Minnesota's Grass/Forest Fire Potential

The State Climatology Office has received several inquiries related to this season's grass and forest fire potential. Here are some of the important climatological issues to consider:

• the Spring of 1998 is off to a dry start in some areas. The latest precipitation maps show that portions of northern Minnesota have received less than 40 percent of normal rainfall.
• some areas of northeastern Minnesota experienced a dry 1997 growing season, creating an antecedent condition that enhances heavy-fuel fire potential. Of particular interest, the April through September precipitation departure map shows that areas of St. Louis, Lake, Cook, and Koochiching counties reported four to six inches less precipitation than their normal April - September totals of 20 to 22 inches.
• the anomalously warm and snow-free winter is led to an unusually early snow-free landscape. Snow depths throughout Minnesota were less than the 10th percentile for much of the season.
• the National Weather Service long-term outlook for May projects near normal temperatures and precipitation. The May through July outlook also offers no significant tilt away from the normals.

A number of people are attempting to connect this past Winter's anomaly with the active fire season of 1976. We do not see a good analogy between the winter of 1975-1976 and this winter (1997-98). February of the 75-76 season was pretty warm but Dec, Jan, and Mar were either normal or slightly cool. This year, Dec-Feb have seen all but a very few days above normal in temperature. Further, the winter of 1975-1976 received more than adequate snowfall, in fact snow depths were still greater than 2 feet across most of northern Minnesota well into March. However, April and May of 1976 were particularly dry followed by a brief reprieve in June, and then a resumption of very dry conditions for the remainder of 1976. This winter looks more like the winter of 1986-87.

We are examining what follows 'hot El Niño winters' in Minnesota. We have seen that the occurrence of El Niño conditions alone does NOT seem to be a very good indicator of what will happen in the following spring and summer. However, as we focus on the 6 hottest winters in Minnesota history, 5 of which were El Niño seasons, we see that the mid-summer period was either hot (1878, 1931, 1987, 1983) OR cold (1882, 1992) but not normal. Growing season precipitation totals following these warm winters were clustered in the middle of the long-term distribution.

Fire Weather Links

The Duluth office of the National Weather Service works closely with various land management agencies to provide specific weather forecasts for fire management across northeastern Minnesota and northwestern Wisconsin. Monitor their Northland Fire Weather page for very useful operational information.

National Weather Service forecast offices in the Twin Cities and Grand Forks issue fire weather forecast narratives daily.

The Minnesota Forest Fire Information Center page offered by the Minnesota Department of Natural Resources delivers timely information regarding various factors that influence wildfire behavior in Minnesota.

Return to the Climate Journal

mcwg@soils.umn.edu
URL:http://climate.umn.edu/doc/journal/fire_potential.html
Last modified: April 28, 1998