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!   

Convective outlook issued at 3:06 a.m. EDT. Yellow area: slight risk of severe thunderstorms between 8 a.m. EDT Wednesday and 8 a.m. EDT Thursday. Green area: non-severe thunderstorms.

All but extreme northern Indiana has a slight risk of severe thunderstorms Wednesday, according to the “Day 3 Convective Outlook” that the National Weather Service Storm Prediction Center (SPC) issued at 3:06 a.m. EDT. As you can see on the map at right, the slight risk area also includes all put a tiny part of northwestern Ohio and large parts of West Virginia, Kentucky and Illinois. The slight risk area includes all counties in IMO SKYWARN quadrant two, although northern Whitley County is not in the slight risk area.

If severe thunderstorms develop in the slight risk area, meteorologists expect it to happen Wednesday afternoon and/or evening, after daytime heating destabilizes the atmosphere. They indicate that damaging straight-line winds and large hail will be the greatest risks Wednesday.

We’ll know more about Wednesday’s severe weather risk when the SPC issues its first “Day 2 Convective Outlook” for the period, early tomorrow morning (the link above won’t work until after the SPC issues the outlook at about 2 a.m.).

BULLETIN - IMMEDIATE BROADCAST REQUESTED
FLOOD WARNING 
NATIONAL WEATHER SERVICE NORTHERN INDIANA 
1119 AM EDT THU MAY 15 2014

...THE NATIONAL WEATHER SERVICE IN NORTHERN INDIANA HAS ISSUED A 
FLOOD WARNING FOR THE FOLLOWING RIVERS...

  SAINT JOSEPH RIVER OHIO ABOVE NEWVILLE AFFECTING ALLEN...DE KALB AND
  DEFIANCE COUNTIES


.HEAVY RAINS THIS PAST WEEK HAVE CAUSED THE SAINT JOSEPH RIVER OHIO
ABOVE NEWVILLE TO RISE. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

SAFETY MESSAGE...NEVER DRIVE VEHICLES THROUGH FLOODED AREAS.  THE 
WATER MAY BE TOO DEEP TO ALLOW SAFE PASSAGE. NEVER ALLOW CHILDREN TO 
PLAY IN OR NEAR FLOOD WATERS. STAY TUNED TO NOAA WEATHER RADIO OR 
LOCAL MEDIA FOR FURTHER STATEMENTS AND UPDATED FORECASTS.

DETAILED RIVER FORECASTS AND MORE INFORMATION CAN BE FOUND ON THE 
INTERNET AT WWW.WEATHER.GOV/IWX. RIVER INFORMATION CAN BE FOUND UNDER
THE LEFT MENU BAR UNDER CURRENT CONDITIONS RIVERS AND LAKES AHPS.

ALL TIMES ARE IN EASTERN TIME. THIS STATEMENT WILL BE UPDATED IN 
ABOUT 24 HOURS OR SOONER IF NECESSARY.

&&

INC003-033-OHC039-161519-
/O.NEW.KIWX.FL.W.0069.140516T1200Z-140519T0600Z/
/NVLI3.1.ER.140516T1200Z.140517T0600Z.140518T0600Z.NO/
1119 AM EDT THU MAY 15 2014

THE NATIONAL WEATHER SERVICE IN NORTHERN INDIANA HAS ISSUED A 

* FLOOD WARNING FOR 
  THE SAINT JOSEPH RIVER OHIO ABOVE NEWVILLE
* FROM FRIDAY MORNING TO LATE SUNDAY NIGHT.
* AT 10 AM THURSDAY THE STAGE WAS 9.0 FEET AND RISING.
* MINOR FLOODING IS FORECAST.
* FLOOD STAGE IS 12.0 FEET.
* FORECAST...THE RIVER WILL RISE ABOVE FLOOD STAGE FRIDAY MORNING  
  AND CREST NEAR 12.3 FEET AROUND 2 PM SATURDAY MAY 17 AND FALL 
  BELOW FLOOD STAGE AROUND 2 AM SUNDAY MAY 18.
* AT 12.0 FEET...DEKALB COUNTY ROAD 42 ABOUT 3 MILES NORTHEAST OF 
  NEWVILLE FLOODS. AGRICULTURAL AND LOW LANDS FLOOD ALONG THE ST. 
  JOSEPH RIVER TO THE CEDARVILLE RESERVOIR.
* THIS CREST COMPARES TO A PREVIOUS CREST OF 12.1 FEET WHICH OCCURRED 
  ON DEC 14 2007.

Thunderstorms are expected to increase in coverage through the afternoon as a pre-frontal air mass gradually destabilizes. Though a few marginally severe hail or wind events will be possible with stronger cells, a watch is not anticipated, according to a mesoscale discussion the National Weather Service Storm Prediction Center issued at 12:37 a.m. EDT.

Radar showed thunderstorms gradually increasing in a band from southern lower Michigan south-southwestward into southwestern Indiana, along a slowly advancing surface cold front. Ahead of the front and storms, the atmosphere is becoming moderately unstable and sunshine is heating moist air, with dew points are in the upper 60s.

Although the thermodynamic environment will support additional increases in storm coverage and/or intensity, the high-altitude winds will limit widespread severe potential. As such, somewhat weakly organized storms are expected. Thus, with only an isolated severe risk expected, a watch will likely remain unnecessary across the region.