Sep 5, 2017 1630 UTC Day 1 Convective Outlook
Updated: Tue Sep 5 16:24:27 UTC 2017 (20170905 1630Z Day 1 shapefile | 20170905 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170905 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 62,313 16,749,960 Newark, NJ...Springfield, MA...Paterson, NJ...Manchester, NH...Waterbury, CT...
MARGINAL 266,768 62,389,125 New York, NY...Philadelphia, PA...Baltimore, MD...Charlotte, NC...Boston, MA...
Probabilistic Tornado Graphic
20170905 1630 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 % 57,453 15,774,851 Springfield, MA...Paterson, NJ...Manchester, NH...Allentown, PA...Albany, NY...
Probabilistic Damaging Wind Graphic
20170905 1630 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
15 % 62,278 16,705,487 Newark, NJ...Springfield, MA...Paterson, NJ...Manchester, NH...Waterbury, CT...
5 % 266,497 62,217,537 New York, NY...Philadelphia, PA...Baltimore, MD...Charlotte, NC...Boston, MA...
Probabilistic Large Hail Graphic
20170905 1630 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
15 % 28,313 3,583,514 Albany, NY...Scranton, PA...Schenectady, NY...Troy, NY...Pittsfield, MA...
5 % 99,081 25,211,996 Baltimore, MD...Washington, DC...Arlington, VA...Knoxville, TN...Springfield, MA...
   SPC AC 051624

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1124 AM CDT Tue Sep 05 2017

   Valid 051630Z - 061200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS
   AFTERNOON/EVENING FROM EASTERN PA INTO NEW ENGLAND...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
   TX TO NORTH GA...AND SURROUNDING THE SLIGHT RISK IN THE NORTHEAST...

   ...SUMMARY...
   Severe thunderstorms are possible especially this afternoon through
   early evening across portions of the Northeast and Mid-Atlantic
   States. Additional strong thunderstorms are possible ahead of a cold
   front extending across the northern Gulf coast states.

   ...Eastern PA into New England this afternoon/evening...
   A midlevel trough will continue to dig slowly south-southeastward
   over the MS and OH Valleys, as an associated surface cold front
   moves southward into the Gulf coast states and eastward across the
   Appalachians.  Deep-layer southwesterly flow will persist through
   the period downstream of the trough, from the Appalachians into New
   England, with a few embedded/subtle speed maxima enhanced by
   overnight convection.  

   Clouds from lingering convection are slowing surface heating from
   TN/KY to PA/NY, and destabilization has been hampered east of the
   Appalachians by a pocket of relatively dry air across the piedmont. 
   Thus, there is some uncertainty regarding the evolution of
   convection along the cold front through the afternoon, and it is
   possible that new development will be focused along the differential
   heating zone on the east edge of the thicker clouds.  Weak-moderate
   buoyancy (MLCAPE of 500-1500 J/kg) and effective bulk shear in
   excess of 40 kt will support a threat for damaging gusts and
   marginally severe hail with the stronger storms, some of which could
   have supercell structures.

   ...Northern Gulf coast states to the southern Appalachians...
   Scattered thunderstorms are expected this afternoon/evening along
   the surface cold front from northeast TX to north GA.  This corridor
   will remain a little south of the stronger midlevel flow, but
   isolated downbursts will be possible with multicell clusters in an
   environment with MLCAPE near 2000 J/kg and DCAPE near 1000 J/kg.

   ..Thompson/Cook.. 09/05/2017

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