The 2009 severe weather season around the region was unusually quiet, with the total number of severe weather reports well below normal. The total number of severe weather reports for the Grand Forks NWS county warning area (CWA), including hail ¾ of an inch or larger (note that the new severe hail criteria was raised to 1 inch in 2009), high winds of 58 mph or greater, and tornado reports totaled 145. The average number of severe weather reports since 1996 is 397 reports, or about 250 severe weather reports below normal.
This year will go down as the quietest severe weather season since the Grand Forks National Weather Service office has been in Grand Forks. The main reason for this was a persistent flow of colder air from Canada that resulted in temperatures much below normal through the summer months. This colder air inhibited thunderstorm formation, especially severe thunderstorms that require heat, moisture and instability to cause large thunderstorms to grow and produce severe weather.
Below is a graph depicting the severe weather reports from 1996 through this year. The most active severe weather season over the past 13 years was 2001, when a whopping 705 severe weather reports occurred. The average number of severe weather reports from 1996 through this year is indicated with a blue line.
Severe weather reports from 1996-2009 in the Grand Forks CWA.