DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 151958
SWODY1
SPC AC 151955

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0255 PM CDT THU AUG 15 2013

VALID 152000Z - 161200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CENTRAL AND
SOUTHERN PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER SOUTHEAST GA AND NORTHEAST
FL...

...CENTRAL AND SRN PLAINS...
OBJECTIVE ANALYSES INDICATED THE ENVIRONMENT ACROSS MORE OF CENTRAL
KS INTO CENTRAL OK AND SOUTHWARD INTO THE LOW ROLLING PLAINS OF
NORTHWEST TX HAS BECOME MODERATELY UNSTABLE THIS AFTERNOON.
SATELLITE AND RADAR IMAGERY SHOWED TSTMS DEVELOPING WITHIN A
CORRIDOR OF LOW LEVEL CONVERGENCE EXTENDING FROM S-SE OF KABI NNEWD
THROUGH WRN NORTH TX...WEST CENTRAL OK INTO CENTRAL KS. THE
COMBINATION OF THE INSTABILITY AND EFFECTIVE BULK SHEAR OF 25-35 KT
SUGGESTS THE SEVERE WEATHER THREAT HAS EXPANDED EWD SOME AND THUS
RESULTS IN THE EWD SPATIAL CHANGE TO THE SLIGHT RISK AREA.

ADDITIONAL STORMS SHOULD CONTINUE TO DEVELOP IN VICINITY OF A SWD
MOVING OUTFLOW BOUNDARY IN NWRN...CENTRAL AND NORTH CENTRAL
KS...WITH THE LATTER AREA HAVING STORMS FORM AT THE MERGER OF TWO
OUTFLOW BOUNDARIES. WHILE A SLIGHT RISK REMAINS INTO PART OF SRN
NEB...THE HIGHER SEVERE WIND/HAIL PROBABILITIES /I.E. 30 PERCENT
RISK LEVEL/ ARE NOT EXPECTED TO EXTEND TO THE NEB BORDER WITH THE
NRN EXTENT NOW AS FAR NORTH AS THE NWRN-NORTH CENTRAL KS OUTFLOW
BOUNDARY.

...SRN GA/NRN FL...
TSTM/SVR WEATHER THREAT FORECAST REMAINS ON TRACK ACROSS THE PORTION
OF THE SOUTHEAST STATES...WITH OBJECTIVE ANALYSES INDICATING THE
ENVIRONMENT HAS BECOME MODERATELY UNSTABLE. FOR ADDITIONAL
MESOSCALE DETAILS FOR THIS REGION...PLEASE REFER TO SPC MESOSCALE
DISCUSSION 1721.

..PETERS.. 08/15/2013

.PREV DISCUSSION... /ISSUED 1138 AM CDT THU AUG 15 2013/

CORRECTED TO REMOVE EXTRA GENL TSTM LINE OVER MAINE.

...WRN TO CNTRL KS SOUTH TO TX/OK PNHDLS AND WRN OK...
MID-LEVEL TROUGHING AND STRENGTHENING NNWLY MID-LEVEL FLOW IS
FORECAST OVER THE GREAT PLAINS THROUGH TONIGHT DOWNSTREAM FROM
MID/UPPER RIDGE AMPLIFICATION ACROSS THE ROCKIES. THIS PROCESS WILL
CONTRIBUTE TO A WEAK LEE CYCLONE RIPPLING SSEWD ALONG/NEAR
SFC/THERMAL TROUGH AXIS FROM ERN CO TO TX PNHDL BY FRIDAY MORNING.

MORNING WATER VAPOR AND VISIBLE SATELLITE LOOPS DEPICT AT LEAST TWO
SHORTWAVE TROUGHS THAT WILL ACT TO ENHANCE ASCENT ACROSS KS THROUGH
THE AFTERNOON AND INTO THE EVENING. THE FIRST...A MCV ASSOCIATED
WITH LOOSELY ORGANIZED OVERNIGHT MCS...WAS MOVING INTO NRN KS LATE
THIS MORNING. THE OUTFLOW BOUNDARY FROM THE MCS EXTENDED FROM
E-CNTRL KS WWD/NWWD TO NERN CO. NEW ELEVATED CONVECTION WAS
OCCURRING AMIDST AN EXPANDING ACCAS FIELD WELL AHEAD OF THE MCV AND
OUTFLOW FROM CNTRL KS TO WRN/CNTRL OK. WEAK POST-OUTFLOW CONVECTION
WAS PERSISTING OVER NERN CO AND SRN NEB.
THE SECOND SHORTWAVE TROUGH WAS EVIDENT ACROSS MT/WY. THIS IMPULSE
WILL LIKELY ACT TO REINFORCE OR SUSTAIN DEEP-LAYER ASCENT AND
STRENGTHENING SHEAR ACROSS THE PLAINS THROUGH TONIGHT.

HEATING/MIXING WILL ELIMINATE WEAK CONVECTIVE INHIBITION ACROSS THE
RISK AREA THROUGH THE AFTERNOON WITH SFC-BASED STORMS LIKELY BY LATE
AFTERNOON. LOW 60S F BOUNDARY LAYER DEWPOINTS BENEATH 7-8 C/KM
MID-LEVEL LAPSE RATES WILL RESULT IN MLCAPE OF 2000-2500 J/KG.
DEEP-LAYER VERTICAL SHEAR WILL BE FAVORABLE FOR SUPERCELLS GIVEN
30-50 KT NNWLY FLOW ALOFT AND WEAK SLY/SWLY LOW-LEVEL FLOW.
INITIALLY...THE POTENTIAL FOR DISCRETE SUPERCELLS WILL EXIST AND
THESE STORMS WILL BE CAPABLE OF PRODUCING VERY LARGE HAIL AND STRONG
TO DAMAGING WINDS. HODOGRAPH CURVATURE AND BOUNDARY LAYER RH ARE
LIMITED BY LACK OF STRONGER LOW LEVEL FLOW AND MOISTURE RESPECTIVELY
AND THESE FACTORS MAY LIMIT TORNADO POTENTIAL. HOWEVER...IF
CONVECTION CAN REMAIN AT LEAST SEMI-DISCRETE INTO THE EARLY
EVENING...THE POSSIBILITY OF STORM/BOUNDARY INTERACTIONS AND A
SLIGHT INCREASE IN LOW LEVEL FLOW COULD ENHANCE THE CHANCE FOR A
TORNADO OR TWO. IN ADDITION TO INITIAL RISK FOR DAMAGING SUPERCELL
GUSTS...SOME CHANCE EXISTS FOR UPSCALE/MCS ORGANIZATION OVERNIGHT.
LATEST STORM SCALE GUIDANCE SUGGESTS THIS POTENTIAL WILL REMAIN
QUITE LIMITED AND PROBABLY FOCUSED FROM SRN KS TO NRN OK DURING THE
LATE EVENING/OVERNIGHT HOURS.

...NRN FL/SRN GA...
A QUASI-STATIONARY FRONT FROM WRN FL PNHDL ACROSS SRN GA HAS BECOME
BETTER DEFINED THIS MORNING DUE TO DENSE CLOUD COVER TO THE NORTH
AND RESULTANT DIFFERENTIAL HEATING. MLCAPE ALONG AND SOUTH OF THE
BOUNDARY HAS ALREADY CLIMBED TO AROUND 2000 J/KG AHEAD OF A CLUSTER
OF ROBUST CONVECTION SPREADING ENEWD FROM FL PNHDL/SWRN GA. A WEAK
MID-LEVEL IMPULSE ROTATING THROUGH THE BASE OF THE LARGER SCALE
TROUGH...AND MODEST 25KT MID-LEVEL FLOW...SHOULD CONTRIBUTE TO STORM
ORGANIZATION/PERSISTENCE AND ACT TO ENHANCE LIFT ALONG THE FRONTAL
ZONE THROUGH THE AFTERNOON. ADDITIONAL CONVECTION WILL LIKELY
INCREASE ALONG SEA BREEZES ACROSS FL. GIVEN CURRENT TRENDS...A
CORRIDOR WITH A GREATER DOWNBURST WIND POTENTIAL MAY EVOLVE OVER
PORTIONS OF NRN FL AND SRN GA INTO THE AFTERNOON. THUS...TSTM WIND
PROBABILITIES HAVE BEEN INCREASED ACROSS THESE AREAS.

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