Recently, three NWS offices participated in an assessment of several SPoRT Land Information System (LIS) soil moisture products for applicability to drought monitoring and flood threat applications. Currently, two soil temperature products are being sent to the same WFOs (Houston, Huntsville, and Raleigh) in an initial testbed phase during this winter. These soil temperature variables are 3-km average surface skin temperature and 0-10 cm soil temperature. Due to the recent very cold air temperatures, both skin and 0-10 cm soil temperatures were quite cold across the Tennessee Valley. However, temperatures were a little warmer further to the south over portions of the lower Mississippi Valley and the Gulf Coastal Plan region. Nevertheless, the SPoRT LIS still indicated that soil skin temperatures were cold enough for the potential for freezing precipitation to accumulate on surfaces. Take a look at this image of combined SPoRT LIS average skin surface temperature and regional radar data from earlier this morning (Figure 1).
Since the radar data are displayed on top of the SPoRT LIS soil temperatures, the soil temperature scale does not show in AWIPS II…unfortunately. However, the white colors indicate temps ranging from -1C to +1C. The cyan colors found generally along coastal Louisiana and Texas and portions of Florida, are above freezing, while the deeper blues represent values well below freezing. Notice that average skin surface temperatures according to the SPoRT LIS across much of Mississippi were below freezing, despite temps at or above freezing in southern Mississippi (although the data latency should also be noted…the LIS data were valid at 09 UTC). Icy conditions with freezing rain were reported around portions of central and southern Mississippi with the precipitation that moved across the area. The Jackson NWS office had issued a Freezing Rain Advisory to address this winter weather threat.
Soil temperatures can be very difficult to come by, and forecasters often have to make assumptions about these values. Here, the value of the LIS data can be seen to address the threat for freezing precipitation accumulation in a winter weather event.