(12:20 a.m.) — Logan County’s Severe Thunderstorm Warning has been extended to 12:45 a.m. Champaign is under is also under a warning until 12:45 a.m.

(11:30 p.m.) — Shelby and Logan counties are under a Severe Thunderstorm Warning until 12:15 a.m.

(11:00 p.m.) — Mercer County is under a Severe Thunderstorm Warning until 11:45 p.m.

(10:10 p.m.) — A Severe Thunderstorm Watch has been issued for Champaign, Logan, Mercer and Shelby counties until 3 a.m. The National Weather Service said a second round of storms is expected to impact the area between 11 p.m. and midnight.

(9:05 p.m.) – A Flood Warning for Butler County has been issued until 5 a.m. Tuesday. A Flood Advisory has been issued for Butler, Greene, and Montgomery counties until 9:30 p.m. Monday night.

(9:04 p.m.) — The National Weather Service have cleared the Severe Thunderstorm Watch Monday evening.

(7:07 p.m.) — The National Weather Service have cleared the Severe Thunderstorm Warning Monday evening.

A Excessive Heat Warning is in effect for the following counties: Butler, Champaign, Clark, Clinton, Darke, Greene, Mercer, Miami, Montgomery, Preble, Shelby, Warren and Wayne until noon Tuesday, June 14

A Heat Advisory is in effect for Butler, Darke, Preble, and Wayne counties.

There are two big weather stories we are tracking this week: the potential for severe thunderstorms today, and the building heat and humidity.

First, the thunderstorm potential. These are not a given, but if they do get going, there is a decent chance they will become strong to severe. Most of the Miami Valley is in a Slight Risk, while the northern counties have been upgraded to an Enhanced Risk:

There is a ton of instability here during the afternoon hours:

This will help any storms reach severe limits, and produce winds in excess of 60 mph. While damaging wind is the main threat, there will also be the chance for hail and isolated tornadoes. Very heavy rain could lead to localized flooding.

There looks to be two possible rounds of storms. One would be in the late afternoon–generally between 4pm and 8pm:

Another round will be during the first part of the overnight, and will mostly likely be across the northern Miami Valley, as a complex of thunderstorms moves in from the northwest:

After that, the severe threat will diminish, and we expect dry weather and abundant sunshine on Tuesday. Temperatures will soar, well into the 90s. The heat index values will be between 105 and 110 degrees both Tuesday and Wednesday:

It will be our first official heat wave of the summer (three days at/above 90-degrees), and we have the potential to break record highs Tuesday (R 94°) and Wednesday (R 96°). This type of heat is dangerous, and it’s important to take frequent breaks if you have to work outside during this time. Try to find the shade or air conditioning if you can.  Drink plenty of water, and check on the elderly and keep an eye on kids and pets. 

Thunderstorms will be possible again on Thursday, and behind that system, temperatures will cool a bit for Friday and the weekend.