DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT FRI MAR 22 2013
VALID 231200Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE LOWER MS
VALLEY EWD ACROSS THE CENTRAL GULF COAST REGION...
...SYNOPSIS...
A WRN U.S. TROUGH WILL DIG SEWD FROM THE CENTRAL ROCKIES/FOUR
CORNERS INTO THE CENTRAL/SRN PLAINS DURING THE FIRST HALF OF DAY2.
THIS FEATURE WILL THEN TRACK EWD AND BEGIN TO TAKE ON A NEGATIVE
TILT BY 12Z SUN AS IT APPROACHES THE MID/LOWER MS VALLEY.
AS THE TROUGH DIGS EARLY IN THE PERIOD...A SURFACE LOW INITIALLY
OVER THE WRN HALF OF TX IS FORECAST TO REDEVELOP OVER THE LOWER MS
VALLEY DURING THE EVENING REACHING WRN TN BY 12Z SUN. AS THIS
OCCURS...A COLD FRONT IS FORECAST TO SURGE SEWD ACROSS THE SRN
PLAINS. MEANWHILE...GIVEN THE TRACK OF THE SYNOPTIC LOW AND BACKED
LOW LEVEL FLOW ACROSS THE NWRN GULF INTO THE LOWER MS VALLEY...A
WARM FRONT IS EXPECTED TO MAKE THE GREATEST NWD MOVEMENT ACROSS THE
WRN PART OF THE SLIGHT RISK AREA. FARTHER E...ONGOING ELEVATED
SHOWERS/EMBEDDED TSTMS WILL SHIFT EWD THROUGH THE SERN STATES...AND
COMBINED WITH EXTENSIVE CLOUDINESS SHOULD TEND TO MAINTAIN THE ERN
PART OF THE WARM FRONT ALONG OR JUST S OF THE FL PANHANDLE. THIS
PART OF THE FRONT SHOULD SHIFT NWD INTO SERN AL/SRN GA LATER SAT
NIGHT IN RESPONSE TO GREATER SURFACE PRESSURE FALLS INLAND OVER
CENTRAL/NRN GA.
...LOWER MS VALLEY AND CENTRAL GULF COAST REGION...
MODELS CONTINUE TO INDICATE THE SEVERE WEATHER POTENTIAL WILL BECOME
WIDESPREAD AND SUBSTANTIAL ENOUGH...MAINLY FROM LATE SAT AFTERNOON
THROUGH SAT NIGHT...TO MAINTAIN AN ENHANCED SLIGHT RISK AREA /UP TO
30 PERCENT SEVERE WEATHER PROBABILITY/ ACROSS THE LOWER MS VALLEY
AND CENTRAL GULF COAST STATES. SRN AL AND THE WRN FL PANHANDLE
REMAIN IN THIS ENHANCED THREAT AREA...ESPECIALLY FOR SAT NIGHT.
HOWEVER...LATEST GUIDANCE SUGGESTS GREATER UNCERTAINTY WITH THE
DEGREE OF DESTABILIZATION WITH NNEWD EXTENT IN AL SUCH THAT THE NRN
EXTENT OF THE 30 PERCENT PROBABILITY HAS BEEN SHIFTED S I-20.
THE AFOREMENTIONED BACKED LOW LEVEL FLOW INTO THE LOWER MS VALLEY
WILL SUPPORT MOISTURE RETURN BENEATH A PLUME OF STEEP MIDLEVEL LAPSE
RATES EXPECTED TO SPREAD EWD ACROSS THE GULF COAST REGION DURING
DAY2. DESPITE LIMITED SURFACE HEATING...MLCAPE OF 1000-1500 J/KG IS
EXPECTED ACROSS THE SRN EXTENT OF THE LOWER MS VALLEY WITH FURTHER
DESTABILIZATION FORECAST INLAND ACROSS CENTRAL/ERN MS AND SRN AL AS
THE WARM SECTOR ADVANCES FARTHER INLAND AFTER DARK. WEAKENING
INHIBITION WILL ALLOW FOR TSTMS TO DEVELOP ALONG THE WARM
FRONT...TRIPLE POINT AND SWD EXTENDING PRE-FRONTAL TROUGH BEING THE
PRIMARY FOCI. DEGREE OF INSTABILITY AND EFFECTIVE BULK SHEAR
EXCEEDING 50 KT WILL SUPPORT ORGANIZED STORMS.
IN ADDITION TO HEIGHT FALLS INCREASING SAT NIGHT FROM THE LOWER-MID
MS VALLEY EWD ACROSS THE GULF COAST STATES IN ADVANCE OF THE EWD
MOVING CENTRAL/SRN PLAINS UPPER TROUGH...FORCING FOR ASCENT WILL BE
ENHANCED INTO THE LOWER MS VALLEY/CENTRAL GULF COAST STATES. THIS
LATTER FACTOR WILL BE ATTENDANT TO DCVA SPREADING ACROSS THE WRN
EXTENT OF THE SLIGHT RISK AREA AFTER 24/00Z...AS A MIDLEVEL IMPULSE
TRANSLATES EWD THROUGH THE BASE OF THE PARENT LARGE SCALE TROUGH.
THIS COMBINED WITH ASCENT WITHIN THE EXIT REGION OF A 110-130 KT
WSWLY UPPER LEVEL JET SPREADING INTO SRN AL TO SRN GA LATE SAT NIGHT
WILL ALLOW FOR AN INCREASE IN TSTM DEVELOPMENT/COVERAGE WITH
ACTIVITY SPREADING EWD. STORM MODE MAY REMAIN MIXED EVEN INTO THE
OVERNIGHT PERIOD WITH ALL FACETS OF SEVERE WEATHER EXPECTED...WITH
GREATER COVERAGE FROM SRN AL TO SRN GA WHERE DEEP LAYER WIND FIELDS
WILL BE STRENGTHENING.
..PETERS.. 03/22/2013
