Ice Accumulations make for Treacherous Travel Conditions

Ice Accumulation February 12-13, 2008  Source: NWS

Tonight and tomorrow morning’s freezing rain will make for treacherous travel conditions across much of the region.  Although temperatures were slightly warmer today than they have been recently, surface temperatures are still near the critical freezing point in many spots.  The dry air will also cool due to evaporative cooling once the precipitation starts to fall overnight. The cold surface temperatures will allow the rain to freeze on contact in many spots.  That’s known as “freezing rain.”  Even the smallest accumulation of freezing rain on roads and power lines can create dangerous travel conditions and power outages. 

 

There have been several memorable ice storms in the Mid-Atlantic Region during the last 20 years.  Some will remember that during the evening rushour on Virginia’s Primary Election Day in February 2008, there was freezing rain that caused havoc on area roadways.  The Springfield Interchange in Northern Virginia became a virtual parking lot as road crews simply couldn’t treat the roadways amid rushour traffic.  It took hours for most commuters to get home that night and there were scores of accidents due to icy roads.

Also, on February 13-14, 2007, there was a significant accumulation of freezing rain and sleet across the Mid-Atlantic Region that made travel all but impossible on area roads.  There was an accumulation of 2.2” of primarily sleet at National Airport, with a glaze of ice covering most surfaces around the region.  Western and Northern suburbs saw a touch of snow, but this storm was generally sleet and freezing rain.  Finally, in January 1999 there was widespread accumulation of freezing rain across the DC Metro Region that led to significant power outages as windy conditions blew down ice-encrusted power lines and tree limbs.  It took several days to restore power and many people were stuck at home with schools and businesses closed. 

Tomorrow, temperatures are expected to rise during the day, causing the precipitation to change primarily to rain in the morning across the DC Metro Region before ending later in the day.  It’s safer, though, to stay off the roads regardless of the type of winter precipitation – snow, sleet and freezing rain are all very dangerous to travel in.  To read more about the difference between snow, sleet and freezing rain, check out my December 27 blog post.

Weather Quiz

Which city averages the most snow in a given winter ?

A.  Seattle, Washington

B.  Chicago, Illinois

C.  Washington, D.C.

D.  Denver, Colorado

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Answer to Weather Quiz question from January 2

True.  The last time it was below 0 in the Nation’s Capital was in January 1994.  The coldest average low temperature in Washington, D.C., is 28 degrees from January 12 to January 23.  To read more about the extreme January cold in 1994 and other more recent record cold waves, check out my recent blog post from January 4.

Early January Snow Can Be Devastating

"Blizzard of '96" snow totals   Courtesy: NWS

Today’s snowfall pales in comparison to the storm 19 years ago.  Beginning January 6 and spanning a total of three days, snowfall totals of 15” to 25” were common in the major 1996 winter storm along the DC-Baltimore corridor.  A total of 17.1” fell in the Nation’s Capital, with 26.6” at Baltimore measured at BWI-Marshall Airport, and 24.6” fell at Dulles Airport.  At the time, these totals made the storm the fourth largest on record for Washington, D.C.

The 1996 storm was particularly memorable for a few reasons.  First, a number of years had elapsed since the immediate DC-Baltimore Region saw a snowfall of this magnitude.  Also, residents who went to school in the DC Area may remember that the January 1996 storm was the first time many local school districts closed for at least a week due to snow.  The high volume of snow left roads and sidewalks impassible and made transportation all but impossible for several days after the storm.  (Although, many local school districts closed for a week in January 1994, after an ice storm and subsequent week of record cold, that was not because of a snow event.  See my recent column to read more about the record cold from January 1994.)

The 1996 snowstorm was a classic “Nor’Easter” – a coastal storm that developed along the U.S. Gulf Coast and tracked northeastward up the East Coast.  There was already ample cold air because of an area of high pressure that kept frigid air from Canada in place.  That allowed the storm’s prodigious amount of moisture to fall as pure snow, while winds blew primarily from the “Northeast.”  The predominant direction winds blow in are what gives a “Nor’Easter” its name. 

 

Moreover, during the days after this initial snowfall there was a minor snowfall on January 9, followed by a more significant snowfall on January 12 from another coastal storm that brought another 4” to 12” of additional snow across the Mid-Atlantic Region.  These three snowfalls in the span of a week helped make the 1995-1996 winter season one of the snowiest on record for the Nation’s Capital.

By comparison, today’s storm – that brought the region a few inches of light, powdery snow – was from an “Alberta Clipper.”  It is a fast moving area of low pressure that originated in the Canadian province of Alberta and typically moves Southeast across the Northeastern United States. What a Clipper lacks in moisture, it makes up for in wind and cold air.  A far cry from the historic storm 19 years ago, today’s Alberta Clipper generally brought 2” to 4” totals, with isolated pockets getting more than that. 

This fresh snow cover will help create ideal conditions for frigid weather the next few days.  High temperatures will remain in the 20s both tomorrow and Thursday.  Low temperatures will fall to the single digits and teens Wednesday night and Thursday night.  Temperatures are not likely to climb above freezing again until Friday.

Frigid Weather to Return this Week

January traditionally features outbreaks of extreme cold weather in the Mid-Atlantic Region.  Longtime Washingtonians will remember January 1994 – the last time it was below 0!  It was -4 on January 19 and the high of 8 on January 19, 1994 was the second lowest high temperature on record in Washington, D.C.  January 1994 was so cold that there were four days where temperatures didn’t even reach 20 degrees at National Airport – the official weather reporting site for Washington, D.C. 

Then, in January 2004, there was a six-day stretch of below freezing temperatures.  Also, area residents likely remember how cold it was before and after Inauguration Day in 2009.  During that three-day stretch in 2009, ending January 17, the highest the temperature got was 29 degrees.

Last winter was especially cold and snowy for the Mid-Atlantic Region.  There were seven days in January 2014 when temperatures failed to get above freezing.  In fact, the high temperature last January 19 was only 19 degrees – less extreme than in 1994, but significantly below the daily average high of 43.

Such extreme cold can be largely attributed to the position of the jet stream – a river of air in the atmosphere that helps regulate the weather by guiding storm track and movement of air masses.  When the jet stream dives south from Canada during the winter months in the Eastern United States it helps drives very cold air southward.  This affects many of the populated areas of the Central and Eastern United States. 

Hopefully, you have been able to enjoy the relatively mild weather in the Mid-Atlantic Region today since the weather is going to take a dramatic change this week with the winter’s first sustained stretch of cold weather.  High temperatures will likely remain below 30 degrees on Wednesday and Thursday for much of the DC Metro Region.