UPPER LEVEL ANALYSIS

Next, the MD says there's a fairly deep dry layer below 700 mb on the Albany upper air sounding.  The image below of the Albany sounding on January 8 at 00Z shows the temperature and dewpoint going far apart at 700 mb and remaining apart down to the surface. This is a sure sign that any precipitation would initially evaporate before reaching the ground.  A reexamination of the 850 mb winds from the SPC archives indicates strong winds advecting moisture into the area which will saturate this layer within a couple hours, along with the falling precipitation.


This is the 00Z sounding from January 8, 2007 which shows dry air below 700 mb.  This causes precipitation to evaporate
before it reaches the ground, courtesy of Plymouth State Weather Center.

To further support the notion that precipitation in the MD area will soon reach the ground, let's look at some observations to the south, where the precipitation is coming from.  These meteograms, courtesy of Plymouth State, from Binghamton on January 7 and 8 show precipitation falling from approximately 6,000 ft. shortly after the ceilings were 10,000 ft., like the MD states.  Also,  Williamsport's meteogram shows rain falling from 5,000 ft. which is the same level as the 850 mb winds, transporting moisture into the area.  The image below, showing temperature advection and winds at 850 mb, indicates winds as high as 40 knots just to the south, meaning the precipitation will move into the area at about that speed.  Also, the warm advection means that the snow may melt on the way to the ground, but it may refreeze on contact, due to cold surface temperatures.


This is an image of 850 mb temperature advection, height, temperature and wind from 0100Z on January 8, 2007 which shows the warmer air and its 
speed moving into northern New York and northern New England, courtesy of SPC's Daily Archive Directory.


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