DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 191619
SWODY1
SPC AC 191617

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1117 AM CDT SAT MAY 19 2012

VALID 191630Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CENTRAL/SRN
PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER SOUTH FL...

...CENTRAL/SRN PLAINS...
UPPER TROUGH OVER CO IS MOVING EWD TOWARD THE CENTRAL PLAINS AND
MODEL GUIDANCE INDICATES THIS FEATURE WILL BEGIN TO LIFT ENEWD
REACHING THE MIDDLE MO RIVER VALLEY LATER TONIGHT. THE TROUGH IS
ASSOCIATED WITH COLD MID LEVEL TEMPERATURES /-17C AT 500 MB/ WHICH
WILL SPREAD EWD INTO THE PLAINS THIS AFTERNOON AND EVENING. PRIMARY
SURFACE COLD FRONT EXTENDS FROM NWRN MN SSWWD ACROSS CENTRAL
NEB...WRN KS INTO THE NWRN TX PANHANDLE. THE FRONT WILL PROGRESS EWD
REACHING ERN NEB/CENTRAL KS/NWRN OK LATE THIS AFTERNOON/EVENING AND
PROVIDE A FOCUS FOR THUNDERSTORM DEVELOPMENT.

ALTHOUGH STRONG SOUTHERLY LOW LEVEL WINDS ARE CONTINUING FROM THE
SRN PLAINS INTO THE UPPER MS VALLEY...LOW LEVEL MOISTURE WILL BE
SLOW TO INCREASE SUBSTANTIALLY OWING TO PERSISTENT ANTICYCLONIC
TRAJECTORIES ACROSS THE WRN GULF OF MEXICO AND THE TX COAST. THIS
WILL LIMIT WARM SECTOR SURFACE DEW POINTS TO AROUND 60F OVER NEB AND
KS. HOWEVER...THE PRESENCE OF STEEP MID LEVEL LAPSE RATES
ASSOCIATED WITH AN ELEVATED MIXED LAYER OVER THE PLAINS WILL ENHANCE
POTENTIAL INSTABILITY WITH CAPE VALUES REACHING 1500-2000 J/KG LATER
THIS AFTERNOON AND EVENING. THE EML IS ALSO EXPECTED TO INHIBIT
DEVELOPMENT OF SURFACE-BASED STORMS UNTIL MID/LATE AFTERNOON ALONG
THE FRONT WHEN DIABATIC HEATING AND FOCUSED UPWARD MOTION WEAKEN THE
CAP SUFFICIENTLY FOR STORMS TO DEVELOP. CONSENSUS OF TRADITIONAL
AND CONVECTION-ALLOWING MODEL GUIDANCE PREDICTS CONVECTIVE
INITIATION FROM SOUTH CENTRAL NEB ACROSS CENTRAL KS INTO NWRN OK
DURING THE 21-23Z TIME FRAME.

AS THE UPPER TROUGH MOVES EWD...40-50 KT MID LEVEL SWLY FLOW WILL
OVERSPREAD THE FRONTAL REGION PROVIDING SUFFICIENT DEEP LAYER SHEAR
TO ENHANCE CONVECTIVE ORGANIZATION AND INTENSITY...INCLUDING
SUPERCELL STRUCTURES. THE STEEP LAPSE RATES WILL PROMOTE A THREAT
FOR VERY LARGE HAIL WITH STRONGER CELLS...WHILE THE WELL MIXED
BOUNDARY LAYER WILL ALSO FAVOR POTENTIAL FOR DAMAGING WIND GUSTS.
WITHIN SEVERAL HOURS AFTER INITIATION...THE STORMS ARE EXPECTED TO
DEVELOP INTO ONE OR MORE CONVECTIVE BANDS/LINES WITH ACTIVITY THEN
SPREADING EWD/NEWD WITH A GRADUAL TRANSITION INTO PRIMARILY A WIND
DAMAGE THREAT WITH TIME. ACTIVITY IS EXPECTED TO SLOWLY WEAKEN
AFTER 03Z AS DIURNAL STABILIZATION OCCURS AFTER SUNSET.

...SOUTH FL...
THE SYNOPTIC PATTERN AND THERMODYNAMIC ENVIRONMENT APPEAR SIMILAR TO
YESTERDAY WITH 12Z MFL SOUNDING SHOWING -10C AT 500 MB WITH
RESULTANT STEEPER LAPSE RATES ENHANCING INSTABILITY. ALTHOUGH LOW
LEVEL WINDS BELOW 700 MB REMAIN WEAK...A STRONG SUBTROPICAL JET IS
POSITIONED OVER SOUTH FL WITH 100 KT AT 200 MB. STRONG HEATING
NORTH OF THE CLOUD COVER OVER EXTREME SRN FL WILL PERMIT STORMS TO
DEVELOP WITHIN THE WEAKLY CAPPED ENVIRONMENT DURING THE EARLY/MID
AFTERNOON...WITH POTENTIAL FOR STRONGER CELLS TO PRODUCE LOCALIZED
DAMAGING WET MICROBURSTS AND MARGINALLY SEVERE HAIL.

...TN VLY/N GA AREA...
WRN EXTENSION OF LONG-LIVED...CAROLINAS UPPER TROUGH WILL MAINTAIN
CORRIDOR OF COOL MID LVL TEMPS /AOB -14 C AT 500 MB/ ATOP
STRONGLY-HEATED...RELATIVELY MOIST...VERY WEAKLY SHEARED ENVIRONMENT
OVER PARTS OF TN AND THE WRN SLOPES OF THE SRN APPALACHIANS. THIS
SETUP MAY YIELD DIURNAL PULSE STORMS WITH ISOLATED WET MICROBURSTS
AND/OR SVR HAIL.

..WEISS/GARNER.. 05/19/2012

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