Dry conditions around the area

It's been a while since we've seen our last precipitation event across much of South Dakota. Most areas haven't seen 0.10" of rain or snow-water equivalent in over two weeks. Precipitation totals for the past 14 days are found below.

There are plenty of dry swaths across the state and we are not expecting a major precipitation event until after the Christmas holiday (and by the way we could see a high-impact winter storm in the 12/26 - 12/27 time frame). So why does this matter?

The fine fuels are cured this time of the year and so the only way they will resist fire spread is if they are wet from precipitation. And you guessed it, if we don't have precipitation (or at least high humidity) those fuels will continue to dry. Find a warm day with relatively low RHs and a nice breeze and the stage is set for large fire growth across the prairies.

On December 17th, this exact scenario played out near Fairburn, SD where a 45 acre fire occurred. Interestingly, a new tool called the HDW index predicted that the 17th would have higher fire potential. The HDW looks at vapor pressure deficit (and measure of dryness) and wind speeds to calculate a value. This value is the compared to the climatological HDW for that day. If you start to get above the 90th percentile, you are getting closer to a historically warm/dry/windy day. Combine that dry fuels and you get good fire growth conditions. Below is the HDW forecast for today with the previous 6 days of HDW values and an ensemble forecast for the next 7 days. Tomorrow could be another one of those high fire danger days. My concern level is still relatively low because the warm/dry conditions will precede the windy conditions but it is something we need to pay attention to.

You can find real-time HDW data here: https://eamcweb3.usfs.msu.edu/HDW/index.html