Sunday, February 17, 2013

Feb 17, 2013: Rare Lake Effect Snow Showers Impacting Region This Afternoon

After an arctic front passage, the Great Lakes region often "clears up stormy", which refers to the development of Lake Effect snow showers.   Very cold air and high winds moving over much warmer lake water (as long as the lake surface remains unfrozen) causes warming and moistening of the air layer just above the lakes.   This destabilizes the air mass and causes it to convect (overturn), leading to showers of snow along and downwind of the lee shores. 

Typically, these lake effect bands - which are quite narrow but can extend over 100 miles downwind - fizzle by the time they approach the Mason Dixon Line.  But this afternoon, the arctic air mass is unstable enough...the wind trajectory is just right...and an upper air disturbance is helping to sustain uplift of air...allowing lake effect snow squalls to extend all the way into central MD and the Baltimore metro region.   The skies are very scenic, with whitish streaks of snow falling from beneath deep cumulus clouds.  Although the air beneath the cloud bases is very dry, some of these flakes are surviving to the surface.   No one should receive any more than a dusting from these snow showers.  Here is how the situation looks on weather radar - presenting as a very unique signature:

So enjoy a little taste of Lake Effect snow this afternoon!

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