RGB NT Micro Identifies IFR Stratus in Alaska’s Copper River Basin

In the early morning hours of Wednesday, January 29th a deck of low stratus clouds developed over the Copper River Basin in Alaska.  The RGB Night-Time Microphysics product derived from SNPP VIIRS instrument at 1321UTC (4:21am local Alaska time) is shown in the following screen capture from the National Weather Service’s AWIPS workstation at WFO Fairbanks, Alaska.   This view is zoomed into the southern portion of mainland Alaska; the Copper River Basin is northeast of Anchorage and includes the community of Gulkana.  The 1253UTC METAR observation from Gulkana indicated an overcast ceiling of 500ft above ground, with seven miles of horizontal visibility.  The RGB NT Micro depicts the stratus deck with a gray-yellow color, and one can see the low clouds confined by the higher terrain and covering the broad Cooper River Basin as well as following the more narrow Copper River itself as it flows southeast of Gulkana and eventually into the Gulf of Alaska.

Copper Basin annotated

A comparison of the RGB NT Micro product with different VIIRS products from the same SNPP pass is presented in the following 4-panel screen capture.  The RGB NT Micro is in the upper-left, the Day-Night Band is in the upper-right, the 11.45 micron IR is in the lower-right, and the traditional channel differencing fog product is in the lower-left.  The deck of stratus clouds over the Copper River Basin is also evident in the longwave IR imagery and the fog product.  The clouds are thin enough that the city lights of are evident through the cloud layer in the Day-Night Band.  In this example, it appears that the stratus deck is most evident in the RGB NT Micro and the fog product, and least evident in the Day-Night Band.

Copper Basin 4-Panel

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