Apr 10, 2009 1300 UTC Day 1 Convective Outlook
Updated: Fri Apr 10 12:50:20 UTC 2009
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the tennessee valley and southern appalachians this afternoon and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20090410 1300 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20090410 1300 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20090410 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20090410 1300 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 101246
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0746 AM CDT FRI APR 10 2009
   
   VALID 101300Z - 111200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF THE TN VLY/GULF
   CST STATES/SRN APPALACHIANS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA
   FROM MS AND THE LWR OH VLYS TO THE S ATLANTIC CST...
   
   ...SYNOPSIS...
   AMPLIFIED BUT PROGRESSIVE PATTERN WILL PERSIST ACROSS THE LWR 48
   THIS PERIOD.  MAIN FEATURE OF NOTE...POTENT UPR LOW NOW OVER SRN MO
   ...WILL CONTINUE E ACROSS SRN KY TODAY AND GRADUALLY DEVOLVE INTO AN
   OPEN WAVE.  THE SYSTEM SHOULD REACH SE VA BY 12Z SAT AS 80 KT MID
   LVL SPEED MAX NOW ON ITS SW PERIPHERY /OVER THE ARKLATEX/ MOVES OFF
   THE S ATLANTIC CST.
   
   AT LWR LEVELS...SFC LOW NOW OVER SE MO SHOULD TRACK E ACROSS KY
   TODAY/EARLY TONIGHT AS TRAILING COLD FRONT PROGRESSES STEADILY SE
   ACROSS THE TN/LWR MS VLYS.  AHEAD OF THE FRONT...SFC AND VWP DATA
   SUGGEST PRESENCE OF A PRE-FRONTAL LOW LVL CONFLUENCE AXIS...POSSIBLY
   RELATED TO SQLN OVER E TN/N GA...EXTENDING NE/SW FROM NRN AL INTO
   SRN MS.  FARTHER E...CURRENT OBSERVATIONS SUGGEST THAT WARM FRONT
   OVER THE SRN APPALACHIANS/CAROLINAS WILL REMAIN DIFFUSE THROUGH MUCH
   OF THE PERIOD.  BUT SIGNIFICANT LOW LVL WARMING/MOISTENING SHOULD
   SPREAD NE ALONG THE CAROLINA PIEDMONT/CSTL PLN WITH TIME AS SFC LOW
   REACHES SRN VA EARLY SATURDAY. 
     
   ...TN VLY INTO CNTRL GULF STATES...SRN APLCNS/CAROLINAS/SRN VA...
   LATEST SFC OBSERVATIONS AND SATELLITE/GPS PW DATA SHOW FAIRLY
   SUBSTANTIAL MOISTURE /WITH PW AOA 1 INCH/ IN PLACE FROM THE
   WRN/CNTRL GULF CST NE INTO THE TN VLY AND SRN KY.  A TONGUE OF DRIER
   AIR REMAINS PRESENT FROM FL NWD INTO THE WRN CAROLINAS...BUT A
   SECONDARY AREA OF ENHANCED MOISTURE LIES OFF THE NC CST.  MOISTURE
   SHOULD CONTINUE TO SPREAD NE ACROSS THE CNTRL/ERN GULF CST STATES
   AND GA TODAY AS 40+ KT SWLY LLJ PERSISTS IN WARM SECTOR OF
   PROGRESSIVE SFC LOW.  SFC DEWPOINTS IN THE LOW/MID 60S F SHOULD
   EXTEND FROM SRN LA INTO MUCH OF AL AND GA BY LATE TODAY.  
   
   COMBINATION OF INCREASING LOW LVL MOISTURE WITH COOL MID LVL
   TEMPERATURES AND ASCENT ON SRN FRINGE OF UPR LOW SHOULD SUPPORT
   INTENSE TSTM DEVELOPMENT LATER THIS MORNING THROUGH THIS AFTN 
   IN WEAKLY CAPPED ENVIRONMENT ALONG/AHEAD OF COLD FRONT FROM WRN
   KY/TN SSW INTO MS.  OTHER INTENSE STORMS SHOULD FORM NEARLY
   SIMULTANEOUSLY...OR PERHAPS SLIGHTLY LATER...INVOF AFOREMENTIONED
   CONFLUENCE ZONE OVER ERN MS/AL/GA.
   
   ALONG THE COLD FRONT...STRONG...LARGELY UNIDIRECTIONAL DEEP FLOW
   EXPECTED TO SUPPORT BROKEN BANDS OF SUSTAINED STORMS/SUPERCELLS WITH
   HIGH WIND/LARGE HAIL AND ISOLD TORNADOES.  FARTHER ESE...
   WEAKLY CONFLUENT LOW LVL FLOW AND LONG...CLOCKWISE-TURNING
   HODOGRAPHS WITH 60-70 KT WLY MID LVL FLOW COULD FOSTER NUMEROUS
   DISCRETE OR SEMI-DISCRETE SUPERCELLS...ESPECIALLY IN AREAS WHERE
   HEATING BOOSTS SFC TEMPERATURES TO NEAR 80 F.  THESE STORMS COULD
   YIELD A FEW STRONG TORNADOES...IN ADDITION TO VERY LARGE HAIL AND
   HIGH WIND.  THIS THREAT APPEARS GREATEST FROM CNTRL/NRN AL INTO
   CNTRL/NRN GA...PERHAPS AS FAR E AS WARM FRONTAL SEGMENT INVOF THE
   SAVANNAH RVR VLY THIS EVE.  
   
   LARGE SCALE UVV AHEAD OF UPR VORT SHOULD STRENGTHEN E OF THE SRN
   APPALACHIANS AND THE REMAINDER OF THE CAROLINAS/SRN VA BY LATER
   TONIGHT.  BUT...WEAKER DESTABILIZATION...ASSOCIATED WITH A MORE
   LIMITED LOW-LVL MOISTURE RETURN AND ONSET OF DIURNAL COOLING...MAY
   MITIGATE SVR POTENTIAL.  A LIMITED SVR THREAT
   COULD...HOWEVER...LINGER THROUGH EARLY SAT...ESPECIALLY ALONG THE NC
   CST.
   
   ..CORFIDI/JEWELL.. 04/10/2009
   
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