Fog forecasting can often be challenging in parts of the Tennessee Valley, especially this time of year. The development of fog often takes place in the relatively narrow valleys of northeastern Alabama and southern middle Tennessee, when cool air drainage off the tops of nearby ridges and the Cumberland pleatau settles in the valleys. The early detection of this fog can be pivotal is assessing its eventual intensity and coverage. The MODIS-GOES hybrid 11um-3.9 product early yesterday morning showed the usefulness of the MODIS imagery especially in comparison to the coarser resolution GOES imagery. The image below is the color enhanced 11um-3.9 product, but was the GOES image valid at 0645Z.
The next image is the MODIS image taken valid just 16 minutes later at 0701Z.
Notice the much finer detail of the MODIS imagery. Also notice the indication of fog development in the valleys of northeastern Alabama and southern middle Tennessee, in the Tennessee River valley and Paint Rock River valleys of Jackson County in particular. This heightened forecaster situational awareness and suggested that fog development was likely further southward in the valley of Jackon County, potentially affecting the urban area of Scottsboro and the Hwy 72 corridor. The fog did develop that morning and was intense enough to cause visibilities to drop below 1/4 sm at Scottsboro. A dense fog advisory was eventually issued. Below is a visible image shortly after sunrise, showing the fog development in northeastern Alabama stretching northeastward through the Sequatchie Valley of Tennessee.
This was a situation where the MODIS-GOES hybrid product helped to enhance forecaster situational awareness and confidence in fog development, and lead to improvement of forecast products.