DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 221957
SWODY1
SPC AC 221955

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0255 PM CDT FRI MAR 22 2013

VALID 222000Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF NORTHEAST
TX...NORTHERN LA...AND WESTERN MS...

...E TX/NRN AND CENTRAL LA/W-SWRN MS...
EARLY AFTERNOON SURFACE ANALYSIS SHOWED A LOW IN NERN TX /INVOF
KTYR/...WITH A WARM FRONT EXTENDING SEWD THROUGH WEST CENTRAL TO
SERN LA. MOISTENING AND SURFACE HEATING ACROSS THE WARM SECTOR WILL
CONTINUE TO SUPPORT LOW LEVEL DESTABILIZATION. THE LACK OF
SUFFICIENT WEAKENING OF SURFACE BASED INHIBITION PER OBJECTIVE
ANALYSES SUGGESTS THE STRONG CAP EVIDENT ON 12Z TX SOUNDINGS HAS
SPREAD EWD...INHIBITING DEEP MOIST CONVECTION DEVELOPMENT. WHILE
THE CAPE-SHEAR PARAMETER SPACE OVER E TX/WRN LA IS SUPPORTIVE OF
ORGANIZED STORMS --- IF THEY DEVELOP...THE LAST FEW RUNS OF THE HRRR
SUGGEST LOW CONFIDENCE IN TSTM INITIATION. GIVEN MLCAPE UP TO 1000
J/KG AND EFFECTIVE BULK SHEAR EXCEEDING 50 KT OVER THE WRN PART OF
THE SLIGHT...A CONDITIONAL RISK FOR SEVERE STORMS IS MAINTAINED INTO
THIS EVENING AND EARLY TONIGHT.

..PETERS.. 03/22/2013

.PREV DISCUSSION... /ISSUED 1127 AM CDT FRI MAR 22 2013/

...ARKLATEX...
WATER VAPOR LOOPS CONTINUE TO SHOW A PRONOUNCED UPPER TROUGH
DEVELOPING ACROSS THE GREAT BASIN...WHILE SHORTWAVE RIDGING OCCURS
OVER PORTIONS OF NM/TX. AT THE SURFACE...A WEAK LOW IS ANALYZED
NEAR DAL WITH A WARM FRONT EXTENDING EAST-SOUTHEASTWARD ACROSS EAST
TX INTO SOUTHERN LA. THE WARM FRONT IS FORECAST TO PROGRESS SLOWLY
NORTHWARD THROUGH THE DAY WITH A MOIST AND MODERATELY UNSTABLE AIR
MASS SPREADING INTO CENTRAL/NORTHERN LA AND PARTS OF WESTERN MS BY
EVENING. THESE FACTORS WILL RESULT IN A REGION OF CONDITIONAL RISK
FOR SEVERE THUNDERSTORMS THIS EVENING AND EARLY TONIGHT.

ONE OF THE MAIN FORECAST UNCERTAINTIES INVOLVES WEAK LARGE SCALE
ASCENT THAT WILL BE PRESENT OVER THE RISK AREA TODAY. WEAK LOW
LEVEL WARM ADVECTION IS OCCURRING...AND THIS LIFT MAY HELP TO SLOWLY
WEAKEN THE CAPPING INVERSION SHOWN ON MORNING SOUNDINGS.
HOWEVER...MODEL SOLUTIONS SHOW CONSIDERABLE DISPERSION REGARDING
LOCATION AND TIMING OF DEEP CONVECTION. FORECAST SOUNDINGS FROM
NORTHEAST TX INTO WESTERN MS SHOW STEEP MID LEVEL LAPSE
RATES...MODERATE CAPE VALUES...AND SUFFICIENT LOW LEVEL/DEEP LAYER
VERTICAL SHEAR FOR A RISK OF SUPERCELL STRUCTURES IN ANY STORMS THAT
CAN FORM. HAIL/DAMAGING WINDS WOULD BE THE MAIN THREAT...ALTHOUGH
ISOLATED TORNADOES WOULD ALSO BE A CONCERN.

...SOUTH FL...
STRENGTHENING SEA BREEZE CIRCULATIONS WILL AUGMENT LOW-LEVEL ASCENT
INVOF A DIFFUSE SFC FRONT THAT WILL GRADUALLY ADVANCE NWD THROUGH
THE DAY. INSOLATION/DIABATIC HEATING -- LIMITED TO SOME EXTENT BY
MULTI-LAYERED CLOUDINESS STREAMING EWD FROM THE GULF -- WILL SUPPORT
MODEST BOUNDARY-LAYER DESTABILIZATION AS LOWER/MIDDLE 60S DEWPOINTS
SPREAD NWD.

ISOLATED TO SCATTERED PRIMARILY LOW-TOPPED CONVECTION MAY DEVELOP IN
RESPONSE TO THE DIURNALLY STRENGTHENING LOW-LEVEL ASCENT...AND WEAK
MID-LEVEL ASCENT PRECEDING A WEAK SHORTWAVE IMPULSE OVER THE MIDDLE
GULF. MODEST DIRECTIONAL SHEAR IN THE LOW LEVELS COULD SUPPORT A
WEAKLY ROTATING UPDRAFT OR TWO. HOWEVER...ASIDE FROM WEAK LOW-LEVEL
WAA/ISENTROPIC ASCENT...DEEP FORCING FOR ASCENT WILL BE
LACKING...WHILE MID-LEVEL HEIGHT RISES/WARMING OFFSET THE POTENTIAL
FOR DEEP CONVECTION. AS SUCH...CONVECTION SHOULD STRUGGLE TO DEEPEN
SUFFICIENTLY INTO ICING LAYERS ALOFT TO SUPPORT ANY MORE THAN AN
ISOLATED THUNDERSTORM OR TWO. FURTHERMORE...THE LACK OF DEEPER
CONVECTION WILL LIKELY PREVENT STORMS FROM INTERACTING WITH THE
STRONGER MID-LEVEL FLOW...PRECLUDING A THREAT FOR DEEPER/ORGANIZED
CONVECTIVE STRUCTURES.

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