Impending hot weather and fire danger

A large upper level ridge will set up over the Rocky Mountain Region in the near term and this will bring above average temperatures to large swaths of the central and northern Great Plains as well as the Rocky Mountains.

Generally, above average temperatures in mid-July would concern me as a fire meteorologist. But conditions are still not favorable for large fire growth. To get large wildfires across SD, including the Black Hills, during July we need to have several elements in place:

1. Drought conditions (or long-tern precipitation deficits). Drought leads to dry soils and the desiccation of the larger fuel classes. However, we do not have drought or even abnormally dry conditions anywhere across the state. Below are the 120-day departure from average precipitation and the current US Drought Monitor for South Dakota. 

2. Short-term precipitation deficits. Short-term precipitation deficits lead to the drying of the fine fuels and the needle cast/litter on the forest floor. These are the main contributing factors to large fire spread. But we do not have any precipitation deficits in the short term. In fact, flooding has been more of a concern. The top figure shows the observed departure from average precipitation over the past 30 days and the bottom figure shows the radar-derived 30-day precipitation total for the state.

3. Hot temperatures. A continued period of hot temperatures is required to get large wildfire growth during the summer as it contributes to stress and an earlier drying of the fine fuels. Recently, we've seen below average temperatures (top figure) along with those above average precipitation totals. But, as stated previously, we are expecting hot temperatures in the near future (bottom figure). 

4. Available fuels. To get big wildfires, you need fuels that are sufficiently dry to carry wildfire. And this year are fuels continue to be extremely green. The VegDRI product is a good tool to use to determine overall fuel dryness and this year it is showing exceptionally green fuels (figure below). The yellow "pre-drought stress" vegetation condition over portions of western SD is more likely due to a big sweet clover crop that appears yellow to remote sensing tools. The fuels are just not dry enough to support wildfire growth. 

Summary: In short, we are still looking at below average large wildfire potential through the month of July. If the hot temperatures continue this month AND we see below-average precipitation, the wildfire potential might start to climb during August. But the long-term forecasts do not favor that scenario. So get outside, enjoy the hot weather, and always remember to be fire safe regardless of environmental conditions.