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. 

We remain dry but rains have helped

We've recently seen a bit of precipitation across the state, generally ranging from 0.5 - 1.5" over the past 7 days. This has obviously helped the cause as we have been so incredibly dry over the past few months, especially over eastern and central SD. 

But if we look at the 30-day percent of average precipitation, you can see that the conditions remains very dry relative to historical norms. 

We have also been seeing some hot temperatures over the past month which further dries the soils and the fuels on the landscape. Temperatures over the past 30 days have been from 3-7 degrees above average--pretty incredible over the period of a month. 

The vegetation is really becoming drought-stressed due to the combination of heat and little precipitation. The VegDRI product shows this. Top chart is from a month ago, bottom chart is from this week. The situation is getting worse quickly. 

Ok, so things look pretty bad. Has the recent rain helped at all? In short, yes. The rain has at least dampened the fuels so that they are not as receptive to ignitions or to carrying fire. This is especially true for the 1- to 10-hr fuels (needles and grass up to finger-sized sticks). The recent trends in Energy Release Components (ERCs) have demonstrated this. I've shown Baker Park RAWS and Red Canyon RAWS as examples. Whereas they were near or at record highs a few weeks ago, the ERCs are now trending lower than average. But remember, these stations are in the Black Hills which HAVE been getting decent rains--the prairies haven't been getting those same rains. 

So, at least in the Black Hills, conditions are in a holding pattern. We've gotten enough rain to limited the fire threat in the near term. But the prairies are made almost exclusively of fine fuels or those 1-hr fuels. These fuels only take a day or two to fully dry and be conducive to carrying fire. In short, they respond more to the day-to-day weather conditions. If we get a hot/dry/windy day, they will be ready to burn. 

What scares me is the forecast going out towards the latter half of July. There are some strong hints that more hot weather and above average temperatures are on the way. Here are the CPC forecasts from the 8-14 day timeframe and the 3-4 week timeframe. 

That's a tough outlook for the latter half of the month. There is *high* confidence of these warm and dry conditions as well. 

I'm no plant phenology expert, but from my understanding the herbaceous fuels on the landscape really can't pick up and use the moisture that we've gotten over the past week. They've already crossed the threshold: they are seeded out and curing for the season. So the precipitation really won't help them out too much. Add some heat and additional dry weather and it creates a situation where the fire potential will likely increase going into August. 

The big fire out by Pickstown over the 4th of July weekend goes to show that the fuels in the Missouri River breaks will readily carry fire. The eastern red cedar had no problem torching out. Remember that big fires are not limited to the Black Hills here in SD--we have a lot of fuel on the landscape and this might be the year where it burns.