Near-critical fire weather and spring dip conditions contribute to spring wildfires

Wildfire conditions throughout northern Minnesota continue to linger as many areas remain below average in precipitation. While recent rainfall brought some relief to the drought-stricken northwest, rain was spotty for many areas. Tuesday’s near-critical fire conditions are a good reminder that many areas remain in high fire danger despite the appearance of green-up conditions.

“It’s not uncommon for wildfires to become more active in northern forested areas this time of year,” said Travis Verdegan, fire behavior specialist with the Minnesota Interagency Fire Center in Grand Rapids, Minnesota. “Conifers are undergoing a natural process as they start producing higher levels of starches and sugars for energy ahead of new growth. It’s a process that we commonly refer to as the spring dip.”

Spring dip is an annual event that sets in upon snowmelt. It appears as a reduction, or dip, of available foliage moisture content. During the spring dip, existing conifer needles produce the extra energy needed for new growth to emerge as conifers transition into photosynthesis. The timing of this pre-growth event, amid persistent dry conditions is contributing to this spring’s high fire danger as green-up continues to expand.

Verdegan says that conifers are noticeably more prone to wildfires reaching into the crown layer during the spring dip. The extra energy resources also produce additional fuel for a wildfire that can result in larger fires. The spring dip is dependent on the length of green-up conditions and can continue well into the middle part of June.