Aug 4, 2015 2000 UTC Day 1 Convective Outlook
Updated: Tue Aug 4 19:53:17 UTC 2015 (20150804 2000Z Day 1 shapefile | 20150804 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20150804 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 78,425 12,047,575 Boston, MA...Providence, RI...Worcester, MA...Toms River, NJ...Manchester, NH...
MARGINAL 382,549 32,570,806 Philadelphia, PA...Baltimore, MD...Washington, DC...Kansas City, MO...Omaha, NE...
Probabilistic Tornado Graphic
20150804 2000 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 % 68,889 12,104,470 Boston, MA...Providence, RI...Worcester, MA...Alexandria, VA...Manchester, NH...
Probabilistic Damaging Wind Graphic
20150804 2000 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 % 80,793 12,010,743 Boston, MA...Providence, RI...Worcester, MA...Manchester, NH...Lowell, MA...
5 % 349,257 31,285,792 Philadelphia, PA...Baltimore, MD...Washington, DC...Kansas City, MO...Wichita, KS...
Probabilistic Large Hail Graphic
20150804 2000 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 % 81,097 12,360,437 Boston, MA...Providence, RI...Worcester, MA...Alexandria, VA...Manchester, NH...
5 % 348,813 30,973,032 Philadelphia, PA...Baltimore, MD...Washington, DC...Kansas City, MO...Wichita, KS...
   SPC AC 041953

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0253 PM CDT TUE AUG 04 2015

   VALID 042000Z - 051200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON FROM SE NEW
   ENGLAND TO ERN MAINE...

   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR
   PARTS OF THE MID ATLANTIC...

   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR SW
   NEB AND WRN KS...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM PARTS OF VA TO ERN NY...

   ...THERE IS A MRGL RISK OF SVR TSTMS FOR PARTS OF THE CENTRAL PLAINS
   AND NRN HIGH PLAINS...

   ...SUMMARY...
   A FEW SEVERE THUNDERSTORMS WITH LARGE HAIL AND DAMAGING WINDS WILL
   CONTINUE THIS AFTERNOON ACROSS SOUTHEAST NEW ENGLAND AND EASTERN
   MAINE...AS WELL AS INTO LATE EVENING ACROSS WESTERN KANSAS.  A MORE
   ISOLATED AND MARGINAL SEVERE STORM RISK CONTINUES FOR SURROUNDING
   AREAS IN THE NORTHEAST STATES AND ACROSS THE PLAINS.

   ...NEW ENGLAND THIS AFTERNOON...
   ISOLATED SUPERCELLS ARE ONGOING ACROSS SE NH AND CENTRAL/ERN
   MA...AND THESE STORMS HAVE A HISTORY OF PRODUCING LARGE HAIL AND
   TREE DAMAGE.  THE STORM ENVIRONMENT REMAINS FAVORABLE FOR SUPERCELLS
   WITH SUBSTANTIAL DEEP-LAYER VERTICAL SHEAR /EFFECTIVE SHEAR AOA 50
   KT/ AND MODERATE BUOYANCY /MLCAPE 1500-2000 J PER KG/.  LOW-LEVEL
   SHEAR IS RELATIVELY WEAK...THOUGH AN ISOLATED TORNADO CANNOT BE
   RULED OUT WITH THE CENTRAL MA STORM CLUSTER MOVING ALONG THE OUTFLOW
   BOUNDARY FROM A LEAD STORM N OF BOSTON.  OTHERWISE...THE HAIL/WIND
   RISK WILL CONTINUE FOR THE NEXT FEW HOURS ACROSS SE NEW ENGLAND AND
   ERN MAINE BEFORE CONVECTIVE OVERTURNING AND THE LOSS OF DAYTIME
   HEATING REDUCE BUOYANCY.

   ...MID ATLANTIC THIS AFTERNOON/EVENING...
   DEEPER CUMULUS CONVECTION HAS BEEN RELEGATED TO THE BLUE RIDGE THUS
   FAR...BUT STRONG SURFACE HEATING/MIXING SHOULD STILL ALLOW A FEW
   STORMS TO SPREAD E OF THE MOUNTAINS THIS AFTERNOON ACROSS VA. 
   MODERATE CAPE AND EFFECTIVE BULK SHEAR OF 35-40 KT WILL BE
   SUFFICIENT FOR ORGANIZED MULTICELLS/SUPERCELLS CAPABLE OF PRODUCING
   AT LEAST ISOLATED LARGE HAIL AND DAMAGING WINDS.

   ...CENTRAL PLAINS THIS AFTERNOON/EVENING...
   CONVECTION HAS INCREASED IN COVERAGE/INTENSITY OVER SW NEB/NW KS
   THIS PAST COUPLE OF HOURS.  THE CONVECTION IS FOCUSED ALONG A
   STALLED SURFACE FRONT AND IMMEDIATELY IN ADVANCE OF A MIDLEVEL
   TROUGH OVER THE CENTRAL HIGH PLAINS...AND WILL LIKELY SPREAD SEWD AS
   A SMALL MCS.  AN ISOLATED TORNADO COULD OCCUR WITH THE INITIAL
   SUPERCELLS ON THE BOUNDARY IN NW KS WHERE LOW-LEVEL SHEAR IS
   STRONGER...THOUGH RATHER MODEST LOW-LEVEL MOISTURE ACROSS NW KS AND
   EXPECTED UPSCALE GROWTH OF THE STORMS SUPPORT THE PRIMARY RISKS OF
   LARGE HAIL AND DAMAGING WINDS THROUGH LATE EVENING.

   ..THOMPSON.. 08/04/2015

   .PREV DISCUSSION... /ISSUED 1127 AM CDT TUE AUG 04 2015/

   ...NEW ENGLAND...
   VISIBLE SATELLITE IMAGERY SHOWS AN INCREASING CU FIELD OVER MUCH OF
   NY AND NEW ENGLAND...WITH SCATTERED THUNDERSTORMS BEGINNING TO
   DEVELOP.  STRONG HEATING AND DEWPOINTS IN THE 60S WILL YIELD
   AFTERNOON MLCAPE VALUES OF 1000-1500 J/KG.  RATHER STRONG WESTERLY
   FLOW ALOFT AND FAVORABLE VERTICAL SHEAR PROFILES WILL PROMOTE
   DAMAGING WINDS AND HAIL IN THE STRONGER STORMS.  REFERENCE MCD 1605
   AND WW 469 FOR FURTHER DETAILS.

   ...MID ATLANTIC REGION...
   STRONG HEATING IS OCCURRING ACROSS THE MID ATLANTIC REGION...WHERE
   DEWPOINTS IN THE 60S TO NEAR 70F AND AFTERNOON HIGHS IN THE 90S WILL
   RESULT IN MODERATE CAPE VALUES.  AN INCREASING CU FIELD OVER THE
   MOUNTAINS OF WV/WESTERN VA MAY BE INDICATIVE OF DEEPER MIXING AND
   WILL LIKELY RESULT IN SCATTERED AFTERNOON THUNDERSTORMS.  THESE
   STORMS WILL SPREAD EASTWARD ACROSS THE DELMARVA REGION.  AFTERNOON
   FORECAST SOUNDINGS SHOW SUFFICIENT VERTICAL SHEAR AND STEEP LOW
   LEVEL LAPSE RATES TO POSE A RISK OF MULTICELL OR EVEN TRANSIENT
   SUPERCELL STORMS CAPABLE OF DAMAGING WINDS AND HAIL.

   ...CENTRAL/NORTHERN PLAINS...
   NO CHANGES HAVE BEEN MADE TO THE OUTLOOK FOR THIS REGION.  SCATTERED
   THUNDERSTORMS WILL BE POSSIBLE ALONG THE CORRIDOR FROM EASTERN MT
   INTO KS/MO TODAY...WITH POCKETS OF AFTERNOON HEATING RESULTING IN A
   FEW STRONG/SEVERE STORMS.  THE AREA SHOWING THE GREATEST POTENTIAL
   FOR ORGANIZED SEVERE LATER TODAY APPEARS TO BE PARTS OF NEB/KS.

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z