Jul 28, 2021 1730 UTC Day 2 Convective Outlook
Updated: Wed Jul 28 17:19:33 UTC 2021 (20210728 1730Z Day 2 shapefile | 20210728 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20210728 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 159,632 50,927,679 New York, NY...Philadelphia, PA...Indianapolis, IN...Columbus, OH...Baltimore, MD...
MARGINAL 214,181 32,322,002 Cleveland, OH...St. Louis, MO...Toledo, OH...Fort Wayne, IN...Yonkers, NY...
Probabilistic Tornado Graphic
20210728 1730 UTC Day 2 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 2 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 56,855 26,093,150 Philadelphia, PA...Baltimore, MD...Washington, DC...Arlington, VA...Alexandria, VA...
2 % 113,986 39,352,268 New York, NY...Indianapolis, IN...Columbus, OH...Pittsburgh, PA...Cincinnati, OH...
Probabilistic Damaging Wind Graphic
20210728 1730 UTC Day 2 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 2 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 159,682 51,352,060 New York, NY...Philadelphia, PA...Indianapolis, IN...Columbus, OH...Baltimore, MD...
5 % 213,958 31,900,842 Cleveland, OH...St. Louis, MO...Toledo, OH...Fort Wayne, IN...Yonkers, NY...
Probabilistic Large Hail Graphic
20210728 1730 UTC Day 2 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 2 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 306,000 63,149,882 New York, NY...Philadelphia, PA...Indianapolis, IN...Columbus, OH...Baltimore, MD...
   SPC AC 281719

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1219 PM CDT Wed Jul 28 2021

   Valid 291200Z - 301200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OHIO
   VALLEY INTO THE MID-ATLANTIC STATES...

   ...SUMMARY...
   Thunderstorms associated with wind damage and a risk for a tornado,
   will be possible from the Ohio Valley, central Appalachians and
   Mid-Atlantic states on Thursday.

   ...Ohio Valley/Central Appalachians/Mid-Atlantic/Mid Mississippi
   Valley...
   Showers and thunderstorms will likely be ongoing Thursday morning
   across the southern Great Lakes in association with an MCV.  This
   mid-level feature embedded within northwesterly flow, is expected to
   result from a severe squall line over the western Great Lakes prior
   to the start of the period.  In the low levels, a surface low
   initially over the central Great Lakes will develop eastward into
   New England late Thursday night.  An attendant cold front will push
   southeast across a large part of the OH Valley with the trailing
   portion of the boundary extending into the central High Plains. 
   Considerable uncertainty remains regarding the evolution of
   convection from IN into PA through the early afternoon.  A myriad of
   possible scenarios are evident in the latest convection-allowing
   model guidance in terms of the details of storm redevelopment during
   the afternoon.  With those concerns stated, a moist airmass will
   extend from the Corn Belt eastward into the Mid-Atlantic states with
   60s and lower 70s F dewpoints.  Strong heating on the periphery of
   earlier cloud debris will result in a moderate to very unstable
   airmass (1000-3000 J/kg MLCAPE).  A belt of strong westerly 700-mb
   flow is forecast to overspread the upper OH Valley into the
   Mid-Atlantic states during the afternoon.  Several linear clusters
   or a combination of linear clusters and supercells are possible from
   the OH Valley into the Mid-Atlantic states.  Damaging gusts and
   tornadoes are possible with the more intense thunderstorms.  Lower
   storm coverage and weaker deep-layer shear farther west over IL/MO
   will likely limit storm organization and the overall risk for severe
   thunderstorms.  
    
   ...Central High Plains/Central Rockies...
   A large area of high pressure will be in place on Thursday from the
   central Rockies southeastward into the lower Mississippi Valley.  At
   the surface, flow from the southeast will allow for a corridor of
   maximized low-level moisture to set up across Nebraska during the
   afternoon. Moderate instability is expected to be in place across
   much of the moist airmass by afternoon. Thunderstorms that develop
   at the western edge of the instability corridor will move
   east-southeastward across the central High Plains.  Moderate
   deep-layer shear and steep mid-level lapse rates will make
   marginally severe storms possible, with a potential for hail and
   isolated wind damage.

   ..Smith.. 07/28/2021

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