National Weather Service Weather Forecast Office

TORNADO - A violently rotating column of air, usually forming a pendant from a cumulonimbus cloud, whose circulation reaches the ground. It nearly always starts as a funnel cloud and may be accompanied by a loud roaring noise. On a local scale, it is the most destructive of all atmospheric phenomena.

FUNNEL CLOUD - A rotating column of air, forming a pendant from a cumulus or cumulonimbus cloud, whose circulation does not reach the ground.

TORNADO WATCH - Conditions are favorable for tornado development. Remain alert for approaching storms.

TORNADO WARNING - Radar has indicated a tornado or a tornado has been spotted. Take cover now.

 SEVERE THUNDERSTORM - A thunderstorm accompanied by winds (sustained or gusts) of 58 mph (50 knots) or more and hail 1 inch in diameter or larger. Structural wind damage may be used to infer the occurrence of a severe thunderstorm.

SQUALL LINE - A line of thunderstorms or squalls which may extend over several hundred miles.

SEVERE THUNDERSTORM WATCH- Conditions are favorable for tornado development. Remain alert for approaching storms.

SEVERE THUNDERSTORM WARNING - Radar has indicated a severe thunderstorm or severe weather has been reported. Take cover now.

WATERSPOUT - A rotating column of air, usually forming a pendant from a cumulus or cumulonimbus cloud, which forms over a body of water, and whose circulation reaches the water.

DOWNBURST - A strong downdraft from a cumulonimbus cloud which induces damaging winds on or near the ground.

MACROBURST - A large downburst with the diameter of outflow 2 1/2 miles or larger and damaging winds lasting 5 to 20 minutes. Intense macrobursts can cause tornado-force damage.

MICROBURST - A small downburst with the diameter of outflow less than 2 1/2 miles and peak winds lasting only 2 to 5 minutes. They may induce dangerous wind and downflow wind shears which can affect aircraft performance.

FLASH FLOOD - A flood which follows a heavy or excessive rainfall, a dam or levee failure, or sudden release of water impounded by an ice jam, within a few hours. There is nothing in the National Weather Service definition that says a flash flood must be a "wall of water."

WINTER STORM WARNING FOR HEAVY SNOW -
Northern and Central Indiana:
6 inches or more in 12 hours or less
8 inches or more in 24 hours or less

Southern Indiana: 4 inches or more in 12 hours or less
6 inches or more in 24 hours or less

WINTER WEATHER ADVISORY FOR  SNOW  -
Northern and Central Indiana: 3 to 5 inches in 12 hours
Southern Indiana: Less than 4 inches in 12 hours

BLIZZARD WARNING - Sustained winds or frequent gusts to 35 mph or more for at least 3 hours and considerable falling and/or blowing snow reducing visibility frequently to less than 1/4 mile.

ICE STORM WARNING - Ice accumulation of 1/4 inch or more on all surfaces. Brings down wires.

HIGH WINDS - Sustained winds of 40 mph or greater or winds gusting to 58 mph or greater.

WINTER WEATHER ADVISORY FOR BLOWING SNOW - Visibilities intermittently at or below 1/4 mile due to blowing snow with winds less than 35 mph.

WIND CHILL ADVISORY - Values -15 to -24 with minimum wind speeds of 10 mph

WIND CHILL WARNING - Values -25 or below with minimum wind speeds of 10 mph

DEGREE DAYS -The amount of deviation in the average daily temperature from 65 degrees. Average temperatures greater than 65 degrees yield cooling degree days where average daily temperatures less than 65 degrees yield heating degree days. An example: The high temperature for a day is 75 degrees and the low temperature for the day is 65. That gives an average temperature for the day of 70 degrees and results in 5 cooling degree days. In contrast, an average daily temperature of 60 degrees would result in 5 heating degree days. Degree day totals are typically tabulated on a daily, monthly, seasonal and yearly basis. Departures from normal for those time periods are also typically tabulated. Check out our Climate page to get degree day totals for the past 12 months.