Critical Fire Weather Today

Today is a VERY interesting day from a fire weather perspective. There are a variety of issues that need to be discussed including: drought, prior precipitation, fuels, temperature, wind, RH, and thunderstorms (wind and lightning). 

Drought:

Drought conditions vary across the state but summertime wildfire activity is highly correlated to drought conditions. Here is the current USDM.

Prior precipitation:

Wildfire activity is also well-correlated to short-term precipitation deficits. Over the past 7 days, many areas have not received any precipitation across the state. Below is a map of the accumulated precipitation over the past week. 

Fuels:

The drought and lack of recent precipitation has led to a quick drying of the fuels on the landscape. Below you will see the current (as of 1300 MDT on 6/28) ERC chart for the region. 

From a "preconditioning" standpoint, all of the things are in place in order to get a large wildfire. The one thing holding us back in the lack of curing in the fuels. However, areas of central SD as well as those areas south of I-90 are seeing the herbaceous fuels undergoing a quick dry down and most areas will be receptive to ignitions and fire spread. It's not September dry but it is definitely drying down. 

Temperature:

If you haven't yet heard, it is going to be very hot today. High temperatures will be in the 90s and 100s in most areas. 

RH:

Along with those hot temperatures, the relative humidity will be critically low (note the color scale on the bottom). 

Wind:

Breezy southerly winds are expected over eastern SD and breezy southwesterly winds are expected over western SD through the day (see wind barbs in the RH figure above for wind direction). Winds gusts are shown below, again see the color scale at the bottom. 

Thunderstorms:

To add insult to injury, we are expected high-based thunderstorms this afternoon and evening which could result in scattered dry lightning. The images below show a weather model depiction of the radar reflectivity and associated with gusts today at 1800 MDT. 

Wind gusts from thunderstorms could range from 55-75 mph in an environment characterized by ~2000 J/kg of downdraft CAPE. That will not only be a threat to on-the-ground firefighting resources, but to aerial resources as well. 

It's an interesting day out there. Stay safe.