On this date one year ago, the high temperature reached 96 degrees in Philadelphia, 97 degrees in Washington, D.C. and 97 degrees at Central Park in New York City in what turned out to be the hottest week of the summer. What a difference a year makes!
A chilly air mass for this time of year moved late yesterday from the Upper Midwest/Great Lakes region to the Mid-Atlantic and indeed there record lows were tied or broken this morning in the following nearby locations (new record, year of previous record):
Pittsburgh, PA (52, 1970) Dubois, PA (49, 2003) Dulles, VA (55, 1976)
In addition to these nearby locations, record lows were tied or broken this morning all the way into the Deep South in such cities as Atlanta, GA; Pensacola, FL; Jackson, KY; Mobile, AL and Vicksburg, MS. Yesterday morning saw numerous records tied or broken throughout the middle part of the country:
Temperatures late tonight/early tomorrow should drop into the 50’s in the suburbs of Philly and New York City and into the 40’s across higher terrain locations in upstate Pennsylvania (e.g. Poconos).
The air mass creating this chill across the eastern half of the nation had its origins in northern Canada several days ago. In fact, using computer forecast models, NOAA’s Air Resources Laboratory can calculate the approximate trajectory of an air mass and the map shown above indeed shows that the origin region of the air mass now entrenched in the Mid-Atlantic region is just north of the Arctic Circle. This NOAA model called "HYSPLIT" is a complete system for computing simple air parcel trajectories.