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    Day 2 Outlook >
Aug 21, 2014 2000 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Thu Aug 21 20:05:54 UTC 2014 (Print Version | 20140821 2000Z Day 1 shapefile | 20140821 2000Z Day 1 KML)
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 Forecast Discussion
   SPC AC 212005

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0305 PM CDT THU AUG 21 2014

   VALID 212000Z - 221200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY INTO
   THE OH VALLEY...

   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PART OF THE MID-ATLANTIC
   STATES...

   ...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF SERN CA INTO
   SWRN AZ...

   ...SUMMARY...
   SCATTERED STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED FROM PORTIONS
   OF THE UPPER MISSISSIPPI VALLEY INTO THE OHIO VALLEY AND CENTRAL
   APPALACHIANS. DAMAGING WINDS AND LARGE HAIL ARE THE PRIMARY THREATS
   WITH THIS ACTIVITY. STORMS WITH LARGE HAIL AND STRONG WINDS WILL
   ALSO BE POSSIBLE ACROSS THE LOWER COLORADO RIVER VALLEY.  SCATTERED
   STRONG TO SEVERE STORMS WILL ALSO REMAIN POSSIBLE INTO THE EARLY
   EVENING ACROSS PORTIONS OF THE MIDDLE ATLANTIC STATES FROM SOUTHEAST
   PENNSYLVANIA INTO NORTHERN AND CENTRAL MARYLAND...WASHINGTON D.C. TO
   DELAWARE AND SOUTHERN NEW JERSEY.

   ...MID-ATLANTIC STATES...
   A SLIGHT RISK HAS BEEN INTRODUCED ACROSS THIS REGION AND INCLUDES
   THE METRO AREAS OF PHILADELPHIA...BALTIMORE AND THE DISTRICT OF
   COLUMBIA.  VAD WINDS SHOWED SOME STRENGTHENING OF WLY 500 MB WINDS
   /AT 35 KT/ ENHANCING BULK SHEAR FOR STORM ORGANIZATION EWD FROM AND
   INCLUDING SRN PA AND NRN MD.  MODERATE INSTABILITY ACROSS THIS
   REGION COMBINED WITH THE STRONGER BULK SHEAR IS EXPECTED TO SUPPORT
   ADDITIONAL STRONG TO SEVERE STORMS DEVELOPING AND SPREADING SEWD.  

   ...SRN MN/WRN WI...
   LOW-LEVEL STRATUS CLOUDS OVER PORTIONS OF CENTRAL MN INCLUDING THE
   NRN TWIN CITIES METRO AND WEST CENTRAL WI WILL TEND TO INHIBIT
   SURFACE HEATING/DESTABILIZATION THROUGH THE REST OF THE AFTERNOON. 
   TSTMS REMAIN POSSIBLE PER 4KM NAM AND 4KM NSSL MODELS WITHIN THE
   WARM SECTOR IN SRN MN.  THIS OUTLOOK HAS SHIFTED THE NRN PORTION OF
   THE SLIGHT RISK IN SRN MN AND WRN WI SWD A FEW COUNTIES.
     
   ...ERN KY/FAR SWRN VA...
   THE SLIGHT RISK HAS BEEN EXPANDED A LITTLE TO INCLUDE MORE OF SERN
   KY AND FAR SWRN VA GIVEN CONVECTIVE TRENDS AND SIMILAR VALUES OF
   MODERATE TO STRONG INSTABILITY PER OBJECTIVE ANALYSES.

   ...ERN AL AND WRN/CENTRAL GA...
   STORMS WILL CONTINUE TO DEVELOP ACROSS THESE REGIONS THROUGH THE
   AFTERNOON TO EARLY EVENING WHERE THE ENVIRONMENT HAS BECOME VERY
   UNSTABLE /MLCAPE EXCEEDING 3000 J PER KG/.  WEAK DEEP LAYER SHEAR
   WILL TEND TO LIMIT STORM ORGANIZATION...WITH STRONG WIND GUSTS BEING
   THE PRIMARY THREATS.

   ...REST OF THE FORECAST...
   NO OTHER SIGNIFICANT CHANGES HAVE BEEN MADE TO THIS OUTLOOK.

   ..PETERS.. 08/21/2014

   .PREV DISCUSSION... /ISSUED 1129 AM CDT THU AUG 21 2014/

   ...UPPER MS VALLEY THROUGH THE GREAT LAKES AND OH VALLEY...

   HEIGHTS WILL RISE AND SHORTWAVE RIDGING WILL BUILD EWD TOWARD THE
   GREAT LAKES. HOWEVER...SATELLITE DATA AND RUC ANALYSIS SHOW A COUPLE
   OF VORTICITY MAXIMA...ONE LOCATED OVER WI AND ANOTHER OVER WRN IA.
   WIDESPREAD CLOUDS AND THUNDERSTORMS DEVELOPING WITHIN ZONE OF WARM
   ADVECTION CONTINUES FROM IA AND WI THROUGH NRN IL AND SEWD THROUGH
   OH. CLOUD COVER IS MUCH MORE LIMITED IN WARM SECTOR TO THE SOUTH OF
   THIS ACTIVITY WHERE DEWPOINTS ARE AROUND 70F. DIABATIC WARMING WILL
   DESTABILIZE THE BOUNDARY LAYER THIS AFTERNOON WITH MLCAPE FROM
   2000-3000 J/KG LIKELY. POTENTIAL EXISTS FOR STORMS TO REDEVELOP AND
   INTENSIFY LATER OVER THE OH VALLEY TODAY AS MOIST SWLY INFLOW FROM
   THE DESTABILIZING WARM SECTOR INTERACTS WITH THE NW-SE ORIENTED
   CONVECTIVELY REINFORCED BAROCLINIC ZONE. STORMS MAY SUBSEQUENTLY
   EVOLVE INTO CLUSTERS AS THEY DEVELOP SEWD WITH A THREAT FOR ISOLATED
   DAMAGING WIND AND HAIL. OTHER STRONG TO SEVERE STORMS MAY DEVELOP
   FARTHER NORTH IN MN NEAR THE WARM FRONT-COLD FRONT INTERSECTION. 

   ...EXTREME SERN CA AND SWRN AZ...

   PER SATELLITE IMAGERY AND GPS PW DATA...A MOISTURE PLUME ORIGINATING
   FROM T.S. LOWELL HAS BEEN ENTRAINED INTO THE EASTERN FLANK OF A
   CLOSED LOW MOVING SLOWLY EAST TOWARD THE LOWER CO RIVER VALLEY. LIFT
   AND COLDER AIR ALOFT ACCOMPANYING THE MID/UPPER LOW...IN CONCERT
   WITH DIURNAL HEATING...WILL LIKELY RESULT IN A CORRIDOR OF GREATER
   DESTABILIZATION AND THUNDERSTORM DEVELOPMENT ACROSS THE LOWER CO
   RIVER VALLEY LATER TODAY. IN ADDITION TO LOCALLY STRONG WIND GUSTS
   GIVEN HIGH DCAPE...SPC HAIL MODEL APPLIED TO FORECAST SOUNDINGS FROM
   THE NAM AND WRF-ARW INDICATE THE POSSIBILITY OF SEVERE HAIL TO AT
   LEAST 1 INCH IN DIAMETER. WHILE THE AREAL EXTENT OF THE SEVERE STORM
   THREAT MAY  REMAIN CONFINED...ENVIRONMENT APPEARS SUFFICIENT ENOUGH
   TO WARRANT SLGT RISK 15 PERCENT HAIL/WIND PROBABILITIES.

   ...MID ATLANTIC AREA...

   BACKGROUND CYCLONIC FLOW AND WEAK DPVA AMIDST A PLUME OF RELATIVELY
   HIGH PW SHOULD FOSTER SCATTERED LOOSELY-ORGANIZED THUNDERSTORMS OVER
   NY/PA AND DELMARVA THIS AFTERNOON. A BELT OF SOMEWHAT STRONGER
   MID-LEVEL FLOW FORECAST FROM SOUTHEAST NY ACROSS PA/NJ MAY
   CONTRIBUTE TO SLIGHTLY MORE ORGANIZED/PERSISTENT STORMS IN THESE
   AREAS. WHILE A COUPLE OF STRONGER CONVECTIVE WIND GUSTS WILL BE
   POSSIBLE AROUND THE TIME OF PEAK HEATING...WEAK LAPSE RATES AND
   MODEST INSTABILITY SUGGEST THE SEVERE WIND GUST POTENTIAL SHOULD
   REMAIN LIMITED.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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