Freezing Fog and Low Clouds over Western Colorado

A ridge of high pressure moved into the desert southwest in the wake of a strong winter storm system that impacted the region last weekend.  Strong low level inversions beneath the ridge and melting snow cover increased the potential for an extended period of low clouds and freezing fog.  The MODIS Nighttime Micropyhsics product valid at 0501 UTC November 29, 2013 showed low clouds and possible areas of freezing fog along the I-70 corridor over and west of Grand Junction.  Observations at Grand Junction verified IFR low clouds at 900′ with visibilities above 6 miles.  The following VIIRS Nighttime Microphysics product at 0904 UTC November 29, 2013 showed low clouds and freezing fog expanding eastward into the Colorado, Gunnison, and Uncompahgre River Basins and the Grande Valley south of Grand Junction.  Visibilities have been significantly reduced to 1/4 mile at Montrose and farther south at Cortez.  The ceiling at Montrose is 200′ with visibility at 3/4 mile.  The nighttime microphysics product shows exceptional detail within the narrow valleys along Roan Creek to the northeast of Grand Junction.  Notice the fog and low cloud deck is very close to Rifle at 0904 UTC but the observation still suggests clear skies.  31 minutes later at 0935 UTC  the observation at Rifle dropped to LIFR at 400′ however visibilities remained at or above 6 miles.

MODIS NT Microphysics product valid at 0501 UTC November 29, 2013.

MODIS NT Microphysics product valid at 0501 UTC November 29, 2013.

VIIRS NT Microphysics product valid at 0904 UTC November 29, 2013.

VIIRS NT Microphysics product valid at 0904 UTC November 29, 2013.

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