Jun 21, 2015 0730 UTC Day 3 Severe Thunderstorm Outlook
Updated: Sun Jun 21 07:30:44 UTC 2015 (20150621 0730Z Day 3 shapefile | 20150621 0730Z Day 3 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20150621 0730 UTC Day 3 Outlook Graphic
Day 3 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 183,944 51,130,303 New York, NY...Philadelphia, PA...Columbus, OH...Baltimore, MD...Pittsburgh, PA...
MARGINAL 264,470 40,424,396 Indianapolis, IN...Boston, MA...Washington, DC...Cleveland, OH...St. Louis, MO...
Probabilistic Graphic
20150621 0730 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 3 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 179,897 49,907,412 New York, NY...Philadelphia, PA...Columbus, OH...Baltimore, MD...Pittsburgh, PA...
5 % 281,580 41,830,843 Indianapolis, IN...Boston, MA...Washington, DC...Cleveland, OH...St. Louis, MO...
   SPC AC 210730

   DAY 3 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0230 AM CDT SUN JUN 21 2015

   VALID 231200Z - 241200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF OH
   VALLEY...CNTRL APPALACHIAN MTNS...MID-ATLANTIC...NY AND NEW
   ENGLAND...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL AND
   NRN HIGH PLAINS...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE MID MS
   VALLEY...OH VALLEY...CNTRL AND NRN APPALACHIANS AND NEW ENGLAND...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL AND
   NRN HIGH PLAINS...

   ...SUMMARY...
   SEVERE THUNDERSTORMS WITH HAIL AND ISOLATED DAMAGING WIND GUSTS WILL
   BE POSSIBLE FROM THE OHIO VALLEY NORTHEASTWARD INTO THE CENTRAL AND
   NORTHERN APPALACHIAN MOUNTAINS ON TUESDAY. SEVERE THUNDERSTORMS WITH
   ISOLATED LARGE HAIL AND WIND DAMAGE WILL ALSO BE POSSIBLE IN THE
   CENTRAL AND NORTHERN HIGH PLAINS.

   ...OH VALLEY/CNTRL APPALACHIAN MTNS...
   AN UPPER-LEVEL TROUGH IS FORECAST TO MOVE INTO THE NERN STATES ON
   TUESDAY AS A COLD FRONT ADVANCES QUICKLY SEWD INTO THE CNTRL
   APPALACHIANS EXTENDING WWD INTO THE OH VALLEY. ALONG AND SOUTH OF
   THE BOUNDARY...SFC DEWPOINTS IN THE LOWER TO MID 70S F SHOULD RESULT
   IN A STRONGLY UNSTABLE AIRMASS BY AFTERNOON FROM PARTS OF THE MID-MS
   VALLEY EWD INTO THE UPPER OH VALLEY. ALTHOUGH LARGE-SCALE ASCENT IS
   FORECAST TO REMAIN WEAK ACROSS THIS CORRIDOR...THUNDERSTORMS COULD
   INITIATE ALONG THE BOUNDARY AS SFC TEMPS WARM DURING THE DAY AND
   LOW-LEVEL CONVERGENCE INCREASES ALONG THE BOUNDARY. IN ADDITION TO
   STRONG INSTABILITY...NAM FORECAST SOUNDINGS ACROSS THE OH VALLEY AT
   21Z ON TUESDAY SHOW UNIDIRECTIONAL WIND PROFILES WITH 30 TO 40 KT OF
   FLOW FROM 700 TO 500 MB. THIS MAY CREATE AN ENVIRONMENT SUPPORTIVE
   OF DAMAGING WIND GUSTS WITH MULTICELL LINE-SEGMENTS THAT ORGANIZE
   DURING THE LATE AFTERNOON AND EARLY EVENING. DUE TO WEAK LARGE-SCALE
   ASCENT...CONVECTION IS EXPECTED TO REMAIN SOMEWHAT ISOLATED ACROSS
   THE REGION.

   ...NRN APPALACHIAN MTNS/MID-ATLANTIC/NEW ENGLAND...
   AN UPPER-LEVEL TROUGH IS FORECAST TO MOVE EWD INTO NERN STATES ON
   TUESDAY AS A COLD FRONT ADVANCES EWD FROM THE LOWER GREAT LAKES INTO
   THE NRN APPALACHIAN MTNS. THE EXIT REGION OF A 60 TO 80 KT MID-LEVEL
   JET IS FORECAST TO OVERSPREAD NY AND NEW ENGLAND DURING THE EARLY
   AFTERNOON. THIS WILL CREATE STRONG DEEP-LAYER SHEAR PROFILES THAT
   COULD BE FAVORABLE FOR SEVERE STORMS AS SFC TEMPS WARM UP DURING THE
   DAY. THE MODELS SUGGEST THAT CONVECTION MAY BE ONGOING ALONG THE
   FRONT AT THE START OF THE PERIOD WITH AN MCS MOVING QUICKLY EWD
   ACROSS THE REGION DURING THE LATE MORNING AND EARLY AFTERNOON. AHEAD
   OF THE FRONT...A MOIST AIRMASS SHOULD BE IN PLACE WITH MODERATE
   INSTABILITY DEVELOPING BY MIDDAY. THIS COMBINED WITH FOCUSED
   LARGE-SCALE ASCENT AND STRONG DEEP-LAYER SHEAR MAY ENABLE
   THUNDERSTORMS THAT DEVELOP ALONG THE FRONT TO HAVE A WIND DAMAGE
   THREAT DURING THE EARLY TO MID AFTERNOON.

   ...CNTRL AND NRN HIGH PLAINS...
   ZONAL FLOW IS FORECAST ACROSS THE NCNTRL STATES ON TUESDAY AS A LEE
   TROUGH DEVELOPS FROM ERN MT SWD INTO ERN WY AND NERN CO. UPSLOPE
   FLOW AND SFC DEWPOINTS IN THE 50S AND LOW 60S F SHOULD RESULT IN AN
   AXIS OF MODERATE INSTABILITY ALONG THE LEE TROUGH BY AFTERNOON. IN
   SPITE OF LIMITED LARGE-SCALE ASCENT...THUNDERSTORMS MAY INITIATE IN
   THE HIGHER TERRAIN AS SFC TEMPS WARM AND THEN MOVE EWD ACROSS THE
   CNTRL AND NRN HIGH PLAINS DURING THE LATE AFTERNOON AND EARLY
   EVENING. FORECAST SOUNDINGS IN ERN WY AT 00Z/FRIDAY SHOW MLCAPE NEAR
   2000 J/KG WITH 45-50 KT OF 0-6 KM SHEAR. THIS SHOULD BE ENOUGH FOR
   AN ISOLATED SEVERE THREAT WITH SUPERCELL DEVELOPMENT POSSIBLE.
   SUPERCELLS MAY BE ACCOMPANIED WITH ISOLATED LARGE HAIL AND SEVERE
   WIND GUSTS.

   ..BROYLES.. 06/21/2015

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