Warning issued for Kane County UPDATED

This storm had been holding steady with a reflectivity core of around 55 dBZ at -20C (according to NUCAPS profiles). There was also a faint TBSS for a few volume scans as well. ProbSevere was in the 50% neighborhood and there were a few lightning jumps around 1 or 2 sigma. We had been hesitant to issue warnings on this storm because previous storms that looked similar failed to produce severe weather.

At 2230z, ProbSevere spiked to 82%, there was a 3-sigma lightning jump, and the reflectivity core intensified. Those triggers were enough to prompt a Severe Thunderstorm Warning.

---UPDATE---

Shortly after the warning was issued, 1" hail was reported within the warning. As mentioned in a previous blog post, we had warned on a storm with similar characteristics as this one that did not verify, or so we thought. The first storm we warned on, which looked very similar to this storm, did actually verify, but we did not get the report until well beyond an hour after the first warning expired. Had we known that our first warning verified, we would have had a warning out for this storm earlier.

---UPDATE---

This storm continued into the Chicago metro with borderline severe characteristics. Shortly before the storm exited the original warning, ProbSevere spiked to 85% and there was a 4-sigma lightning jump. Despite a lack-luster reflectivity signature, the ProbSevere and lightning jump were enough to prompt a new warning for this storm.

-Toki Wartooth