Yellow area: Slight risk of severe thunderstorms today and tonight. Green area: Non-severe thunderstorms.

Portions of northern Indiana, southern Lower Michigan and northwestern Ohio have a slight risk of severe thunderstorms this afternoon and evening, according to the “Day 1 Convective Outlook” that the National Weather Service (NWS) Storm Prediction Center issued at 8:39 a.m. EDT. The main threats from these storms will be damaging straight-line winds and hail. In addition to these, torrential rain is possible, according to the “Hazardous Weather Outlook” that the northern Indiana NWS office issued at 8:58 a.m. EDT.

That outlook also indicates that SKYWARN spotter activation might be needed later this afternoon and this evening.

The slight risk area includes Allen and Whitley Counties of Indiana and counties to the west and north of them. It also includes Paulding and Putnam Counties of Ohio and counties to the north.

FLOOD ADVISORY
NATIONAL WEATHER SERVICE NORTHERN INDIANA
1045 PM EDT SUN MAY 11 2014

ALLEN IN-WHITLEY IN-HUNTINGTON IN-
1045 PM EDT SUN MAY 11 2014

THE NATIONAL WEATHER SERVICE IN NORTHERN INDIANA HAS ISSUED AN

* URBAN AND SMALL STREAM FLOOD ADVISORY FOR...
  SOUTHWESTERN ALLEN COUNTY IN NORTHEAST INDIANA
  NORTHERN HUNTINGTON COUNTY IN NORTHEAST INDIANA
  WHITLEY COUNTY IN NORTHEAST INDIANA

* UNTIL 145 AM EDT

* AT 1041 PM EDT NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED    
  SLOW MOVING THUNDERSTORMS WITH VERY HEAVY RAIN OVER THE WARNED     
  AREA. RAINFALL RATES OF 1 TO 2 INCHES PER HOUR WILL BE POSSIBLE    
  THROUGH THE EARLY OVERNIGHT WHICH MAY CREATE LOCALIZED FLOODING. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

EXCESSIVE RUNOFF FROM THESE STORMS WILL CAUSE FLOODING OF SMALL
CREEKS AND STREAMS...HIGHWAYS AND UNDERPASSES. ADDITIONALLY...
COUNTRY ROADS AND FARMLANDS ALONG THE BANKS OF CREEKS AND STREAMS AND
OTHER LOW LYING AREAS ARE SUBJECT TO FLOODING.

Almost all of Indiana has a slight risk of severe thunderstorms late this afternoon and this evening, according to the Day 1 Convective Outlook the National Weather Service Storm Prediction Center issued at 12:22 p.m. EDT. 

Northern Indiana is no longer at risk of severe weather today, according to an updated “Day 1 Convective Outlook” the National Weather Service Storm Prediction Center issued at 12:20 p.m. EDT. As you can see on the map at right, the newly-draw slight risk area includes most of the southern half of Indiana but no longer includes northern Indiana.

Atmospheric instability appears to be insufficient for severe thunderstorms to develop in northern Indiana this afternoon, in part because of insufficient sunshine to create surface heating.

Non-severe thunderstorms remain forecast, however. Some of these could contain winds to 40 mph and small hail.

See an update to this post.

Almost the entire state of Indiana, including most northeastern counties, has a slight risk of severe thunderstorms between 8 a.m. EDT this morning and 8 a.m. EDT tomorrow morning, according to the “Day 1 Convective Outlook” that the National Weather Service (NWS) Storm Prediction Center issued at 7:50 a.m. today. The storms are mostly likely this afternoon and through this evening.

The main threat is damaging straight-line winds and large hail. The Indiana portion of the slight risk area has only a two percent probability of a tornado within 25 miles of a point (less than a “slight” risk) and a 15 percent probability of either of the following within 25 miles of a point: damaging thunderstorm winds or wind gusts of 50 knots (58 mph) or greater or one inch diameter or larger hail. Remember that compared the precipitation probabilities we see all the time, 15 percent might not seem impressive, but it’s probably at least 10 times greater than our normal probability for this date. Read more about severe weather probabilities

As I write this, the sky is overcast, which limits the potential for severe storms later today. But if the clouds break up later, the risk of severe weather will rise as the amount of sunshine increases.

As you can see on the map above right, the slight risk area covers almost all of Indiana, with the few exceptions including the northernmost tier of counties (Steuben west to Lake), and a few counties in extreme southeastern Indiana (near Cincinnati). In IMO SKYWARN quadrant two, the slight risk area includes all Indiana counties and Paulding and Van Wert Counties of Ohio.

SKYWARN storm spotter activation might be needed by this afternoon and evening, according to the “Hazardous Weather Outlook” that the northern Indiana NWS office issued at 4:27 a.m. EDT.

What to do with this information
Make sure that if the NWS issues any watches or warnings today, you’ll know about it. If you won’t be near your weather alert radio for any part of the day or evening, keep a television or broadcast radio tuned to a local station. You can also receive watches and warnings numerous other ways (see my earlier blog, “Better alternatives to tornado sirens“).

If you’re a trained NWS storm spotter, check your gear and fuel up your vehicle this morning, so you’ll be ready to go, should spotter activation occur this afternoon or evening.