Sep 7, 2021 1730 UTC Day 2 Convective Outlook
Updated: Tue Sep 7 17:43:47 UTC 2021 (20210907 1730Z Day 2 shapefile | 20210907 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20210907 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 23,505 7,664,770 Allentown, PA...Albany, NY...Reading, PA...Bethlehem, PA...Scranton, PA...
MARGINAL 139,003 51,081,731 New York, NY...Philadelphia, PA...Baltimore, MD...Washington, DC...Virginia Beach, VA...
Probabilistic Tornado Graphic
20210907 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 % 18,534 4,462,803 Allentown, PA...Reading, PA...Bethlehem, PA...Scranton, PA...Schenectady, NY...
2 % 31,205 12,605,012 Philadelphia, PA...Baltimore, MD...Syracuse, NY...Columbia, MD...Albany, NY...
Probabilistic Damaging Wind Graphic
20210907 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 % 23,597 7,409,060 Allentown, PA...Reading, PA...Bethlehem, PA...Scranton, PA...Schenectady, NY...
5 % 139,828 51,440,088 New York, NY...Philadelphia, PA...Baltimore, MD...Washington, DC...Virginia Beach, VA...
Probabilistic Large Hail Graphic
20210907 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 % 116,311 39,104,330 Philadelphia, PA...Baltimore, MD...Washington, DC...Raleigh, NC...Newark, NJ...
   SPC AC 071743

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1243 PM CDT Tue Sep 07 2021

   Valid 081200Z - 091200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   EASTERN NEW YORK AND PENNSYLVANIA INTO NORTHERN NEW JERSEY...

   ...SUMMARY...
   Scattered strong to severe thunderstorms are expected across parts
   of the Northeast and Mid Atlantic Wednesday afternoon and evening.

   ...Mid Atlantic into the Northeast...
   An amplified upper air pattern will exist on Wednesday with a
   prominent high over the Four Corners states and a deep upper trough
   moving from the Great Lakes into the Northeast. 

   At the surface, a low is forecast to pivot from eastern Ontario into
   western Quebec, with a cold front extending south across central NY
   into eastern PA by late afternoon. Southerly surface winds will
   result in a northward advection of mid to possibly upper 60s F
   dewpoints from the Delmarva into NJ and possibly southeast PA.
   Low-level lapse rates will be steepest across WV/VA, with best
   overall theta-e from MD into eastern PA. Southerly 850 mb winds
   around 40 kt will aid SRH with effective values over 200 m2/s2 by
   00Z. 

   While hodographs will be favorable for rotating storms, one
   mitigating factor may be the warm layer near 700 mb which may
   negatively impact low-level buoyancy. That said, lift along the
   front may be deep enough to support a supercell threat, and a brief
   tornado or two will be possible. Scattered damaging gusts are
   expected as storms become linear along the front. Good CAM agreement
   exists with increasing storms between 21-00Z from eastern NY into
   eastern PA, with maximum storm coverage just after 00Z. The loss of
   heating will play a part in limiting the eastward extent of the
   severe risk.

   Farther south into VA and NC, ample buoyancy will exist but with
   marginal shear. Both marginal hail and wind gusts will be possible
   after 21Z, with storms most likely from southern VA into central NC.

   Winds aloft will be quite a bit weaker farther southwest into SC and
   GA, but storms will also be likely near a surface trough. A few
   strong wind gusts cannot be ruled out with activity that forms in
   this region during the late afternoon, but the severe risk appears
   limited due to weak lapse rates aloft as well as shear.

   ..Jewell.. 09/07/2021

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