19 APRIL 2011—Waterloo, Iowa Forecast

Today: Snow before 1pm, then rain and snow. Some thunder is also possible. High near 37. Windy, with a east northeast wind around 21 mph, with gusts as high as 29 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 1 to 3 inches possible.

—–IN IOWA, YOU CAN EXPERIENCE A 165 Degree, TEMPERATURE RANGE THROUGH-OUT THE YEAR

The record low temperature for the state is –47°F (–44°C), established at Washta on 12 January 1912 and recorded again on Elkader on 3 February 1996; the record high is 118°F (48°C), registered at Keokuk on 20 July 1934.

Thundersnow, also known as a winter thunderstorm or a thunder snowstorm, is a relatively rare kind of thunderstorm with snow falling as the primary precipitation instead of rain. It typically falls in regions of strong upward motion within the cold sector of an extratropical cyclone, where the precipitation consists of ice pellets rather than snow. Thermodynamically, it is not different from any other type of thunderstorms but the top of the cumulonimbus are usually quite low.

HOW THUNDERSNOW IS PRODUCED

One unique aspect of thundersnow is that the snowfall acts as an acoustic suppressor of the thunder. The thunder from a typical thunderstorm can be heard many miles away, while the thunder from thundersnow can usually only be heard within a two to three mile radius from the lightning. In the United States, March is their peak month of formation, and on average, only 6.3 events are reported per year.

—-For the United States, the extremes are 134 °F (56.7 °C) in Death Valley, California and −79.8 °F (−62.1 °C) recorded in Prospect Creek, Alaska.

—-The largest 2-minute temperature change of 49 °F (27.2 °C) occurred in Spearfish, South Dakota, a rise from -4 to 45 °F (-20 to 7.2 °C).

—-The largest recorded temperature change over a 24-hour period occurred on January 15, 1972 in Loma, Montana, when the temperature rose from -54 to 49 °F (-47.8 to 9.4 °C).

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