Oct 20, 2016 2000 UTC Day 1 Convective Outlook
Updated: Thu Oct 20 20:00:14 UTC 2016 (20161020 2000Z Day 1 shapefile | 20161020 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20161020 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 21,427 3,493,993 Pittsburgh, PA...Altoona, PA...State College, PA...Mount Lebanon, PA...Bethel Park, PA...
MARGINAL 125,035 12,614,027 Nashville, TN...Lexington-Fayette, KY...Jackson, MS...Knoxville, TN...Huntsville, AL...
Probabilistic Tornado Graphic
20161020 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
5 % 5,190 389,982 State College, PA...Williamsport, PA...Lock Haven, PA...
2 % 16,191 2,877,896 Pittsburgh, PA...Altoona, PA...Mount Lebanon, PA...Bethel Park, PA...Elmira, NY...
Probabilistic Damaging Wind Graphic
20161020 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 % 21,241 3,463,740 Pittsburgh, PA...Altoona, PA...State College, PA...Mount Lebanon, PA...Bethel Park, PA...
5 % 125,080 12,669,488 Nashville, TN...Lexington-Fayette, KY...Jackson, MS...Knoxville, TN...Huntsville, AL...
Probabilistic Large Hail Graphic
20161020 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
5 % 133,659 14,455,477 Nashville, TN...Pittsburgh, PA...Lexington-Fayette, KY...Jackson, MS...Knoxville, TN...
   SPC AC 202000

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0300 PM CDT THU OCT 20 2016

   VALID 202000Z - 211200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM NRN WV THROUGH CNTRL PA...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE LOWER MS VALLEY
   THROUGH THE SWRN NY...

   ...SUMMARY...
   A FEW SEVERE STORMS REMAIN POSSIBLE THIS AFTERNOON AND EVENING FROM
   SOUTHWEST NEW YORK TO PARTS OF THE LOWER MISSISSIPPI VALLEY. IT
   STILL APPEARS GREATEST POTENTIAL FOR SEVERE WEATHER WILL BE FROM
   NORTHERN WEST VIRGINIA THROUGH CENTRAL PENNSYLVANIA.

   ...WV THROUGH CNTRL PA...

   ONLY MODEST ADJUSTMENTS HAVE BEEN MADE TO PREVIOUS OUTLOOK. WARM
   FRONT EXTENDS FROM A WEAK SFC LOW NEAR OH/PA BORDER EWD THROUGH
   CNTRL PA. COLD FRONT...A PORTION OF WHICH HAS BEEN CONVECTIVELY
   REINFORCED...EXTENDS SWWD FROM THE LOW THROUGH SE OH INTO CNTRL KY
   AND TN. SCATTERED THUNDERSTORMS WILL CONTINUE DEVELOPING ALONG COLD
   FRONT AS WELL AS AXIS OF PRE-FRONTAL CONVERGENCE LOCATED ACROSS WRN
   PA AND WV. STORMS SHOULD UNDERGO SOME INTENSIFICATION/ORGANIZATION
   WHERE THE BOUNDARY LAYER HAS DESTABILIZED WITH 75-80F SFC
   TEMPERATURES FROM WV THROUGH CNTRL PA. BUOYANCY REMAINS LIMITED BY
   WEAK MID-LEVEL LAPSE RATES AND MODEST LOW-LEVEL MOISTURE AND THIS
   MIGHT SERVE AS A LIMITING FACTOR FOR A MORE ROBUST SEVERE EVENT.
   NEVERTHELESS...40-50 KT EFFECTIVE BULK SHEAR WILL SUPPORT A FEW
   SUPERCELL/BOWING STRUCTURES CAPABLE OF DAMAGING WIND GUSTS. A
   TORNADO OR TWO IS ALSO POSSIBLE MAINLY OVER CNTRL PA WHERE NEAR-SFC
   WINDS REMAIN BACKED IN VICINITY OF WARM FRONT RESULTING IN LARGER
   0-1 KM HODOGRAPHS.  FOR ADDITIONAL INFORMATION SEE SWOMCD 1802.

   ..DIAL.. 10/20/2016

   .PREV DISCUSSION... /ISSUED 1120 AM CDT THU OCT 20 2016/

   ...DISCUSSION...

   STRENGTHENING MID-LEVEL SPEED MAX IS FORECAST TO DIG SEWD ACROSS AR
   INTO NRN MS BY 21/12Z ALLOWING THE POSITIVE-TILT TROUGH OVER THE
   MIDDLE OF THE COUNTRY TO BECOME MORE NEGATIVELY TILTED BY THE END OF
   THE PERIOD.  AS THIS OCCURS...STRONG HEIGHT FALLS WILL SPREAD ACROSS
   THE MID-SOUTH INTO THE OH/TN VALLEY REGION AND THE ASSOCIATED SFC
   FRONT IS EXPECTED TO SHARPEN AFTER DARK BEFORE SURGING INTO THE
   APPALACHIANS LATE.  WHILE THE STRONGEST FORCING FOR ASCENT WILL LAG
   THE SLGT RISK REGION THIS AFTERNOON...LATEST VIS IMAGERY DEPICTS
   SUBSTANTIAL CLEARING FROM NRN WV INTO CNTRL PA...JUST WEST OF A
   WEDGE FRONT THAT HAS BACKED ACROSS THE DELMARVA/ERN PA REGION.  THIS
   POCKET OF CLEARING WILL BE THE PRIMARY FOCUS FOR ORGANIZED SEVERE
   THUNDERSTORMS LATER THIS AFTERNOON AS SFC-3KM LAPSE RATES CONTINUE
   TO STEEPEN.

   LATE MORNING RADAR DATA SUGGESTS SOME CONTINUITY EXISTS WITH
   CONVECTIVE CLUSTER THAT HAS PROGRESSED ACROSS THE LOWER OH VALLEY. 
   A SLOWLY EXPANDING PRECIP SHIELD IS ASSOCIATED WITH A CLUSTER OF
   WEAK TSTMS THAT IS NOW SPREADING ACROSS NRN KY INTO SRN OH.  THIS
   ACTIVITY SHOULD LIMIT SFC HEATING ACROSS MUCH OF OH.  FOR THAT
   REASON HAVE LOWERED SEVERE PROBS WHERE INSTABILITY MAY BE LIMITED.

   LATER THIS AFTERNOON...SCT CONVECTION SHOULD DEVELOP ALONG THE
   AFOREMENTIONED CORRIDOR OF STRONG HEATING...ESPECIALLY OVER CNTRL
   PA.  STORMS THAT MATURE IN THIS ENVIRONMENT WILL BE STRONGLY SHEARED
   AND COULD ATTAIN SUPERCELL CHARACTERISTICS...ESPECIALLY WHERE
   LOW-LEVEL FLOW REMAINS BACKED ALONG WRN FRINGE OF NEW ENGLAND
   ANTI-CYCLONE.  WHILE LOCALLY DAMAGING WINDS ARE THE PRIMARY
   THREAT...WILL CLOSELY MONITOR PORTIONS OF WRN/CNTRL PA FOR A
   LOCALIZED TORNADO THREAT.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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