All of Indiana, plus parts of Michigan and Ohio, including all 37 counties served by the northern Indiana National Weather Service (NWS) office, are at high risk of severe weather between 9 a.m. EST today and 8 a.m. EST tomorrow, according to the Day 1 Convective Outlook that the NWS Storm Prediction Center (SPC) issued at 7:59 a.m. today.

High risk areas in a convective outlook are not unusual in Oklahoma but it’s very unusual for the SPC to indicate a high risk in Indiana.

The outlook gives the following probabilities for the high-risk area:

• Probability of a tornado within 25 miles of a point: 30%.
• Probability of EF2 – EF5 tornadoes within 25 miles of a point: 10% or greater.
• Probability of damaging thunderstorm winds or wind gusts of 50 knots (58 mph) or higher within 25 miles of a point: 45%
• Probability of wind gusts 65 knots (74.8 mph) or greater within 25 miles of a point: 10% or greater.
• Probability of hail 1″ or larger within 25 miles of a point: 15%

What do these percentages really mean? Read this excellent explanation on the SPC website.

A Public Severe Weather Outlook that the SPC issued at 3:49 a.m. EST captures the situation well in layman’s terms. You can read it below. I’m off to worship after I write this post but I’ll try to add additional information to this blog as time permits. Meanwhile, stay tuned to NOAA Weather Radio, and/or your favorite local broadcast station for any watches or warning. Also, the northern Indiana NWS office is putting out a constant stream of information on its Facebook page and Twitter feed.

PUBLIC SEVERE WEATHER OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0249 AM CST SUN NOV 17 2013

   ...SEVERE THUNDERSTORMS EXPECTED OVER PARTS OF THE MID-MISSISSIPPI
   AND OHIO VALLEYS INTO MICHIGAN TODAY THROUGH EARLY TONIGHT...

   The NWS Storm Prediction Center in Norman, Oklahoma is forecasting
   the development of a few strong, long-track tornadoes over parts of
   the Mid-Mississippi and Ohio Valleys into Michigan today through
   early tonight.

   The areas most likely to experience this activity include:

          Illinois
          Indiana
          Northern and Western Kentucky
          Lower Michigan
          Ohio
          Southeast Wisconsin

   Surrounding this greatest risk region, severe thunderstorms will
   also be possible from parts of Wisconsin, Iowa, Missouri, Arkansas,
   Mississippi, Alabama, and Tennessee northeastward across much of the
   Appalachians to the lower Great Lakes.

   A potent jet stream disturbance with wind speeds in excess of 120
   knots will sweep east across the central Plains today and across the
   Ohio Valley and northern half of the Appalachians tonight. As this
   occurs, a surface low now over the mid-Mississippi Valley will
   rapidly intensify and accelerate northeastward, reaching northern
   Michigan early tonight and western Quebec Monday morning.

   East of the low, increasingly warm and humid air at the surface will
   spread north across the Tennessee and Ohio Valleys, contributing to
   very unstable conditions over a large part of the east central
   United States. Coupled with daytime heating and ascent provided the
   jet stream impulse, the environment will become very favorable for
   severe thunderstorms --- especially along and ahead of fast-moving
   cold front trailing southward from the low into the mid-Mississippi
   and Ohio Valleys.

   Given the degree of thermodynamic instability, and the strength and
   character of the winds through the depth of the atmosphere, many of
   the storms will become supercells. Some of these will be capable of
   producing strong tornadoes --- in addition to large hail and swaths
   of damaging surface winds.  

   The storms are expected to consolidate into one or two extensive
   lines later today into tonight --- extending the threat for damaging
   winds and isolated tornadoes eastward into the Appalachians by early
   Monday.

   State and local emergency managers are monitoring this potentially
   very dangerous situation. Those in the threatened area are urged to
   review severe weather safety rules and to listen to radio,
   television, and NOAA Weather Radio for possible watches, warnings,
   and statements later today.