MODIS post-snow observations…

After a very light snowfall across the area yesterday and last night, I was

Figure 1. MODIS Vis Imagery from 1646Z 13th January 2012. Red arrows point to red ovals and areas of known snowdepth. Yellow areas point to unidentified linear features.

interested to see if the MODIS vis imagery would show any lingering snow on the ground this morning. Indeed, some snow did show up especially on the 250m resolution vis imagery mainly across portions of Lauderdale and Colbert Counties (Figure 1). Two relatively broad swaths of snow show up across southern Lauderdale County in the southward “dip” in the Tennessee River around the Okland and Florence areas. Part of that same swath shows up in northern Colbert and Lawrence Counties from around Cherokee to Town Creek.  For reference, the cooperative observer at Muscle Shoals (which is just east of Sheffield in the map) just reported 0.1″ of snowfall and a trace depth this morning at 7 am CST.

Figure 2. MODIS Vis Imagery from 1646Z 13th January 2012, overlaid with state roads. Red arrows point to red ovals and areas of known snowdepth. Yellow areas point to unidentified linear features.

A CoCoRaHS observer about 7 miles SW of Cloverdale, AL, and within the heavier band in Lauderdale reported 0.3 inches.  What was rather peculiar were a couple of straight narrow lines that showed up in the imagery just south of the larger bands of surface snow. These are indicated by the yellow lines. At first, I thought the northern one might be Highway 72, but this was likely not the case as shown in Figure 2. These bands do not show up in the GOES or lower resolution MODIS imagery (1 km or higher) and we could not match them up with any other surface feature. It’s possible that they are contrails, but didn’t quite have the typical look. Radar imagery from the afternoon between the hours of 3:20 to 4:39 pm CST shows a pair of convective snow showers with fairly high dBZ (max ~47 in VCP 31) moving across the area, including the locations with the narrow unidentified lines.

Figure 3. Radar Reflectivity Loop (KHTX - Hytop, AL) between 3:20 to 4:39 pm CST January 13th, 2012.

2 thoughts on “MODIS post-snow observations…

  1. It might be interesting to also look at the MODIS false color product to see if that is snow on the ground and also to see if the false color product is sensitive enough to pick up such a light amount of snowfall.

  2. Hey Brad, yes the vis loop from GOES also showed the broad area of snow on the ground that melted during the day as temperatures rose above freezing. I did look at the false color product, and unfortunately, it was not as definitive with the light snowfall.

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