SPS Issued for Far NE Illinois

Initial storm warned for after ProbSvr topped out at 82 percent only generated pea sized hail before weakening again. The second storm of interest topped out at 61 percent on ProbSvr. Like the first cell, this storm initially peaked and slowly weakend in a multi-storm cluster environment. Due to the close proximity of nearby cells, the Lightning Jump parameters were not as useful.

Update: A delayed report of quarter sized hail arrived for this storm plus another that verfied the first warning.  This increased confidence in the use of ProbSVR for values that was 70 percent or greater.  This storm moved offshore with values that dipped slightly after producing the quarter sized hail report, but then picked up again with values consistently exceeding 70 percent.  The delay of reports received contaminated our decision making and reduced lead times on storms up this point.

Forecaster: Manbearpig