DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 232001
SWODY1
SPC AC 231958

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT SAT MAR 23 2013

VALID 232000Z - 241200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE SOUTHEAST
UNITED STATES...

...SRN GA/NRN FL WWD TO SRN AL/SERN MS THROUGH THE EVENING...
EARLY AFTERNOON SURFACE ANALYSIS INDICATED LITTLE NWD MOVEMENT OF
THE E-W ORIENTED WARM FRONT EXTENDING FROM SRN LA TO THE NRN FL
PENINSULA. THE EXCEPTION HAS BEEN THE PORTION OF THIS BOUNDARY
OFFSHORE MS/AL AND THE WRN FL PANHANDLE...WHERE TRENDS SUGGEST THE
FRONT HAS MOVED CLOSER TO THE COAST AND LIKELY EXTENDED ACROSS GULF
AND FRANKLIN COUNTIES FL. THE FORECAST ACROSS THESE AREAS OF THE
CENTRAL GULF COAST EWD TO NRN FL/SRN GA REMAINS ON TRACK...WITH THE
INITIAL CLUSTER OF STORMS MOVING OFF THE NERN FL COAST...WHILE
STORMS CONTINUE TO DEVELOP UPSTREAM AND TRACK EWD IN VICINITY AND N
OF THE WARM FRONT. A SLIGHT RISK FOR SEVERE STORMS WILL BE
MAINTAINED WITH THIS OUTLOOK ISSUANCE...WITH ADDITIONAL DETAILS
AVAILABLE IN VALID AND SUBSEQUENT MESOSCALE DISCUSSIONS RELEVANT TO
WW/S 57 AND 58.

A COUPLE STORMS...CURRENTLY LOCATED OFFSHORE THE NERN GULF
COAST...COULD PRODUCE VERY LARGE HAIL BOTH OVER THE WATER AND AS
THEY REACH THE FL COAST. STEEP MIDLEVEL LAPSE RATES...MODERATE
INSTABILITY AND EFFECTIVE BULK SHEAR OF 40-50 KT SUPPORT SUPERCELLS
AND THIS HAIL POTENTIAL...IN ADDITION TO DAMAGING WINDS AND A
TORNADO. THE LATTER THREAT WOULD BE GREATEST INVOF THE WARM FRONT
WHERE LOW LEVEL SHEAR IS STRONGEST /EFFECTIVE SRH 200-300 M2 PER
S2/.

...E TX/LA/MS...
AN INCREASE IN TSTM DEVELOPMENT APPEARS TO BE UNDERWAY ACROSS PARTS
OF E TX /REFERENCE MESOSCALE DISCUSSION 304/ IN RESPONSE TO LARGE
SCALE ASCENT SPREADING DOWNSTREAM AHEAD OF THE CO/NM SHORTWAVE
TROUGH AND AN APPARENT LEAD IMPULSE/JET STREAK ADVANCING EWD ACROSS
W TX. 12Z 4 KM WRF-NMM/NSSL SUGGEST THESE STORMS MAY EVOLVE INTO A
FORWARD PROPAGATING MCS ACROSS NRN LA THROUGH CENTRAL AND PARTS OF
SRN MS TO CENTRAL AL THIS EVENING INTO THE OVERNIGHT. GIVEN THE LACK
OF TSTM DEVELOPMENT THUS FAR OVER MUCH OF LA AND CENTRAL/SRN
MS...THIS AIR MASS WILL CONTINUE TO MOISTEN/DESTABILIZE INTO THE
EVENING WITH A WARM FRONT ADVANCING NWD. THIS OBSERVATIONAL DATA
SUPPORTS THE HIGHER RESOLUTION MODELS...AND THUS HAVE ADDED A 30
PERCENT SEVERE WIND PROBABILITY FROM NRN LA TO WEST CENTRAL AL. THE
WRF-NMM/NSSL ALSO SUGGEST THE ACTIVITY DEVELOPING AND TRACKING EWD
FROM NRN LA TO CENTRAL AL COULD BE A QLCS...AND THUS HAVE EXTENDED
THE 5 PERCENT TORNADO PROBABILITIES NWWD.

..PETERS.. 03/23/2013

.PREV DISCUSSION... /ISSUED 1130 AM CDT SAT MAR 23 2013/

A LARGE UPPER TROUGH IS PRESENT TODAY OVER THE WESTERN STATES...WITH
A SERIES OF SHORTWAVE TROUGHS ROTATING ACROSS THE SOUTHERN PLAINS
AND GULF COAST REGION. THUNDERSTORMS ARE EXPECTED TO BECOME MORE
NUMEROUS LATER TODAY FROM TX ACROSS THE GULF COAST STATES...WITH AN
INCREASING RISK OF LOCALLY SEVERE STORMS.

...FL/GA...
A LARGE CLUSTER OF INTENSE THUNDERSTORMS IS ONGOING OVER SOUTHERN GA
AND NORTH FL. THE STRONGEST OF THESE STORMS HAVE PRODUCED LARGE
HAIL. WEAK LOW LEVEL WARM ADVECTION AND LIFT WILL LIKELY MAINTAIN
THIS ACTIVITY FOR A FEW MORE HOURS AS IT SPREADS EASTWARD TOWARD THE
COAST. ANOTHER BAND OF CONVECTION APPEARS TO BE INTENSIFYING OFF
THE COAST OF THE FL PANHANDLE...ALONG A RETREATING WARM FRONT.
THESE STORMS MAY SPREAD INLAND LATER THIS AFTERNOON...CONTINUING THE
RISK OF LOCALLY SEVERE STORMS. SUFFICIENT LOW/MID LEVEL VERTICAL
SHEAR WILL BE PRESENT FOR A RISK OF SUPERCELLS CAPABLE OF ALL FACETS
OF SEVERE WEATHER. REFERENCE MCD NUMBER 299 FOR FURTHER DETAILS.

...LA/MS/AL...
A WARM FRONT CURRENTLY EXTENDS FROM SOUTHEAST TX...EASTWARD ACROSS
SOUTHERN LA INTO SOUTHERN MS. THIS BOUNDARY IS MAKING VERY LITTLE
PROGRESS NORTHWARD. NEVERTHELESS...BROKEN CLOUDS TO THE NORTH OF
THE BOUNDARY MAY RESULT IN DEEPER MIXING AND SOME NORTHWARD
PROGRESSION LATER TODAY. A WEAKENING CAP AND MODERATE INSTABILITY
WILL POSE A RISK OF SCATTERED THUNDERSTORM DEVELOPMENT BY MID-LATE
AFTERNOON. DESPITE RATHER WEAK FORCING MECHANISMS...SEVERAL MODEL
SOLUTIONS INDICATE A THREAT OF ENHANCED COVERAGE OF STRONG/SEVERE
STORMS. THEREFORE HAVE MAINTAINED THE 30 PERCENT HAIL RISK ACROSS
THIS REGION.

...TX/LA/MS LATER TONIGHT...
ANOTHER ROUND OF STRONG STORMS IS EXPECTED LATER TONIGHT AS THE MAIN
UPPER TROUGH MOVES INTO THE SOUTHERN PLAINS AND THE COLD FRONT
BEGINS TO SURGE EASTWARD. THESE STORMS WILL PROGRESS FROM EAST TX
INTO MS WITH A RISK OF DAMAGING WINDS AND HAIL.

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