DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 150541
SWODY1
SPC AC 150539

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1239 AM CDT TUE MAY 15 2012

VALID 151200Z - 161200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER MS
VALLEY AND WRN GREAT LAKES REGION...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE
CAROLINAS...

...UPPER MS VALLEY/WRN GREAT LAKES REGION...
AN UPPER-LEVEL TROUGH WILL MOVE SEWD FROM ONTARIO INTO THE WRN GREAT
LAKES REGION TODAY. AT THE SFC...A COLD FRONT WILL ADVANCE SEWD
ACROSS WI AND NRN LOWER MI WITH DEWPOINTS AHEAD OF THE BOUNDARY IN
THE UPPER 40S AND LOWER 50S F. WARMING SFC TEMPS BY EARLY AFTERNOON
SHOULD YIELD SBCAPE VALUES OF 1000 TO 1500 J/KG FROM ERN IA NEWD TO
AROUND MILWAUKEE. AS THE INSTABILITY AXIS TAKES SHAPE AND LOW-LEVEL
CONVERGENCE INCREASES...THE MODELS DEVELOP THUNDERSTORMS DURING THE
LATE AFTERNOON...MOVING THE CONVECTION SEWD ACROSS THE SLIGHT RISK
AREA.

FORECAST SOUNDINGS AT MILWAUKEE WI AND DAVENPORT IA AROUND 21Z SHOW
30 TO 40 KT OF 0-6 KM SHEAR WITH MID-LEVEL LAPSE RATES OF 8.0 T 8.5
C/KM. THIS ENVIRONMENT SHOULD SUPPORT SUPERCELLS AND/OR SEVERE
MULTICELL LINE SEGMENTS AS STORMS LINE UP ALONG THE FRONT. ISOLATED
LARGE HAIL AND WIND DAMAGE WILL BE POSSIBLE DURING THE LATE
AFTERNOON AND EARLY EVENING WHEN INSTABILITY IS FORECAST TO BE
STRONGEST. DUE TO THE RELATIVELY DRY BOUNDARY LAYER...THE THREAT
SHOULD DIMINISH QUICKLY AFTER DARK AS INSTABILITY DECREASES ACROSS
THE REGION.

...ERN SEABOARD/SRN AND CNTRL APPALACHIAN FOOTHILLS...
SOUTHWEST FLOW WILL REMAIN IN PLACE ACROSS THE ERN STATES TODAY WITH
A BROAD WARM SECTOR LOCATED FROM THE CNTRL GULF COAST STATES NEWD
INTO THE MID-ATLANTIC REGION. SCATTERED THUNDERSTORMS ARE FORECAST
TO DEVELOP ALONG THE CORRIDOR OF MODERATE INSTABILITY DURING THE
EARLY TO MID AFTERNOON. MODEL CONSENSUS PLACES THE GREATEST
CONVECTIVE COVERAGE FROM NCNTRL NC SWWD INTO ERN GA WHERE MLCAPE
VALUES SHOULD REACH THE 2000 TO 2500 J/KG RANGE. IN
ADDITION...FORECAST SOUNDINGS AT 21Z THIS AFTERNOON IN COLUMBIA SC
AND RALEIGH NC SHOW 25 TO 35 KT OF 0-6 KM SHEAR WITH STEEP LOW-LEVEL
LAPSE RATES. THIS ENVIRONMENT SHOULD SUPPORT A WIND DAMAGE THREAT
ESPECIALLY WITH LINE SEGMENTS THAT CAN ORGANIZE AND PERSIST DURING
THE LATE AFTERNOON. ISOLATED LARGE HAIL WILL ALSO BE POSSIBLE IN
AREAS WHERE STORMS HAVE ACCESS TO STRONG INSTABILITY. HAVE ADDED A
SLIGHT RISK ACROSS CNTRL NC AND SC WHERE CONFIDENCE IS GREATEST
CONCERNING THE POTENTIAL FOR SEVERE STORMS.

...SOUTH TX...
A POSITIVELY-TILTED UPPER-LEVEL TROUGH WILL MOVE SEWD ACROSS THE SRN
PLAINS TODAY. ALONG AND AHEAD OF THE TROUGH AXIS...THE MODELS
DEVELOP WEAK INSTABILITY FROM THE TX HILL COUNTRY SWD INTO SOUTH TX
WITH INCREASING DEEP LAYER SHEAR WITH SWD EXTENT. FORECAST SOUNDINGS
AT BROWNSVILLE THIS AFTERNOON SHOW 0-6 KM SHEAR OF 45 TO 50 KT WHICH
SHOULD BE ENOUGH FOR A SEVERE THREAT. HOWEVER...MLCAPE VALUES ARE
ONLY FORECAST TO BE IN THE 500 TO 750 J/KG RANGE SUGGESTING ANY
SEVERE THREAT WILL REMAIN MARGINAL. THE STRONGER CELLS COULD HAVE A
THREAT FOR HAIL AND STRONG WIND GUSTS.

..BROYLES/COHEN.. 05/15/2012

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