boundary-layer dewpoints of
   68-72 F) will contribute to weak surface-based buoyancy into the
   western Carolinas (SBCAPE 250-500 J/kg), and somewhat greater
   buoyancy into SC (1000-1500 J/kg).  At the same time, low-level
   shear will become quite strong (0-1 km SRH of 250-500 m2/s2), which
   will support strengthening of convection in a band with some breaks
   along the front this afternoon from eastern GA into the western and
   central Carolinas.  Embedded supercells and LEWP structures will be
   capable of producing a few tornadoes and damaging gusts, likely
   beginning by 18-20z in the vicinity of the Savannah River, and then
   spreading eastward-northeastward through this evening.

   Weaker low-level lapse rates and near-surface-based buoyancy will
   tend to limit the severe-storm threat with northward extent tonight
   into VA.  Still, a line of storms in the presence of very strong
   low-midlevel flow/shear and moist profiles will pose some threat for
   isolated damaging winds and a tornado or two.

   ..Thompson/Leitman.. 10/23/2017

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