A small popcorn style thunderstorm forms and stayed over Marengo. The storm gave us some nickle sized hail and a decent lightning show before fading away about 20minutes later.
42.25N 88.60W 06/25/2006 E0.88 INCH MCHENRY IL TRAINED SPOTTER
NICKLE HAIL AND STREET FLOODING ALONG HWY 20 IN EASTERN
MARENGO.
MESOSCALE DISCUSSION 1352 NWS STORM PREDICTION CENTER NORMAN OK 0200 PM CDT SUN JUN 25 2006
AREAS AFFECTED...SOUTHERN WI/FAR NORTHERN IL
CONCERNING...SEVERE THUNDERSTORM POTENTIAL
VALID 251900Z - 252030Z
AT LEAST AN ISOLATED SEVERE THREAT WILL EXIST ACROSS SOUTHERN WI INTO FAR NORTHERN IL THIS AFTERNOON. PRIMARY POTENTIAL WILL BE FOR LARGE HAIL...WITH STRONG WIND GUSTS/A TORNADO OR TWO/LOCALLY HEAVY RAINFALL POSSIBLE AS WELL. MONITORING FOR A POSSIBLE WATCH.
BENEATH COLD CORE /-15C AT 500 MB/...MODEST SURFACE HEATING IS CONTRIBUTING TO A RELATIVELY UNSTABLE/UNCAPPED AIRMASS ACROSS SOUTHERN WI...WITH MLCAPES TO 1000 J/KG. ALTHOUGH VERTICAL SHEAR IS WEAK...SUFFICIENT INSTABILITY/STEEP LAPSE RATE ENVIRONMENT WILL PROMOTE POTENTIAL FOR LARGE HAIL...AND POSSIBILITY FOR STRONG WIND GUSTS. THE POTENTIAL WILL ALSO EXIST FOR BRIEF/WEAK TORNADOES GIVEN AMBIENT VORTICITY/LARGE LOW LEVEL CAPE ENVIRONMENT...WITH 0-3 KM CAPES OF 100-150 J/KG ACROSS MUCH OF SOUTHERN WI. THIS WOULD PROBABLY BE MOST LIKELY WITH STORMS ON/INTERACTING WITH THE ARCING BOUNDARY/WIND SHIFT ACROSS SOUTHWEST/SOUTH CENTRAL WI INTO NORTHERN IL. IN FACT...THE STORM NEAR WISCONSIN DELLS APPEARS TO HAVE EXHIBITED SOME LOW LEVEL ROTATION OVER THE PAST HALF HOUR.
