Aug 23, 2019 0600 UTC Day 1 Convective Outlook
Updated: Fri Aug 23 05:55:58 UTC 2019 (20190823 1200Z Day 1 shapefile | 20190823 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20190823 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 115,555 5,814,281 Virginia Beach, VA...Raleigh, NC...Norfolk, VA...Chesapeake, VA...Durham, NC...
MARGINAL 171,489 8,794,620 Charlotte, NC...Greensboro, NC...Winston-Salem, NC...Amarillo, TX...Fort Collins, CO...
Probabilistic Tornado Graphic
20190823 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
2 % 82,482 3,834,818 Virginia Beach, VA...Norfolk, VA...Chesapeake, VA...Richmond, VA...Newport News, VA...
Probabilistic Damaging Wind Graphic
20190823 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
15 % 115,784 5,805,715 Virginia Beach, VA...Raleigh, NC...Norfolk, VA...Chesapeake, VA...Durham, NC...
5 % 171,154 8,869,881 Charlotte, NC...Greensboro, NC...Winston-Salem, NC...Amarillo, TX...Fort Collins, CO...
Probabilistic Large Hail Graphic
20190823 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
15 % 51,554 343,747 Cheyenne, WY...Scottsbluff, NE...Sterling, CO...Fort Morgan, CO...Lamar, CO...
5 % 143,099 6,622,023 Virginia Beach, VA...Raleigh, NC...Norfolk, VA...Chesapeake, VA...Durham, NC...
   SPC AC 230555

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1255 AM CDT Fri Aug 23 2019

   Valid 231200Z - 241200Z


   Severe thunderstorms capable of large hail and damaging wind gusts
   are possible this afternoon and evening, mainly across eastern
   Wyoming/Colorado into western Nebraska/Kansas. Severe thunderstorms,
   mainly capable of damaging wind gusts, are also expected across
   portions of southeast Virginia into northeast North Carolina this
   afternoon and evening.


   An upper trough over the northeastern states will continue to lift
   east/northeast today. The associated surface cold front will extend
   from near the New England coast this morning, arcing southwest into
   northern VA and the lower OH/middle MS Valley vicinity. The western
   extent of the front will push southward and become a focus for
   strong to severe thunderstorm development across portions of
   southern VA into NC. Meanwhile, the upper shortwave trough over the
   western U.S. will slowly shift east across the Rockies to the High
   Plains. A lee trough and moist, upslope flow regime amidst upper
   level height falls will focus another round of strong to severe
   thunderstorms across portions of the High Plains. 

   Elsewhere, a very moist and unstable boundary layer will support
   sporadic downbursts from Oklahoma into portions of the South.
   Organized severe threat will be limited by weak flow and a lack of
   upper forcing for ascent as the area remains under the influence of
   lower-amplitude southern-stream flow.  

   ...High Plains...

   While the upper shortwave trough migrating across the region is not
   particularly strong, unseasonably moist conditions will spread north
   and west on southeasterly low-level flow. Surface dewpoints well
   into the 60s will envelop much of the Plains and extend as far west
   as eastern MT/WY/CO. At the same time, a surface trough will extend
   southward from eastern WY into the OK/TX Panhandles. Strong heating
   along the trough beneath very steep midlevel lapse rates  (7.5-8.5
   C/km) will result in MLCAPE from 1500-3500 J/kg. Scattered
   thunderstorms will develop near the higher terrain in CO/WY during
   the afternoon as weak ascent increases with the approach of the
   trough. Deep-layer flow will remain modest, but vertically veering
   profiles and stronger low level southeasterly flow will result in
   25-40 kt effective shear. This will aid in maintaining organized
   convection with eastward extent over the High Plains into the
   evening.  By 00z, a 25-35 kt southerly low level jet will develop,
   aiding in upscale growth of storm clusters. Various guidance is
   consistent in developing one or more bowing segments tracking
   east/southeast across parts of eastern WY/CO into western NE/KS.
   Initial convection could pose a large-hail threat as it remains
   semi-discrete moving off of the higher terrain. However, with time,
   cells and clusters are expected to organized into one or more bowing
   segments with an attendant increase in damaging wind potential
   during the evening hours. 

   The northward extent of severe potential will be limited across
   eastern MT/western ND as remnant overnight convection and cloud
   cover limit heating, resulting in capping concerns. Any convection
   that redevelops overnight tonight likely will be elevated. 

   ...Portions of Southern VA into the Carolinas...

   A very moist airmass (surface dewpoints in the 70s F) will reside
   across southeast VA into the Carolinas ahead of the
   southward-advancing cold front.  Deep-layer flow is not particularly
   strong, similar to the previous few days. However, guidance suggests
   a shortwave impulse will eject across the central Appalachians
   during the afternoon as the southern extent of the upper trough
   pivots across the area. This will result in a band of around 25-30
   kt midlevel flow and effective shear will increase modestly. As
   forcing increases both in relation to this shortwave impulse and the
   approaching front, strong destabilization will result in scattered
   thunderstorm development by midday.  Somewhat stronger flow compared
   to previous days in the presence of the cold front should allow for
   better organized storm clusters and possibly one or more bowing
   segments tracking eastward across southeast VA into central/eastern
   NC and possibly parts of SC, though deep layer weakens quickly with
   southward extent. Steep low-level lapse rates and PW values greater
   than 2 inches will further support organized damaging-wind potential
   during the afternoon and evening. While midlevel lapse rates will be
   modest, some stronger cells could produce hail as well.

   ..Leitman/Wendt.. 08/23/2019