A now stationary front hanging along the Indiana-Michigan line is forecast to slowly move south today. As daytime heating occurs, thunderstorms should form and mature along and south of the front, according to the “Day 1 Convective Outlook” that the National Weather Service (NWS) Storm Prediction Center issued at 1:59 a.m. EDT.

Available moisture (dew points in the 60s) and atmospheric instability (forecast to be above 1,000 j/kg by 1 p.m. EDT) might allow for pulse-type storms and perhaps some multicell storms capable of locally damaging winds and perhaps marginal hail. Wind shear today, however, is insufficient to support even a slight risk of severe thunderstorms in the convective outlook.

The northern Indiana NWS office agrees that an isolated strong to severe storm and heavy rainfall are possible this afternoon and evening anywhere in its 37-county warning area, according to the “Hazardous Weather Outlook” the office issued at 5:40 a.m. EDT. The outlook indicates, however, that spotter activation is not anticipated.

Much of Indiana and Ohio, as well as parts of other nearby states, have a slight risk of severe weather between 9 a.m. EDT today and 8 a.m. EDT tomorrow, according to the “Day 1 Convective Outlook” that the National Weather Service (NWS) Storm Prediction Center (SPC) issued at 8:40 a.m. today.

The main threats are isolated damaging strait-line wind gusts and hail. In south central Indiana, hail stones could be larger than two inches in diameter.

The slight risk area includes includes parts or all of the following counties in IMO SKYWARN quadrant two:

• Huntington
• Wells
• Adams
• Van Wert
• Allen (Ohio)
• Blackford
• Jay

The slight risk area does not currently include any part of Allen County, Indiana or any Indiana counties to the north or west of Allen County.
 
Scattered thunderstorms should begin developing by late afternoon and storms might continue into the evening. SKYWARN spotter activation might be needed this afternoon, according to the “Hazardous Weather Outlook” that the northern Indiana NWS office issued at 4:47 a.m. EDT.

We’ll get our next look at the severe weather risks for today when the SPC issues an updated convective outlook by 12:30 p.m. EDT.

The northern half of Indiana and adjacent parts of Illinois, Michigan and Ohio have a slight risk of severe thunderstorms between 9 a.m. EDT today and 8 a.m. EDT tomorrow, according to the “Day 1 Convective Outlook” that the National Weather Service (NWS) Storm Prediction Center (SPC) issued at 8:44 a.m. EDT. In addition, almost all of Indiana and all of Ohio have a slight risk between 8 a.m. EDT Wednesday and 8 a.m. EDT Thursday, according to the “Day 2 Convective Outlook” that the SPC issued at 1:27 a.m. EDT.

Today (Day 1)

The greatest risks today in northeastern Indiana and surrounding areas are damaging straight-line winds and large hail. These could occur late this evening and overnight as storms that form in Illinois this afternoon form a squall line complex and move across Indiana, southern Lower Michigan and northwestern Ohio. That line “could produce numerous damaging wind events,” according to the convective outlook. Brief, small tornadoes sometimes form at the leading edges of such lines of storms.

As you can see on the maps at right, here are the probabilities of various hazards occurring within 25 miles of a point:

• 30 percent probability of damaging thunderstorm winds or wind gusts of 50 knots (58 mph) or higher.
• 15 percent to 30 percent probability of one inch diameter hail or larger.
• 2 percent to 5 percent probability of a tornado.

Also, parts of north central and northwestern Indiana and southern Lower Michigan have a 10 percent or greater probability of two inch diameter hail or larger.

In case you haven’t previously seen an explanation of the relevance of these seemingly low numbers, read this explanation on the SPC website.

SKYWARN storm spotter activation might be needed this evening and overnight, according to the “Hazardous Weather Outlook” that the northern Indiana NWS office issued at 5:40 a.m. EDT. Today’s slight risk area includes the entire 37-county warning area of the northern Indiana office.

The SPC will issue an updated day 1 outlook by 2:30 p.m.

Tomorrow (Day 2)

The SPC forecasts a second round of storms to form at around 2 p.m. EDT tomorrow (Wednesday). The storms might ultimately evolve into line segments as they spread southeastward. If an organized squall line matures enough, a “widespread wind event could unfold across the region,” according to the “Day 2 Convective Outlook.”

As you can see on the map at right, the probably of some form of severe weather across the area, including all of IMO SKYWARN quadrant two, is 15 percent. Day two outlooks do not break down the probability by hazard type.

The SPC will issue an updated day 2 outlook by 1:30 p.m. today.

Actions to take

Because today’s severe weather might not arrive until after bedtime, it is important that all residents of the risk area have some way to be awakened should the NWS issue any severe weather warnings. If you have a NOAA Weather Radio, make sure it’s working (see if you can hear the NWS transmissions) and make sure its batteries are good (in case of a storm-related power outage). If you don’t have a weather radio, they’re still on sale at area Walgreens and Kroger stores, among other retailers. Also, some smartphone apps emit loud enough alerts to wake some people.

This evening, overnight tonight and tomorrow afternoon, any time you’ll be away from a weather radio, keep a television or broadcast radio tuned to a local station, so you’ll know about any watches and warnings.

If you’re a SKYWARN storm spotter, fuel up your vehicle and check all of your equipment so you’ll be ready for action!