A Frontal Passage to Remember

Wow!  What a difference an hour makes!  Yesterday afternoon, Harrisburg, PA reached 69ºF at shortly past 2 pm for the daily max temp.  Then, a mere 5 hours later, the mercury fell to 35ºF with snow, sleet, and rain for the daily min!  Now a 34ºF daily range isn't all that extraordinary; however, the manner in which it occurred is.  I was driving to Columbia, PA with my lovely bride for our annual sauerkraut dinner and experienced what is called a "gust front" or in the meteorological community properly termed an Outflow Boundary.  Study the graphic below:

As it's been so dry in recent times, the gusty winds associated with the deep forced convection from the new air mass regime, caused vast amounts of dust and debris to be swept airborne.  As we traveled I-83 S towards York, there were times up in the distance that I commented to my wife, "Look at that smoke up ahead!"  But I quickly realized that what I first perceived as smoke was actually dust and debris blown 100's of feet into the air.  Also observed were numerous vorticities or "mini-swirls" easily observed by the downed leaves and dusty fields and unpaved parking areas.  It was actually very impressive!  A few of these gusts within the gust front pushed the car with alarming force.  Then, once we reached US-30 E, we actually pulled away from the leading edge of gust front, reached our destination in Columbia, only to experience the turbulence of the extreme gusty winds once again!  KMDT had a gust of 52 mph yesterday.  I believe in my travels during the passage of the gust front higher gusts we observed.  It was a spectacular cold frontal passage and one that was well advertised by mother nature.  Look at what the storm system did in terms of laying down a blanket of white with the invading cold air from O Canada!

Here was the surface map as the front passed through PA...note the 2nd front just to the north of Michigan; you will note its arrival with the ringing of Sunday's church bells and you and your neighbor's wind chimes...that is if they don't get blown away!

And although it has been enjoyably warm for this entire autumn season, change is certainly on the way!  While North America has been "basking" so to speak, most of the earth away from the polar regions has been quite chilly for the month of November to this point; take a look...

China and North America is warm; Europe, India, South America is cool.  Asia is brutally cold!  Although O Canada is slighlty behind its snow cover for this time of year, Asia is not.  The snow cover is at a record max for this point in the cold season.  Take a look at the snow/ice coverage valid yesterday from a northern hemispheric view...

And given the longer term upper air progs (which I will not show at this time to keep this at a readable length), any cross polar flow will flood North America with cold air.  So I do hope y'all enjoyed this borrowed time of warmth these last several weeks because we are about to embark on what I believe could be a real eye-opening December.  The map below shows the mid-levels of the atmosphere with lower pressures lying under higher pressures to the north.  In meteorological terms in the eastern part of the continent, that is referred to as "blocking" which generally tends to create slow moving storm systems and often snowier than normal conditions.  This map is just that...

With the fact that air flows from regions of higher pressures to regions of lower pressures and given the time necessary for atmospheric change to take place, by January, the long term US model shows January to be a very cold month...ouch!

OK...gotta run.  But with all of this wind about to grace our presence, I will leave you with this classic remake of a wonderful American folk story.  It's a long song, but well worth the watch/listen...

Enjoy your Thanksgiving week and today's Feast of Christ The King...

Smitty

AA:  First off, thanks for all the obs yesterday my secret wx observers across the greater KMDT area!  Greatly appreciated and shared with our clientele and comrades alike whilst in Columbia last evening...as for the AA version y'all have grown to expect; very windy today with slacking winds by Tuesday.  But much colder than recent weeks...here is one last map...the temp anomalies averaged over the next 5 days...it is quite a change!