This doesn't happen every day

We don't get dynamics like this all of the time in St. Louis. SPC has had us pegged in a moderate risk bubble since Sunday. We had a pretty good batch of hail around 4:00 this morning from an elevated storm, which even my 4:00 am still sleeping brain took as a sign of impressive instability.

I'm especially interested to see if we get any supercells forming out in front of the main frontal squall line.

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1112 AM CDT WED MAY 13 2009

VALID 131630Z - 141200Z

...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER PARTS OF OK...SOUTHEAST KS...NORTHWEST AR...MUCH OF MO AND MUCH OF IL...

...SYNOPSIS...
VIGOROUS TROUGH AND STRONG POLAR JET MAX MOVES EWD FROM NRN PLAINS TO UPPER GREAT LAKES LATER TONIGHT...WITH GREATEST CONVECTIVE POTENTIAL REMAINING ALONG THE SRN PERIPHERY OF THIS SYSTEM WHERE THE RESERVOIR OF MOIST/UNSTABLE AIR MASS RESIDES. COLD FRONT EXTENDS FROM THE DEEP LOW WRN ONTARIO SWWD THRU UPPER MS VALLEY...CENTRAL KS TO NRN TX PANHANDLE THIS AM.

VERY STRONG SWLY LOW LEVEL JET AOA 60KT FROM SRN PLAINS INTO LOWER MO VALLEY CHARACTERIZED BY A PRONOUNCED EML ATOP A VERY MOIST BUT RELATIVELY SHALLOW MOIST LAYER. STRONG ISENTROPIC ASCENT UNDERWAY ACROSS MID MS VALLEY WITH CURRENT ELEVATED THUNDERSTORMS EXPECTED TO CONTINUE AND LIKELY BECOME MORE INTENSE THRU THE AFTERNOON.

...MID MS VALLEY/LOWER MO VALLEY...
PERSISTENT ELEVATED THUNDERSTORMS MID MS INTO LOWER OH VALLEYS WILL TRANSITION INTO A MORE SURFACE BASED SUPERCELL THREAT BY MID AFTERNOON AS TEMPERATURES CLIMB ALONG WITH DEWPOINTS TO THE S AND W ACROSS MO INTO SERN KS. WITH MID LEVEL LAPSE RATES IN EXCESS OF 8C/KM AND DEWPOINTS RISING THRU THE 60S F...MLCAPES UPWARD OF 2500
J/KG WILL DEVELOP WITH WEAKENING CINH BY MID AFTERNOON UPSTREAM FROM THE ONGOING ELEVATED STORMS. WHILE DEEP LAYER SHEAR OF 40KT IS NOT PARTICULARLY STRONG FOR TORNADIC SUPERCELLS...THE ENHANCED LOW LEVEL SHEAR VICINITY OF CONVECTIVE BOUNDARIES WILL LOCALLY ENLARGE HODOGRAPHS AND BE QUITE FAVORABLE FOR AT LEAST A COUPLE SUPERCELLS CAPABLE OF PRODUCING STRONG TORNADOES BY LATER THIS AFTERNOON/EVENING GIVEN THE EXPECTED INSTABILITY. IN ADDITION VERY LARGE HAIL SHOULD OCCUR WITH ANY SUPERCELL AND WIND DAMAGE WILL BECOME MORE OF A THREAT AS CONVECTION TRANSITIONS INTO MORE OF A LINEAR MODE BY THIS EVENING.

ANOTHER FACTOR IN TODAYS CONVECTIVE SCENARIO WILL LIKELY BY THE MCV NOW INTO SWRN MO. AS AIR MASS DESTABILIZES ACROSS SRN MO IN ADVANCE OF THIS FEATURE A SEVERE THUNDERSTORM THREAT WOULD LIKELY DEVELOP BY MID AFTERNOON.