Sep 29, 2020 0600 UTC Day 1 Convective Outlook
Updated: Tue Sep 29 05:41:32 UTC 2020 (20200929 1200Z Day 1 shapefile | 20200929 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20200929 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 61,808 9,222,742 Virginia Beach, VA...Raleigh, NC...Norfolk, VA...Chesapeake, VA...Durham, NC...
Probabilistic Tornado Graphic
20200929 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 % 62,250 9,330,668 Virginia Beach, VA...Raleigh, NC...Norfolk, VA...Chesapeake, VA...Durham, NC...
Probabilistic Damaging Wind Graphic
20200929 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
5 % 61,669 9,222,757 Virginia Beach, VA...Raleigh, NC...Norfolk, VA...Chesapeake, VA...Durham, NC...
Probabilistic Large Hail Graphic
20200929 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
No Risk Areas Forecast
   SPC AC 290541

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1241 AM CDT Tue Sep 29 2020

   Valid 291200Z - 301200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   EASTERN CAROLINAS AND SOUTHEASTERN VIRGINIA...

   ...SUMMARY...
   Strong/locally severe thunderstorms capable of producing isolated
   damaging winds and possibly a tornado or two will be possible across
   the eastern Carolinas and into southeastern Virginia today.

   ...Synopsis...
   A highly amplified upper flow field -- featuring a western
   ridge/eastern trough configuration -- will persist across the U.S.
   today.  The primary trough axis -- initially aligned roughly from
   the Upper Great Lakes across the middle and lower Mississippi Valley
   -- will advance steadily eastward, crossing the Appalachians late in
   the period.

   At the surface, a cold front already in lee of the Appalachian Crest
   at the start of the period will move gradually eastward.  Overnight,
   the front will likely clear the middle and southern Atlantic Coasts,
   though lingering inland across New England through Wednesday
   morning. 

   ...Eastern Carolinas/southeastern Virginia...
   Widespread clouds/precipitation will be ongoing this morning at the
   start of the forecast period, ahead of the slowly advancing cold
   front.  Resulting weak lapse rates and hindered potential for
   daytime heating suggests meager CAPE across much of the pre-frontal
   warm sector.  With that said, strong -- albeit meridional and
   front-parallel -- flow aloft will exist across the region, though
   still yielding shear sufficient for organization within any updraft
   which can become sustained.

   The most likely area for sustained -- and thus potentially
   organized/rotating -- updrafts to occur still appears to exist
   across the eastern Carolinas and into southeastern Virginia.  Here,
   southerly flow advecting Gulf Stream moisture inland may support a
   local maximum in CAPE (500 to 700 J/kg), suggestive of slightly
   greater severe potential.  Therefore, will maintain the 5% wind/2%
   tornado area (MRGL categorical risk) across this region.  Elsewhere
   ahead of the front -- northward into New England and southward to
   Florida -- risk for severe weather appears lesser, though remaining
   non-zero until convection, and the associated cold front, move
   gradually offshore.

   ..Goss/Bentley.. 09/29/2020

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z