Jul 21, 2016 1730 UTC Day 2 Convective Outlook
Updated: Thu Jul 21 17:30:54 UTC 2016 (20160721 1730Z Day 2 shapefile | 20160721 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20160721 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 166,202 11,777,968 Boston, MA...Worcester, MA...Springfield, MA...Hartford, CT...Manchester, NH...
MARGINAL 406,657 70,931,660 New York, NY...Chicago, IL...Philadelphia, PA...Detroit, MI...Denver, CO...
Probabilistic Graphic
20160721 1730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 2 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 166,159 11,777,114 Boston, MA...Worcester, MA...Springfield, MA...Hartford, CT...Manchester, NH...
5 % 406,863 70,921,144 New York, NY...Chicago, IL...Philadelphia, PA...Detroit, MI...Denver, CO...
   SPC AC 211730

   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1230 PM CDT THU JUL 21 2016

   VALID 221200Z - 231200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PART OF EASTERN NEW YORK
   INTO NEW ENGLAND...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTHERN PLAINS AND
   EASTERN MT...

   ...THERE IS A MRGL RISK OF SVR TSTMS EXTENDING WESTWARD ACROSS NY/NJ
   AND PA TO NORTHERN OH/INDIANA/IL AND SOUTHERN LOWER MI...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM PORTIONS OF THE NORTHERN
   AND CENTRAL HIGH PLAINS TO WESTERN MN AND CENTRAL IA...

   ...SUMMARY...
   SCATTERED SEVERE STORMS WILL BE POSSIBLE FRIDAY INTO FRIDAY EVENING
   ACROSS EASTERN NEW YORK AND NEW ENGLAND...WHILE ISOLATED STORMS
   STRONG TO SEVERE STORMS MAY OCCUR WESTWARD THROUGH PARTS OF NEW
   YORK...NEW JERSEY...AND PENNSYLVANIA TO THE SOUTHERN GREAT LAKES
   REGION.  ISOLATED TO SCATTERED SEVERE STORMS WILL BE POSSIBLE ACROSS
   THE NORTHERN PLAINS FRIDAY AFTERNOON INTO FRIDAY NIGHT.

   ...SYNOPSIS...
   A BELT OF MODERATELY STRONG MID-LEVEL FLOW ASSOCIATED WITH A
   SHORTWAVE TROUGH WILL NOSE INTO THE NORTHEASTERN U.S. LATE IN THE
   DAY AS A COLD FRONT PUSHES EWD THROUGH NEW ENGLAND PRIMARILY FRIDAY
   EVENING/NIGHT.  THE FRONT WILL EXTEND WESTWARD INTO THE SRN GREAT
   LAKES AND THIS REGION WILL RESIDE WITHIN THE NERN PERIPHERY OF A
   LARGE MID-LEVEL ANTICYCLONE CENTERED OVER THE CNTRL PLAINS.  FARTHER
   WEST...A SHORTWAVE TROUGH WILL MOVE FROM THE PACIFIC NW EWD INTO THE
   NRN NIGH PLAINS DURING THE PERIOD.  A SURFACE LOW WILL DEVELOP OVER
   MT AND MIGRATE TOWARDS THE SASKATCHEWAN/MT/ND BORDER BY DAYBREAK
   SATURDAY AS THE RESIDUAL FRONTAL SEGMENT ADVANCES NORTHWARD AS A
   WARM FRONT THROUGH THE NRN PLAINS.

   ...NORTHEAST...
   CONSIDERABLE UNCERTAINTY EXISTS REGARDING THE IMPACT OF DAY 1
   CONVECTION AND THE RESULTING INFLUENCE ON DESTABILIZATION ACROSS THE
   NORTHEAST STATES.  NONETHELESS...MODELS INDICATE LOW-LEVEL
   MOISTENING WILL OCCUR ON SOUTHERLY FLOW WHICH WILL CONTRIBUTE TO
   MODERATE BUOYANCY DEVELOPING IN AREAS VOID OF EARLY-DAY
   CLOUDS/PRECIP.  STRONG WESTERLY FLOW INCREASING WITH HEIGHT WILL
   SUPPORT THE NOTION FOR ORGANIZED STORMS /INCLUDING THE POSSIBILITY
   FOR SUPERCELL DEVELOPMENT AND MULTICELLS/ DEVELOPING PRIMARILY
   DURING THE AFTERNOON/EARLY EVENING.  ISOLD HAIL/WIND APPEAR TO BE
   THE MAIN HAZARDS WITH THE MORE INTENSE STORMS.  

   ...MT EWD INTO THE DAKOTAS AND N-CNTRL HIGH PLAINS...
   THE APPROACHING SHORTWAVE TROUGH WILL CONTRIBUTE TO WEAK H5 HEIGHT
   FALLS /30 M PER 12 HR/ ACROSS MT INTO THE WRN DAKOTAS BY 00Z AND
   WILL CONTRIBUTE TO SURFACE CYCLOGENESIS AND STRENGTHENING SELY
   LOW-LEVEL FLOW.  THE NORTHEASTWARD ADVECTION OF A N-CNTRL U.S.
   ELEVATED MIXED LAYER WILL OVERSPREAD A CAPPED BUT INCREASINGLY MOIST
   BOUNDARY LAYER.  STEEPENING LAPSE RATE PROFILES COUPLED WITH HEATING
   WILL YIELD MODERATE TO STRONG DESTABILIZATION.  VEERING AND
   STRENGTHENING WIND PROFILES WITH HEIGHT /40-KT MID-LEVEL WESTERLIES/
   WILL FAVOR ORGANIZED STORM DEVELOPMENT.  ISOLD TO WIDELY SCTD STORMS
   ARE FORECAST TO DEVELOP DURING THE LATE AFTERNOON/EARLY EVENING WITH
   ONLY ISOLD STORM COVERAGE EXPECTED FARTHER S IN THE N-CNTRL HIGH
   PLAINS.  A CLUSTER OR TWO OF STORMS MAY EVOLVE AS A STRENGTHENING
   WAA REGIME MAINTAINS A RISK FOR ISOLD SEVERE STORMS DURING THE
   OVERNIGHT AS ACTIVITY MOVES EWD ACROSS THIS REGION.  

   ...SRN GREAT LAKES...
   AMPLE HEATING DURING THE EARLY PART OF THE DAY AND A VERY MOIST
   AIRMASS /LOWEST 100-MB MEAN MIXING RATIOS 17-20 G PER KG/ WILL
   CONTRIBUTE TO A VERY UNSTABLE TO EXTREMELY UNSTABLE BOUNDARY LAYER. 
   THIS REGION WILL LIKELY RESIDE IN WAKE OF THE NORTHEAST U.S. TROUGH
   AND WELL REMOVED FROM THE N-CNTRL U.S. UPPER TROUGH.  YET...DESPITE
   WEAKENING CONVERGENCE ALONG THE FRONT...STRONG HEATING AND WEAK CINH
   WILL PROBABLY RESULT IN ISOLD SEVERE STORMS.  THIS ACTIVITY WILL
   LIKELY WEAKEN BY EARLY EVENING.

   ...ERN SD AND NERN NEB INTO IA...
   MODEL GUIDANCE SUGGESTS A LOW PROBABILITY FOR ISOLD STORMS TO
   DEVELOP NEAR THE FRONT DURING THE 22-02Z PERIOD.  IF STORMS MANAGE
   TO DEVELOP...A CORRESPONDING RISK FOR HAIL/WIND WOULD LIKELY
   ACCOMPANY THE STRONGER STORMS GIVEN LARGE BUOYANCY.  THE GREATER
   RISK FOR ISOLD STRONG/SEVERE STORMS APPEARS TO BE FOCUSED AFTER DARK
   AS THE TERMINUS OF A NOCTURNALLY STRENGTHENING CNTRL PLAINS LLJ
   INCREASES ISENTROPIC LIFT FRIDAY NIGHT.  ISOLD TO WIDELY SCATTERED
   STORMS ARE POSSIBLE AND MAY YIELD A WIND/HAIL THREAT.

   ...LOWER MS VALLEY AND AL...
   SCATTERED DIURNALLY DRIVEN STORMS ARE FORECAST TO DEVELOP BY
   EARLY-MID AFTERNOON.  STRONG BUOYANCY /2000 J PER KG MLCAPE/ AND
   HIGH BOUNDARY-LAYER MOISTURE CONTENT /LOW-MID 70S DEWPOINTS WILL
   SUPPORT VIGOROUS UPDRAFT DEVELOPMENT AND WATER-LOADED DOWNDRAFTS. 
   WEAK TROPOSPHERIC SHEAR WILL RESULT IN PULSE THUNDERSTORMS.  WILL
   REFRAIN FROM INTRODUCING LOW PROBABILITIES UNTIL CONFIDENCE
   INCREASES WHERE THE GREATEST CONCENTRATION OF STORMS AND PRIOR-DAY
   CONVECTIVE OVERTURNING INFLUENCES STRONGER STORM DEVELOPMENT.

   ..SMITH.. 07/21/2016

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