We wish could better quantify the risk of this event to Saint Louis, but the authorities have not released enough data for us to make a good assessment. The data they have released indicates that the WIPP site was still releasing approximately 6,667 Becquerel of Pu239 + Am241 every minute, based on an estimated 20,000 cubic meter per minute mine ventilation exhaust rate.
Given that there will likely be Plutonium present, and that rain/ice/snow fall may concentrate it, we believe it wise to take prudent risk avoidance measures. For us, that means avoiding travel, staying indoors, and using HEPA filters. Precipitation allowing, we will attempt to take surface samples.
We will have our LIVE INDOOR AND OUTDOOR RADIATION MONITORS up and running. However, we think it unlikely that we will be able to identify a noticeable spike from Plutonium, even if it is present. We may have had such a detection on 2/15, but that Plutonium plume was much larger than what is expected to arrive this weekend. But in anycase, better safe than sorry.
Sources:TIME ZERO Plutonium Cloud was 330 MILLION Becquerels in Size; DOE Claims Current Releases Safe--BUT