SWODY1
SPC AC 201243
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0743 AM CDT WED MAY 20 2009
VALID 201300Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF CNTRL AND SRN
FL...
...THERE IS A SLGT RISK OF SVR TSTMS OVER A SMALL PART OF THE
CNTRL/NRN PLNS...
...SYNOPSIS...
MAIN BELT OF THE WLYS WILL ONCE AGAIN REMAIN CONFINED TO THE NWRN
STATES...THE NRN PLNS...AND SERN CANADA THIS PERIOD AS ELONGATED
RIDGE EDGES SLOWLY E FROM THE OH VLY TO THE MID ATLANTIC CST.
FARTHER S...ERN GULF OF MEXICO LOW EXPECTED TO REDEVELOP SLIGHTLY
WWD...WHILE A BROAD/WEAK TROUGH WITH SEVERAL EMBEDDED DISTURBANCES
PREVAILS OVER THE SOUTHWEST.
AT LWR LVLS...COLD FRONT NOW IN THE WRN DAKOTAS...ASSOCIATED WITH
SHORTWAVE IMPULSE NOW IN SK/MT...SHOULD MOVE SE INTO NRN NEB/SE SD
BY EVE WHILE LEE TROUGH MIXES E OVER ERN CO/WRN NEB. OVER FL...DEEP
E-W CONFLUENCE AXIS OVER THE CNTRL PART OF THE STATE MAY MOVE A BIT
NWD TODAY...BEFORE REFORMING FARTHER NW TONIGHT/EARLY THURSDAY.
...CNTRL/NRN PLNS...
NEB/SD COLD FRONT AND HI PLNS LEE TROUGH SHOULD BE THE FOCUS FOR
AFTN STORM DEVELOPMENT AND AN ASSOCIATED SVR THREAT LATER
TODAY/EARLY TONIGHT AS SFC HEATING DESTABILIZES REGION. MOISTURE
AVAILABILITY WILL REMAIN MODEST BY MID-MAY STANDARDS. BUT
COMBINATION OF MODERATE CONVERGENCE WITH STEEP LOW- TO MID-LVL LAPSE
RATES SHOULD SUPPORT SCTD STRONG UPDRAFTS. A FEW STORMS ALSO MAY
FORM OVER THE WY MOUNTAINS. WLY FLOW ALOFT AND POST-FRONTAL ELY
FLOW AT THE SFC SHOULD FOSTER EWD PROPAGATION OF THIS ACTIVITY INTO
THE LWR PLNS.
SLY PRE-FRONTAL SFC WINDS BENEATH 25-30 KT WSWLY FLOW AT MID LVLS
SHOULD BE SUFFICIENT FOR SUSTAINED STORMS...AND POSSIBLY A FEW WITH
WEAK MID-LVL ROTATION. COUPLED WITH DEEPLY MIXED ENVIRONMENT...
SETUP MAY YIELD STRONG...EVAPORATIVELY-ENHANCED SFC WINDS AND SVR
HAIL. THE STORMS MAY EVOLVE INTO A SMALL CLUSTER OR TWO THIS EVE.
THESE SHOULD WEAKEN AS THEY MOVE MAINLY E INVOF THE FRONT LATER
TONIGHT. A FEW STRONG ELEVATED STORMS MAY PERSIST IN THE WAKE OF
THE FRONT OVER SRN SD/NRN NEB/SW MN/NW IA THROUGH EARLY THU.
...CNTRL/SRN FL...
SFC HEATING WILL OCCUR OVER S CNTRL FL TODAY...S OF AFOREMENTIONED
DEEP CONFLUENCE AXIS AND BENEATH MID LVL DRY SLOT THAT WILL SPIRAL
WNW ACROSS REGION THROUGH MIDDAY. SATELLITE AND SFC DATA SHOW
SEVERAL LOW LVL BOUNDARIES/CONFLUENCE FEATURES THAT SHOULD SERVE TO
FOCUS CONVECTIVE DEVELOPMENT LATER THIS MORNING. GIVEN COOL MID LVL
TEMPERATURES /BLO MINUS 10 C AT 500 MB/ AND SFC DEWPOINTS IN THE UPR
60S F...SETUP MAY SUPPORT A FEW STORMS WITH SVR HAIL. IN
ADDITION...MODERATE LOW-LVL VEERING PROFILES OVER THE E CNTRL PART
OF THE STATE WILL ENHANCE THE LIKELIHOOD FOR LOW LVL ROTATION
...GIVEN A SUSTAINED STORM. THUS...A CONDITIONAL THREAT WILL EXIST
FOR ISOLD TORNADOES. THE SVR THREAT SHOULD DIMINISH ONCE STORMS
BEGIN TO DESTRUCTIVELY INTERFERE LATER TODAY.
..CORFIDI/JEWELL.. 05/20/2009
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