SWODY1
SPC AC 041252
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 AM CDT TUE MAY 04 2010
VALID 041300Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE UPR MS VLY...
...SYNOPSIS...
FAST ZONAL FLOW WILL PREVAIL OVER MOST OF THE NATION THIS
PERIOD...WITH THREE EMBEDDED CIRCULATIONS DOMINATING THE CONVECTIVE
FORECAST. THE FIRST OF THESE...NOW OFF THE SRN BC CST...WILL EVOLVE
INTO AN ELONGATED CLOSED LOW OVER WA/ORE BY 12Z WED...WHILE THE
SECOND...NOW OVER SRN SASKATCHEWAN...CONTINUES ESE INTO NRN MN. THE
THIRD FEATURE...A MORE LOOSELY ORGANIZED TROUGH OVER THE UPR GRT
LKS...WILL TRACK E INTO THE HUDSON VLY...IN TANDEM WITH A WEAKENING
SRN STREAM IMPULSE NOW OVER MS.
AT THE SFC...DEEP LOW/FRONTAL SYSTEM SHOULD REDEVELOP ESE FROM SRN
SASKATCHEWAN. A NEW LOW SHOULD FORM NEAR THE TRIPLE POINT OVER THE
ERN DAKOTAS LATER TODAY...AND TRACK E INTO NRN WI THIS EVE AS
TRAILING COLD FRONT SWEEPS ESE INTO NRN IA. FARTHER E... WEAK
TROUGHING WILL PREVAIL OVER ERN NY/WRN NEW ENGLAND TODAY...BEFORE A
RIDGE BUILDS INTO THE REGION TONIGHT/EARLY WED. OVER THE
SOUTHEAST...FRONT NOW EXTENDING FROM THE FL PANHANDLE TO ERN NC
SHOULD FURTHER WEAKEN AS IT CONTINUES SLOWLY SEWD.
...UPR MS VLY...
A POTENT WIND FIELD /WITH 500 MB SPEEDS UP TO 100 KTS/ AND STRONG
FORCING FOR ASCENT WILL OVERSPREAD THE NRN PLNS/UPR MS VLY LATER
TODAY/TONIGHT AS SASKATCHEWAN SYSTEM ELONGATES ESEWD. THE SFC
FRONTAL SYSTEM SHOULD REMAIN WELL-DEFINED AS AFOREMENTIONED TRIPLE
POINT LOW REACHES N CNTRL WI BY EVE. STRONG LOW LVL WARM SECTOR
FLOW WILL ALLOW WARM SFC AIR TO SURGE ENE INTO IA...SE MN AND MUCH
OF WI. MOISTURE WILL...HOWEVER...REMAIN LIMITED...WITH PW AROUND
.50 TO .75 INCHES AND SFC DEWPOINTS IN THE UPR 40S/LWR 50S F.
SPARSE MOISTURE WILL DIMINISH OVERALL SVR THREAT. BUT COMBINATION
OF STRONG DAYTIME HEATING WITH SUBSTANTIAL LARGE SCALE FORCING FOR
ASCENT SHOULD SUPPORT LATE DAY/EARLY EVE STORM DEVELOPMENT FROM NEAR
THE TRIPLE POINT WSW ALONG THE COLD FRONT INTO NRN IA AS SBCAPE
INCREASES TO AOA 500 J/KG. WITH VERTICAL SHEAR /BOTH IN THE LOW
LVLS AND THROUGH THE CLOUD LAYER/ STEADILY STRENGTHENING INTO THE
EVE...SETUP COULD YIELD A BAND OF SUSTAINED STORMS AND EVEN A FEW
EMBEDDED SUPERCELLS. THESE WILL POSE A THREAT FOR DMGG WIND AND SVR
HAIL...DESPITE INCREASING CINH...WELL INTO THE EVE.
...FL PANHANDLE TO S ATLANTIC CST...
A BAND OF DEEP CONVECTION/EMBEDDED TSTMS WILL PERSIST ALONG
WEAKENING FRONTAL ZONE OVER THE FL PANHANDLE/GA AND THE ERN
CAROLINAS TODAY...FED BY LINGERING AXIS OF VERY RICH MOISTURE /PW
AROUND 2 INCHES/ OVER THE NERN GULF. WIND PROFILES OVER THE REGION
ATTM /PER TLH 12Z RAOB AND AREA VWP DATA/ ARE FAVORABLE FOR LOW LVL
STORM ROTATION...GIVEN A VERY MOIST BOUNDARY LAYER ...THE PRESENCE
OF DISCRETE OR SEMI-DISCRETE STORMS...AND SOME DEGREE OF LARGE SCALE
FORCING FOR ASCENT. SATELLITE DATA SUGGEST...HOWEVER...THAT FORCING
FOR ASCENT...AND WINDS...WILL DECREASE AS MS IMPULSE SHEARS RAPIDLY
NEWD TODAY. IN ADDITION...CURRENT RADAR LOOP SHOWS A LARGELY LINEAR
STORM MODE OVER THE REGION. SFC HEATING COULD ALLOW A WINDOW OF
OPPORTUNITY FOR MORE DISCRETE STORM DEVELOPMENT...AND A
CORRESPONDING INCREASE IN THE POTENTIAL FOR A TORNADO OR TWO FROM
THE FL PANHANDLE ENE TO THE SC/NC CST...BEFORE THE WIND FIELD
DIMINISHES LATER TODAY. BUT OVERALL SETUP SUGGESTS THAT ANY SUCH
THREAT SHOULD REMAIN ISOLATED.
...UPSTATE NY/NEW ENGLAND...
LOW TO MID LVL LAPSE RATES AND FORCING FOR ASCENT WILL INCREASE OVER
NY/MUCH OF NEW ENGLAND TODAY AS UPSTREAM UPR TROUGH MOVES ACROSS
REGION AND ASSUMES A NEGATIVE TILT. THIS SHOULD LEAD TO THE
DEVELOPMENT OF SCTD TSTMS BY LATE MORNING...WITH ACTIVITY TENDING TO
EVOLVE INTO CLUSTERS/BKN LINES NEAR AFOREMENTIONED SFC TROUGH. COOL
MID LVL TEMPERATURES /AROUND MINUS 20 C AT 500 MB/ AND
UNIDIRECTIONAL WIND PROFILES LIKELY WILL SUPPORT HAIL AND GUSTY SFC
WINDS. BUT RELATIVELY LIMITED MOISTURE /PW UP TO .75 INCHES WITH
SFC DEWPOINTS IN THE UPR 40S F/ SHOULD MITIGATE COVERAGE/INTENSITY
OF ASSOCIATED SVR THREAT.
..CORFIDI/GARNER.. 05/04/2010
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