Jul 20, 2018 1730 UTC Day 2 Convective Outlook
Updated: Fri Jul 20 17:35:46 UTC 2018 (20180720 1730Z Day 2 shapefile | 20180720 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180720 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 170,756 22,135,064 Charlotte, NC...Atlanta, GA...Birmingham, AL...Montgomery, AL...Columbus, GA...
MARGINAL 263,766 27,291,631 Nashville, TN...Raleigh, NC...Greensboro, NC...Durham, NC...Winston-Salem, NC...
Probabilistic Graphic
20180720 1730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 2 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 169,766 22,049,433 Charlotte, NC...Atlanta, GA...Birmingham, AL...Montgomery, AL...Columbus, GA...
5 % 264,484 27,386,595 Nashville, TN...Raleigh, NC...Greensboro, NC...Durham, NC...Winston-Salem, NC...
   SPC AC 201735

   Day 2 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   1235 PM CDT Fri Jul 20 2018

   Valid 211200Z - 221200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE SOUTHEAST...AND ALSO NORTHEAST MT...

   CORRECTED FOR GEOGRAPHIC DESCRIPTION IN SUMMARY

   ...SUMMARY...
   Severe thunderstorms are possible Saturday, mainly during the
   afternoon and evening, across parts of the Southeast through the
   southern Appalachians and adjacent portions of the Piedmont. Severe
   thunderstorms will also be possible during the afternoon and evening
   across northeast Montana.

   ...Synopsis...
   An anomalous deep-layer cyclone is expected to move slowly
   southeastward into the Ohio Valley on Saturday. A surface boundary
   will progress into portions of the Southeast, with other
   convectively-induced boundaries likely to be present during the day.
   An embedded vorticity maximum off of the Carolina coast will be
   moving northeastward up the Atlantic Coast through the period,
   resulting in the development of a compact coastal low that will be
   approaching southern New England by Sunday morning. Further west, an
   upper trough and associated surface low will move eastward across
   the southern Canadian Prairies, with a trailing cold front expected
   to push into the northern High Plains. 

   ...Southeast into the Ohio Valley...
   Widespread intense convection during the D1/Friday period casts a
   considerable amount of uncertainty regarding the distribution of
   instability on Saturday across the Southeast into the Ohio Valley.
   However, with seasonably strong northwesterly flow and some remnant
   of the EML likely to be in place, pockets of moderate-to-strong
   instability and effective shear are expected to develop by Saturday
   afternoon across portions of the Southeast. A few supercells capable
   of large hail and localized damaging winds will be possible with
   initial development, followed by the potential for one or more
   upscale-growing clusters with a more organized wind threat. Due to
   considerable uncertainty regarding the coverage and location of
   potential redevelopment on Sunday afternoon, a relatively broad 15%
   area is maintained in this outlook. 

   ...Northern High Plains...
   A conditionally favorable environment for supercells is expected to
   develop on Saturday afternoon across eastern MT into northeast WY
   and perhaps SD, as low-level southeasterly  flow advects moisture
   underneath steep lapse rates aloft, and effective shear increases
   with the approach of stronger midlevel flow ahead of the trough.
   Large-scale forcing is expected to largely remain north of the
   border, but at least isolated thunderstorms are possible along a
   surface trough in eastern MT, and also developing across the higher
   terrain of eastern WY/western SD. Any storms that develop in this
   region would pose a risk of large hail and severe wind gusts, and
   perhaps a tornado or two. 

   ...Coastal Mid Atlantic into Southern New England...
   As the coastal low moves northeastward, low-level hodographs will
   lengthen substantially across portions of the Mid Atlantic coast
   into southern New England by Sunday morning. Surface-based
   instability will negligible until very near the end of the period,
   but some brief strong wind gust and/or tornado threat may
   materialize Sunday morning across portions of the NJ/DE coast into
   Long Island and coastal southern New England.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   2%     - Marginal
   Wind:     15%     - Slight
   Hail:     15%     - Slight

   ..Dean/Dial.. 07/20/2018

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z