Wildland potential fire outlook for winter 2017-18
The National Significant Wildland Fire Potential Outlook is intended as a decision support tool for wildland fire managers, providing an assessment of current weather and fuel conditions and how these will evolve in the next four months. The objective is to assist fire managers in making proactive decisions that will improve protection of life, property and natural resources, increase fire fighter safety and effectiveness, and reduce firefighting costs.
The significant wildland fire potential forecasts included in the National Significant Wildland Fire Potential Outlook represent the cumulative forecasts of the ten Geographic Area Predictive Services units and the National Predictive Services unit.
For the months of December thru March this National Outlook highlights much of the southern portions of Kansas as having above-normal significant large fire potential (Figure 1). Above-normal potential means a greater-than-usual likelihood that significant wildland fires will occur. Significant wildland fires are those requiring mobilization of resources beyond the typical local response area.
Figure 1. Significant wildland fire risk. Graph produced by Predictive Service, National Interagency Fire Center.
Chip Redmond, meteorologist with the K-State Mesonet and an Incident meteorologist, helps explain the concern, “Some parts of Kansas, especially the south central and southwest areas, saw above-normal moisture during the growing season, with many reports of large to significant fuel loads as a result. Areas south of US-50 have seen considerable drying during the previous month with many locations exceeding 60 days without a wetting rain. This, combined with recent above-normal temperatures, sunny skies, and breezy winds, are rapidly depleting any remnant moisture.” According to Redmond, “while this is not unusual for this time of year, any deficit developed will be very difficult to overcome without a period of above-normal moisture between now and March. It is our desire to make interested parties aware that these elements are lining up for the upcoming season, even if we do obtain a period of above-normal precipitation in the meantime. Regardless, with recent forecasts of mid-to-long range dryness continuing, we are setting the stage for some large fires in Kansas with heavy fuel loading and flash-type drought.”
Growing Season Precipitation
Precipitation received during the growing season, April to September, is a determining factor for the upcoming fire season (Figure 2). The previous two years received above-normal precipitation (2016:124% and 2015:105% compared to normal statewide) which contributed to large fires the following winters. However, in 2017, the growing season was characterized by slightly below-normal precipitation (98% of normal) overall. This is partly due to the dry months of June and September. Despite those deficits, April (174%) and May (111%) were significantly wetter-than-normal. Therefore, despite a marginally drier period in 2017, the timing of the moisture was critical for supplying ample grass and fuel growth the remainder of the period.
Figure 2. Percent of normal precipitation for April-September, 2017.
This increased fuel load is a large concern for the next few months which are typically the driest period of the year for Kansas. With any strong system, the potential exists for large fires similar to what we have seen the last two years.
Current and Future Weather
Much of Kansas began to dry out in September. Some places in western Kansas haven’t received even 0.1 inch of rain in over 60 days. Above-normal temperatures for much of November combined with gusty winds have caused surface moisture to rapidly evaporate. As a result, drought conditions are beginning to expand across much of Kansas. According to the Drought Monitor, nearly half the state is considered “D0 – Abnormally Dry” and another 15% in “D1 – Moderate Drought”.
Long-term forecasts suggest the dry period will continue through much of December (Figure 3). Fortunately, temperatures should be more seasonal (cooler) the remainder of the month. Unfortunately, the upcoming weather pattern is also associated with periods of very windy conditions associated with numerous dry, cold fronts.
Figure 3. One month (December) and 3-month (Dec.-Feb.) temperature and precipitation outlooks issued by the Climate Prediction Center. Source: www.cpc.ncep.noaa.gov
Beyond December, trends are bit more difficult to discern. The January through March period is typically very dry in Kansas, averaging only 3.85 inches of total precipitation statewide. Any precipitation that does occur will only have short-term impacts on the dried out fuels until the arrival of spring rains. The biggest concern during the next few months will be the occurrence of very warm days. These are typically associated with very dry air and high winds in advance of a strong storm system. Kansas’ largest wildfires are usually dependent on the shifting winds and the lack of moisture associated with these systems. Normally, Kansas will see several of these systems before one can eventually tap into the Gulf moisture and provide much needed rainfall.
Finally, the influence of precipitation type is also important. Snowfall can often knock down or flatten the standing grasses. This removes the vertical fuel load and can significantly decrease fire behavior. A lack of snowfall through December will continue to make these grasses available and lead to suppression difficulties until a snowfall event occurs.
Jason Hartman, Fire Protection Specialist, Kansas Forestry
Christopher “Chip” Redmond, Weather Data Library
Mary Knapp, Weather Data Library