SWODY2
SPC AC 121730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT WED SEP 12 2007
VALID 131200Z - 141200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
UPPER TROUGH NOW MOVING THROUGH SRN BRITISH COLUMBIA WILL AMPLIFY
SEWD INTO THE UPPER MS VALLEY AND GREAT LAKES BY LATE THURSDAY
AFTERNOON AND EVENING. INITIAL VORT MAX WILL EJECT NE THROUGH BASE
OF UPPER TROUGH AND INTO SWRN ONTARIO EARLY IN THE DAY...WHILE
SECONDARY IMPULSE ADVANCES SEWD THROUGH THE UPPER MS VALLEY DURING
THE AFTERNOON. SURFACE LOW WILL SHIFT NEWD INTO SWRN ONTARIO IN
ASSOCIATION WITH LEAD IMPULSE...WHILE TRAILING COLD FRONT ADVANCES
SEWD THROUGH UPPER MS VALLEY AND GREAT LAKES. SWRN EXTENTION OF
FRONT WILL MOVE SWD THROUGH THE CNTRL PLAINS THURSDAY AND INTO THE
SRN PLAINS THURSDAY NIGHT.
TROPICAL DEPRESSION OVER THE NWRN GULF IS FORECAST TO MOVE NWD
BEFORE GRADUALLY TURNING MORE NEWD INTO THE SWRN GULF COASTAL
STATES. SEE THE LATEST GUIDANCE FROM NHC FOR FURTHER DETAILS.
..WI AND IA...
RICHER LOW LEVEL MOISTURE WITH 65-70F DEWPOINTS IS CONFINED TO THE
GULF COASTAL REGION WITH MID TO UPPER 50S DEWPOINTS FARTHER NWD INTO
OK AND AR. STRENGTHENING SLY LOW LEVEL JET ASSOCIATED WITH
DEVELOPING CYCLONE OVER THE NRN PLAINS WILL RESULT IN ADVECTION OF
MODIFIED CP AIR NWD INTO THE UPPER MS VALLEY AND GREAT LAKES AREA BY
THURSDAY AFTERNOON. MID 50S DEWPOINTS WILL BE POSSIBLE AS FAR NORTH
AS IA AND WI BY LATE DAY THURSDAY. STEEPER LAPSE RATES WILL SPREAD
EWD OVER THE MODEST MOIST AXIS AND RESULT IN POTENTIAL FOR MARGINAL
INSTABILITY AND A CAPPING INVERSION BY AFTERNOON. SWLY FLOW IN THE
850-500 MB LAYER WILL STRENGTHEN WITH APPROACH OF THE UPPER TROUGH.
DEEP LAYER VERTICAL WIND PROFILES WILL BECOME FAVORABLE FOR
ORGANIZED STORMS. STORMS WILL LIKELY DEVELOP FROM PARTS OF WI SWWD
THROUGH IA LATE AFTERNOON WHERE DEEP ASCENT WITHIN FRONTAL ZONE
SHOULD WEAKEN CAP SUFFICIENTLY FOR INITIATION. POTENTIAL WILL EXIST
FOR HAIL AND STRONG TO DAMAGING WIND GUSTS AS ACTIVITY MOVES EWD
THROUGH EARLY EVENING. MAIN LIMITING FACTOR IS LIKELIHOOD OF VERY
MARGINAL INSTABILITY...THEREFORE WILL INTRODUCE ONLY 5% SEVERE
PROBABILITIES AT THIS TIME. HOWEVER...AREA WILL CONTINUE TO BE
EVALUATED FOR A POSSIBLE UPGRADE TO SLIGHT RISK.
..CNTRL PLAINS REGION...
LOW LEVEL DEWPOINTS IN THE UPPER 50S TO AROUND 60 BENEATH PLUME OF
STEEPER LAPSE RATES WILL LIKELY RESULT IN STRONGER INSTABILITY THAN
FARTHER NORTH WITH MLCAPE AROUND 1500 J/KG POSSIBLE FROM THE TX
PANHANDLE INTO PARTS OF KS. HOWEVER...THIS REGION WILL BE S OF THE
STRONGER FLOW ALOFT...AND PHASING BETWEEN SHORTWAVE TROUGH NOW OVER
SRN CO AND SWD MOVING FRONTAL BOUNDARY WILL NOT BE FAVORABLY TIMED.
THIS LEAVES UNCERTAINTY REGARDING DEGREE OF THUNDERSTORM COVERAGE IN
THIS AREA. NEVERTHELESS...A FEW MULTICELL STORMS WILL BE POSSIBLE AS
THE FRONT ADVANCES THROUGH KS DURING PEAK HEATING. THREAT WILL EXIST
FOR ISOLATED HAIL AND STRONG WIND GUSTS.
..LS AND MS...
THREAT FOR AN ISOLATED TORNADO OR TWO OR STRONG WIND GUSTS WILL
EXIST OVER PARTS OF LA AND MS AS STRONGER BOUNDARY LAYER WINDS
ATTENDING THE TROPICAL DEPRESSION MOVE INLAND AND INTERACT WITH
BAROCLINIC ZONE NEAR THE GULF COAST.
.DIAL.. 09/12/2007
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