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    Day 2 Outlook >
Sep 28, 2016 2000 UTC Day 1 Convective Outlook
Updated: Wed Sep 28 19:45:39 UTC 2016 (Print Version | 20160928 2000Z Day 1 shapefile | 20160928 2000Z Day 1 KML)
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 Forecast Discussion
   SPC AC 281945

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0245 PM CDT WED SEP 28 2016

   VALID 282000Z - 291200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON INTO
   TONIGHT ALONG AND EAST OF THE BLUE RIDGE MOUNTAINS THROUGH THE
   PIEDMONT OF THE CAROLINAS AND VIRGINIA...AND PERHAPS ADJACENT
   PORTIONS OF THE COASTAL PLAIN...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
   MID ATLANTIC STATES/CENTRAL APPALACHIANS REGION...

   ...SUMMARY...
   THUNDERSTORMS IMPACTING THE PIEDMONT OF THE CAROLINAS AND VIRGINIA
   LATE THIS AFTERNOON INTO TONIGHT WILL POSE A RISK FOR SEVERE
   WEATHER.  THIS INCLUDES THE POSSIBILITY FOR A TORNADO OR TWO...BUT
   LOCALLY STRONG SURFACE GUSTS AND HAIL APPEAR THE PRIMARY POTENTIAL
   HAZARDS.

   ...20Z OUTLOOK UPDATE...
   SOME TWEAKS TO PROBABILISTIC AND CATEGORICAL LINES HAVE BEEN MADE TO
   ACCOUNT FOR CURRENT TRENDS IN MODEL OUTPUT AND OBSERVATIONAL DATA. 
   CONSIDERABLE INSOLATION ACROSS THE CAROLINAS INTO SOUTHERN VIRGINIA
   APPEARS TO HAVE CONTRIBUTED TO CAPE OF 1000-1500 J/KG ALONG AND
   SOUTH OF A LINGERING FRONTAL ZONE EXTENDING ACROSS THE SOUTHERN
   DELMARVA PENINSULA AND SOUTHERN VIRGINIA...INTO THE MOUNTAINS OF
   SOUTHWEST VIRGINIA AND NORTH CAROLINA.  A RELATIVELY COOL/STABLE
   NEAR SURFACE LAYER NOW PRESENT TO THE NORTH OF THE FRONT SEEMS
   LIKELY TO HOLD THROUGH TONIGHT ACROSS MUCH OF NORTHERN
   VIRGINIA/CENTRAL AND EASTERN MARYLAND...WITH ANY SURFACE PRESSURE
   FALLS TO THE LEE OF THE APPALACHIANS FORECAST TO REMAIN WEAK AND
   CONFINED TO THE WESTERN CAROLINAS LATE THIS AFTERNOON...PERHAPS
   NORTHWARD INTO THE PIEDMONT OF CENTRAL VIRGINIA BY LATE EVENING.  

   SUBSTANTIVE MID-LEVEL HEIGHT FALLS...THE MID-LEVEL COLD CORE AND
   CORE OF STRONGER WINDS ALOFT ASSOCIATED WITH CLOSED LOW NOW DIGGING
   INTO THE MIDDLE OHIO VALLEY APPEAR LIKELY TO REMAIN CONFINED TO
   AREAS NEAR AND WEST OF THE CREST OF THE CENTRAL APPALACHIANS. 
   HOWEVER...DEEP LAYER SHEAR CURRENTLY APPEARS SUFFICIENT FOR
   ORGANIZED STORM DEVELOPMENT...INCLUDING SUPERCELLS...WHERE THE
   BOUNDARY LAYER HAS ALREADY DESTABILIZED ACROSS THE VIRGINIA AND
   CAROLINA PIEDMONT.  AND IT STILL APPEARS POSSIBLE THAT AN AREA OF
   MID-LEVEL FORCING FOR ASCENT PIVOTING AROUND THE PERIPHERY OF THE
   CLOSED LOW COULD AUGMENT STORM DEVELOPMENT TO THE EAST OF THE BLUE
   RIDGE MOUNTAINS BY THE 00-03Z TIME FRAME.  ALTHOUGH LOW-LEVEL WIND
   FIELDS/HODOGRAPHS ARE CURRENTLY RATHER MODEST TO WEAK...MODEL OUTPUT
   SUGGESTS A COINCIDING STRENGTHENING OF SOUTHERLY 850 MB WINDS  ALONG
   THE FRONTAL ZONE ACROSS SOUTH CENTRAL VIRGINIA... TO AROUND 30+ KT. 
   ASSOCIATED ENLARGEMENT OF LOW-LEVEL HODOGRAPHS COULD BE ACCOMPANIED
   BY SOME INCREASE IN TORNADIC POTENTIAL BEFORE BOUNDARY LAYER
   INSTABILITY WANES OVERNIGHT.

   ..KERR.. 09/28/2016

   .PREV DISCUSSION... /ISSUED 1128 AM CDT WED SEP 28 2016/

   ...MID ATLANTIC REGION...
   A LARGE UPPER LOW IS CURRENTLY CENTERED NEAR CHICAGO...TRACKING
   SOUTHWARD INTO THE MID MS AND OH VALLEYS.  CYCLONICALLY CURVED AND
   MODERATELY STRONG MID-LEVEL WINDS EXTEND FROM THE BASE OF THE TROUGH
   INTO THE MID-ATLANTIC REGION...WHERE A MOIST AND UNSTABLE AIR MASS
   IS IN PLACE.  INCREASING DAYTIME HEATING OVER PARTS OF MD/VA/NC IS
   LEADING TO POCKETS OF MODERATE CAPE AND THE LIKELIHOOD OF AFTERNOON
   THUNDERSTORM DEVELOPMENT.  

   EARLY INITIATION MAY OCCUR OVER PARTS OF EASTERN VA INTO NORTHEAST
   NC.  THIS ACTIVITY MAY INCLUDE ROTATING STORMS CAPABLE OF LOCALLY
   DAMAGING WIND GUSTS AND PERHAPS A TORNADO OR TWO.  PLEASE REFER TO
   MCD NUMBER 1738 FOR FURTHER DETAILS ON THIS REGION.

   BY MID-LATE AFTERNOON...SCATTERED THUNDERSTORMS ARE POSSIBLE
   THROUGHOUT THE SLIGHT RISK AREA.  MOST MODEL SOLUTIONS SUGGEST THAT
   SOUTHERLY LOW LEVEL WINDS STRENGTHEN JUST AFTER DARK...WHICH WOULD
   IN TURN INCREASE THE POSSIBILITY OF A FEW TORNADOES IN THE STRONGEST
   CELLS.  OTHERWISE...DAMAGING WINDS APPEAR TO BE THE MAIN THREAT.  

   ...OH VALLEY...
   THE CORE OF THE UPPER LOW WILL TRACK ACROSS PARTS OF IL/IND/OH THIS
   AFTERNOON...COINCIDENT WITH A POCKET OF COLD MID LEVEL TEMPERATURES
   AND VORTICITY ALOFT.  VISIBLE SATELLITE TRENDS SUGGEST THAT LITTLE
   IN THE WAY OF HEATING WILL OCCUR AHEAD OF THE SURFACE
   BOUNDARY...LIMITING DESTABILIZATION.  WHILE SCATTERED THUNDERSTORMS
   ARE EXPECTED IN THIS REGION...THE RISK OF LARGE HAIL APPEARS TO BE
   BELOW 5 PERCENT.  NEVERTHELESS SMALL HAIL AND FUNNEL CLOUDS ARE
   POSSIBLE IN THE STRONGER CORES THIS AFTERNOON.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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