Friday, April 10, 2009

Moderate Risk Expanded




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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