Mesoscale Discussion 772

MESOSCALE DISCUSSION 0772
NWS STORM PREDICTION CENTER NORMAN OK
1105 AM CDT FRI MAY 02 2008
AREAS AFFECTED...CNTRL AND ERN IA THROUGH EXTREME SERN MN AND SWRN
WI
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 021605Z - 021800Z
STORMS ARE EXPECTED TO DEVELOP AND INTENSIFY ACROSS ERN IA...SERN MN
AND SRN WI THIS AFTERNOON. SUPERCELLS CAPABLE OF PRODUCING LARGE
HAIL AND ISOLATED TORNADOES WILL BE THE MAIN THREATS. WW WILL LIKELY
BE NEEDED ONCE IT BECOME APPARENT THAT SURFACE BASED INITIATION IS
IMMINENT.
LATE THIS MORNING A WARM FRONT EXTENDS FROM A SURFACE LOW IN SW IA
NEWD THROUGH NE IA THEN EAST THROUGH SRN WI. COLD FRONT EXTENDS SWD
FROM THE LOW THROUGH THE MID MS VALLEY. OCCLUDED FRONT EXTENDS NWWD
FROM THE LOW THROUGH WRN IA AND SERN SD. WARM SECTOR OVER ERN IA IS
DESTABILIZING WITH TEMPERATURES WARMING INTO THE LOW TO MID 60S AND
BOUNDARY LAYER DEWPOINTS IN THE UPPER 50S. THE 12Z RAOB DATA FROM
DAVENPORT ALSO DEPICTED 7.7 C/KM 700-500 MB LAPSE RATES...AND MLCAPE
FROM 1000 TO 1500 J/KG IS LIKELY IN THIS REGION THIS AFTERNOON.
WV IMAGERY SHOWS AN UPPER VORT MAX LIFTING NWD ALONG ERN PERIPHERY
OF UPPER TROUGH AND INTO THE MID-UPPER MS VALLEY REGION. SCATTERED
THUNDERSTORMS CONTINUE DEVELOPING IN ASSOCIATION WITH THIS FEATURE
IN AN ARC FROM ERN NEB THROUGH SWRN IA. ACTIVITY SO FAR HAS BEEN
SLIGHTLY ELEVATED AND DEVELOPING WITHIN ZONE OF ASCENT ALONG A LOW
LEVEL STRATUS DECK. AS THE BOUNDARY LAYER CONTINUES TO DESTABILIZE
DOWNSTREAM ACROSS ERN IA...ADDITIONAL STORMS WILL LIKELY DEVELOP AND
BECOME SURFACE BASED. AS THE LOW LEVEL JET LIFTS NWWD INTO THE OH
VALLEY AND GREAT LAKES...SWLY 850 MB WINDS SHOULD INCREASE OVER ERN
IA AND SRN WI WITH SELY LOW FLOW LIKELY MAINTAINED EAST OF SURFACE
LOW. THIS WILL RESULT IN FAVORABLE 0-1 KM HODOGRAPHS FOR SUPERCELLS
WITH LOW LEVEL MESOCYCLONES.
..DIAL.. 05/02/2008