SWODY2
SPC AC 090557
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT MON MAY 09 2011
VALID 101200Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE OH VLY TO THE SE
ATLANTIC COAST...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE NRN
PLAINS/UPPER MS VLY...
...THERE IS A SLGT RISK OF SVR TSTMS IN THE SRN PLAINS...
...MIDWEST TO THE SE ATLANTIC COAST...
MODELS HAVE BEEN MAINTAINING A CONSISTENT MESSAGE IN MAINTAINING A
RIDGE-TOPPING... CONVECTIVELY-INDUCED IMPULSE /CURRENT MCS OVER ERN
DAKOTAS/ SEWD INTO THE OH VLY BY 12Z TUE AND INTO THE SRN
APPALACHIANS AND SERN COASTAL STATES DURING TUESDAY PEAK HEATING.
THIS WILL AUGMENT AN ALREADY ENHANCED BELT OF WNW FLOW ALOFT /H5 40+
KTS/. TSTMS WILL READILY FORM ALONG FRINGE OF THE EML/FRONT AS
HEATING AND LARGE-SCALE SUPPORT SPREADS SEWD TUESDAY AFTN WITH
THREATS FOR ORGANIZED MULTICELL STORMS AND ISOLD SUPERCELLS. DMGG
WIND GUSTS...LARGE HAIL AND POSSIBLY A COUPLE TORNADOES CAN BE
EXPECTED...PARTICULARLY FROM UPSTATE SC/WRN NC TO THE COASTAL
PLAINS.
...NRN PLAINS/UPPER MS VLY...
STRONG MID-LEVEL WAVE...CURRENTLY ROUNDING BASE OF THE WRN STATES
UPR TROUGH...WILL TRANSLATE INTO THE NRN PLAINS BY TUESDAY AFTN.
ATTENDANT SFC LOW WILL TRAVEL NWD FROM NCNTRL SD AT 12Z TUE TO NERN
ND BY EVENING AND INTO SRN MANITOBA OVERNIGHT. DRYLINE/FRONT WILL
ADVANCE NEWD THROUGH ERN ND AND CNTRL/NRN MN TUESDAY AFTN AND MAY BE
FOCUS FOR A FEW SEVERE TSTMS.
WEDGE OF UPR 50S-MID 60S DEW POINTS WILL ADVECT WNW AHEAD OF THE
FRONT TO THE SFC LOW AND CONTRIBUTE TO MLCAPES OF 1500+ J/KG. VERY
STRONG EML SHOULD DECREASE PROBABILITIES FOR SFC-BASED STORMS WITH
SWD EXTENT ALONG THE SURGING FRONT...BUT AS LARGER-SCALE HEIGHT
FALLS/COOLING TEMPERATURES ALOFT GRAZE ERN ND AND CNTRL/NRN
MN...TSTMS MAY FORM. SUPERCELLULAR WIND PROFILES WILL EXIST WITH
THREATS FOR LARGE HAIL AND POSSIBLY TORNADOES. LOW-CONFIDENCE IN
EXTENT OF CONVECTIVE INITIATION WILL PRECLUDE HIGHER PROBABILITIES
AT THIS TIME. WHAT ACTIVITY DOES FORM WILL BEGIN TO ENCOUNTER
COOLER ELY FLOW OFF LAKE SUPERIOR OVER NERN MN WITH TIME TUESDAY
EVENING AND DECREASE TORNADO THREATS. BUT...SUFFICIENT ELEVATED
INSTABILITY WILL EXIST FOR AT LEAST ISOLD LARGE HAIL AS STORMS
DEVELOP ESE TOWARD PARTS OF WI AND UPPER MI TUESDAY NIGHT.
...ERN PARTS OF CNTRL/SRN PLAINS...
REGION WILL REMAIN IN SUSTAINED SLY LOW-LEVEL FLOW THAT WILL
MAINTAIN RELATIVELY RICH BOUNDARY LAYER MOISTURE /SFC DEW POINTS IN
THE 60S/ THROUGH TUESDAY. THIS MOISTURE WILL BE TOPPED BY A STRONG
EML THAT WILL RESULT IN A STRONG CAP...BUT POTENTIALLY VERY STRONG
INSTABILITY GIVEN 8+ DEG C/KM H5-H7 LAPSE RATES.
SECONDARY MID-LEVEL WAVE...EXPECTED TO BEGIN AN ENE TREK TO THE SRN
ROCKIES BY TUESDAY AFTN...WILL RESULT IN WEAKLY DIFLUENT UPR FLOW
REGIME ACROSS THE DRYLINE DURING THE AFTN/EVE. ALTHOUGH STORM
INITIATION CANNOT BE RULED OUT FROM NRN OK INTO CNTRL/ERN
KS...HIGHER PROBABILITIES WILL EXIST FROM CNTRL/SWRN OK INTO THE ERN
EDWARDS PLATEAU OF TX WHERE HOTTEST BOUNDARY LAYER TEMPERATURES
SHOULD EXIST. WIND PROFILES CONSISTING OF VERTICAL SHEAR OF 45-50
KTS...AND THE MAGNITUDE OF LAPSE RATES WILL YIELD SUPERCELLS WITH
LARGE HAIL AND PERHAPS ISOLD TORNADOES/DMGG WIND GUSTS DURING THE
EVENING. ACTIVITY MAY PERSIST INTO LATE EVENING ACROSS ERN OK TO
CNTRL TX WITH AT LEAST ISOLD LARGE HAIL.
MEANWHILE...WRN FRINGES OF EVENING MOISTURE SURGE MAY IGNITE INTO
TSTMS VERY LATE IN THE PERIOD AS THE UPPER TROUGH EDGES TO THE SRN
HIGH PLAINS. THESE STORMS MAY PRODUCE ISOLD LARGE HAIL FROM THE TX
S PLAINS INTO THE TRANS-PECOS REGION OF SW TX.
..RACY.. 05/09/2011
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