URGENT - IMMEDIATE BROADCAST REQUESTED
   SEVERE THUNDERSTORM WATCH NUMBER 375
   NWS STORM PREDICTION CENTER NORMAN OK
   335 PM CDT MON JUN 30 2014

   THE NWS STORM PREDICTION CENTER HAS ISSUED A

   * SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 
     NORTHERN AND EASTERN ILLINOIS
     NORTHWEST AND NORTH CENTRAL INDIANA
     SOUTHWEST LOWER MICHIGAN
     EASTERN WISCONSIN
     LAKE MICHIGAN

   * EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 335 PM UNTIL
     900 PM CDT.

   ...THIS IS A PARTICULARLY DANGEROUS SITUATION...

   * PRIMARY THREATS INCLUDE...
     WIDESPREAD DAMAGING WINDS AND SCATTERED SIGNIFICANT GUSTS TO 80
       MPH LIKELY
     ISOLATED LARGE HAIL EVENTS TO 1.5 INCHES IN DIAMETER POSSIBLE
     A TORNADO OR TWO POSSIBLE

   THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70
   STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES NORTHEAST OF
   MILWAUKEE WISCONSIN TO 65 MILES SOUTH SOUTHWEST OF VALPARAISO
   INDIANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
   ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
   FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
   AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
   THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
   AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
   DO PRODUCE TORNADOES.

   &&

   OTHER WATCH INFORMATION...CONTINUE...WW 373...WW 374...

   DISCUSSION...FAR ERN IA DERECHO-PRODUCING MCS EXPECTED TO MOVE
   MAINLY E THROUGH EARLY TNGT. THE CONVECTIVE SYSTEM WILL ENCOUNTER
   SLIGHTLY LESS UNSTABLE LOW-LVL ENVIRONMENT OVER NE IL/SE WI RELATIVE
   TO THAT OVER ERN IA/WRN IL. BUT GIVEN EXISTING STRENGTH OF
   CONVECTIVE SYSTEM...AND LIKELIHOOD FOR SOME INCREASE IN THE MEAN
   FLOW OVER NRN IL AS NW MO UPR IMPULSE APPROACHES...EXPECTED AN
   ORGANIZED BAND OF SVR STORMS TO CONTINUE E AT LEAST AS FAR AS LK MI.
   BACKING OF DEEP FLOW AHEAD OF MO IMPULSE...AND CONTINUED NWD SPREAD
   OF LOW-LVL MOISTURE...FURTHER SUGGEST THAT THE SQLN COULD BUILD A
   BIT FARTHER N INTO WI WITH TIME.

   AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
   TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70
   KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM
   MOTION VECTOR 27045.

Probabilities of damaging straight-line thunderstorm winds of 58 mph or greater within 25 miles of a point. Brown area: five percent. Yellow: 15 percent. Red: 30 percent. Purple: 45 percent (moderate risk) plus a 10 percent chance of “significant” gusts to 75 mph or greater. Highlighted counties: county warning area of the northern Indiana NWS office. Source: SPC “Day 1 Convective Outlook,” 12:33 p.m. EDT.

A larger portion of northwestern Indiana has a moderate risk of severe weather this afternoon and tonight, according to the updated “Day 1 Convective Outlook” that the National Weather Service (NWS) Storm Prediction Center (SPC) issued at 12:33 p.m. EDT. Meanwhile, the risk for IMO SKYWARN quadrant two did not change from the previous outlook.

The primary threat remains damaging straight-line thunderstorm winds or gusts of 58 mph or stronger but there’s also a risk of one-inch or larger hail and an occasional tornado.

In quadrant two counties covered by the slight risk area, the probabilities of severe weather within 25 miles of a point remain at 15 percent for winds of 58 mph or higher and one-inch or larger hail and two percent for a tornado.

The northwestern counties that are in the a moderate risk area have a 45 percent probability of 58 mph thunderstorm winds and a 10 percent probability of gusts to 75 mph or higher.

The next update to the convective outlook for today is due by 4 p.m. EDT.

Probabilities of damaging thunderstorm winds or wind gusts of 50 knots (58 mph) or higher within 25 miles of a point. Purple area: 45 percent. Red area: 30 percent. Yellow area: 15 percent. Brown area: five percent. Grey area outlined in black: 10 percent or greater probability of “significant” wind gusts of 75 mph or greater within 25 miles of a point. Highlighted counties: County warning area of the northern Indiana NWS office.

See an update to this post.

There is a slight risk of severe thunderstorms in northeastern, northwestern and north central Indiana 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 8:52 a.m. EDT.

The greatest threats are damaging straight-line thunderstorm winds of 58 mph or greater and hail of one inch or greater diamter. A small part of northwestern Indiana has an enhanced risk of “significant” damaging thunderstorms winds (gusts of 75 mph or greater).

The slight risk area includes the following counties in IMO SKYWARN quadrant two: Allen (Ind.), Whitley, Huntington, Wells, Adams, Blackford and parts of Jay and Paulding.

The counties (or parts of counties) listed above have the following probabilities of the following types of severe weather within 25 miles of a point:

Some thunderstorms might occur this afternoon but the chance is greatest tonight, according to the “Hazardous Weather Outlook” that the NWS northern Indiana office issued at 4:28 a.m. EDT. That outlook indicates that SKYWARN storm spotter activation will likely be needed tonight.

As always when this amount of risk is present, people planning outdoor activities this afternoon and tonight should assure that they have a way of learning of any watches or warnings that the NWS might issue and a way to quickly take shelter. SKYWARN storm spotters should fuel up their vehicles, make sure their communications equipment is ready and review reporting criteria and procedures.

The SPC will next update its convective outlook for today by 12:30 p.m. EDT.

Probability of damaging thunderstorm winds or wind gusts of 50 knots (58 mph) or higher within 25 miles of a point. Learn why 15 percent is meaningful.

After issuing “Day 1 Convective Outlooks” at 2 a.m. and 9 a.m. EDT that indicated no risk of severe weather today in Indiana, the National Weather Service (NWS) Storm Prediction Center (SPC) issued a revised outlook at 12:30 p.m. that indicated a slight risk of severe weather in most of the northern half of Indiana. That risk continues in the updated outlook that the SPC issued at 3:45 p.m. EDT.

The primary threat is damaging straight-line thunderstorm winds of 58 mph or stronger. The outlook indicates a 15 percent probability of such winds within 25 miles of a point. The probably of of a tornado in the area is less than two percent and the probability of large hail is less than five percent.

The slight risk area includes all of the 37-county warning area of the northern Indiana NWS office, except for a bit of the northwest corner. The slight risk area includes all county in IMO SKYWARN quadrant two.

The latest “Hazardous Weather Outlook” from the northern Indiana NWS office, issued at 12:36 p.m. EDT, indicated that SKYWARN spotter activation was not anticipated at that time.

There is a chance for thunderstorms today and tonight in northeastern Indiana, southern Lower Michigan and northwestern Ohio, but forecasters do not expect the storms to be severe, according to the “Hazardous Weather Outlook” that the northern Indiana National Weather Service (NWS) office issued at 5:25 a.m.

Wind gusts to 45 mph are possible, however, with the strongest storms, so it would be a good idea to put away any lightweight lawn furniture or anything else that could blow away. Some storms could also bring locally heavy rainfall.

There is a chance for more storms tomorrow (Tuesday, June 25), a few of which could produce isolated wind gusts approaching severe limits (58 mph). If that happens, it will most likely be east of Interstate 69.

NWS meteorologists did not anticipate any activation of SKYWARN storm spotters at the time they wrote the outlook.

Heavy rainfall from thunderstorms could cause localized flooding in northeastern Indiana, southern Lower Michigan and northwestern Ohio today, according to the “Hazardous Weather Outlook” that the northern Indiana office of the National Weather Service (NWS) issued at 5:43 a.m. Some strong storms this afternoon and early evening could produce wind gusts to 45 mph. While some storms might be strong, forecasters do not expect any of them to reach severe thunderstorm criteria (winds of at least 58 mph and/or hail of at least one inch in diameter).