Jul 21, 2020 1730 UTC Day 2 Convective Outlook
Updated: Tue Jul 21 17:10:10 UTC 2020 (20200721 1730Z Day 2 shapefile | 20200721 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20200721 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 169,671 58,833,364 New York, NY...Philadelphia, PA...Columbus, OH...Baltimore, MD...Washington, DC...
MARGINAL 335,632 43,406,245 Detroit, MI...Indianapolis, IN...Boston, MA...Nashville, TN...Cleveland, OH...
Probabilistic Tornado Graphic
20200721 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
2 % 61,849 8,421,549 Worcester, MA...Springfield, MA...Syracuse, NY...Hartford, CT...Waterbury, CT...
Probabilistic Damaging Wind Graphic
20200721 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 % 169,831 58,968,004 New York, NY...Philadelphia, PA...Columbus, OH...Baltimore, MD...Washington, DC...
5 % 316,843 42,102,768 Detroit, MI...Indianapolis, IN...Boston, MA...Nashville, TN...Cleveland, OH...
Probabilistic Large Hail Graphic
20200721 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 % 162,479 42,836,255 New York, NY...Philadelphia, PA...Baltimore, MD...Newark, NJ...Lincoln, NE...
   SPC AC 211710

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1210 PM CDT Tue Jul 21 2020

   Valid 221200Z - 231200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE MID-ATLANTIC AND NORTHEAST STATES...

   ...SUMMARY...
   Strong to severe thunderstorms capable of producing mainly damaging
   winds may occur Wednesday across parts of the Northeast,
   Mid-Atlantic, Ohio Valley, and vicinity. Other isolated severe
   storms appear possible across parts of the central Plains.

   ...Ohio Valley into the Mid-Atlantic and Northeast...
   A shortwave trough will move quickly northeastward through the Upper
   OH Valley and Northeast on Wednesday. This shortwave is expected to
   dampen throughout the day as it enters the more confluent and
   stronger flow across the Northeast. Even so, the lingering
   southern/southwestern periphery of the shortwave trough will help
   force thunderstorms as it interacts with the moist and unstable air
   mass in place from the middle OH/TN Valleys into the Mid-Atlantic
   and Northeast.

   Bowing line segments and clusters should be the dominant storm mode,
   with damaging wind gusts as the predominant severe threat.
   Deep-layer vertical shear decreases with southern extent, so the
   highest potential for more organized storms, and perhaps even a few
   supercells, exists from central PA into Upstate NY/Southern New
   England. In this area, the stronger vertical shear suggest slightly
   greater potential for hail and maybe even a tornado or two.
   Antecedent cloud cover and possibly a few showers could inhibit
   destabilization in the vicinity of the warm front, but the stronger
   shear still merits including this area in a 15% wind probability.

   ...Central Plains/Central High Plains...
   Isolated thunderstorms will likely be ongoing early Wednesday
   morning near the western KS/NE border. An isolated hail/wind threat
   will exist with this early activity before it weakens throughout the
   morning. Additional storms are possible during the late
   afternoon/early evening on the outflow from this early activity.
   Isolated development is also possible a bit farther west along the
   lee trough. Any afternoon/evening storms that do develop may be
   strong enough to produce a strong wind gust or two.

   ...Northern CA...Southern OR...Northwest NV...
   Scattered thunderstorm activity is expected Wednesday afternoon in
   the vicinity of an upper low moving across northern/central CA and
   into western NV. Increased mid-level moisture and enhanced mid-level
   flow associated with this low will contribute to modest instability
   and vertical shear. Given the deeply mixed boundary layer and
   potential for a few stronger/more organized storms, a 5% severe wind
   probability was introduced for portions of northern CA, southern OR,
   and northwest NV.

   ..Mosier.. 07/21/2020

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