Fire Weather Today Through Wednesday

Heat. It really comes down to that one word. Temperatures are going to be excessively hot over the next 72 hours which will push our fire danger up to correspondingly high levels as well. 

Today's maximum temperature, minimum RH, and wind speed/direction are below. Wind speeds will be on the light side over western SD where the driest conditions exist today. This will prevent us from reaching Red Flag Criteria. Southcentral SD has the highest winds speeds but higher dew points as well leading to higher minimum RH values. The other thing missing from this forecast is the thunderstorm activity over central/northern/eastern SD today. There are some wetting rains mixed in but there has been a LOT of lightning. I fully expect new starts from this activity. Additionally, a few storms are likely over the higher elevations of the Black Hills today and I don't expect much rain to come from those storms. 

Let's examine tomorrow's maximum temperature, minimum RH, and wind speed/direction (below). A very similar situation is in store but although thunderstorms are not expected. Once again, light(ish) winds will prevent the issuance of Red Flag Warnings. 

Now for Wednesday's maximum temperature, minimum RH, and wind speed/direction (below). A cold front will move through the state later on Wednesday, hence the shift in winds you see below. Typically wind speeds increase along the front so it wouldn't surprise me to see some local critical fire weather conditions. This would most likely be across northern/northwestern SD where winds speeds will be highest during peak heating.

Regardless of wind, the extreme heat will definitely increase the evaporative demand thus reducing fuel moisture. The Hot-Dry-Windy Index is a good measure for this. The charts below are the probability of exceeding the 90th HDW percentile. At least a few portions of SD will have a good shot at reaching that percentile each of the next 3 days. 

Once again, the lack of wind is really helping to stabilize a situation that could be exceptionally bad for wildfires. Regardless, conditions still look pretty nasty. And for a bonus image, regional ERCs are shown below. Most stations in SD are reporting higher than average ERCs with northcentral SD seeing record high ERCs. The fuels will burn if ignited.