[12Z GFS 10-day forecast map for 500 millibar height anomalies (blues=low pressure trough, oranges=high pressure ridge); map courtesy "tropicaltidbits.com", NOAA]
Despite the chill for the past two days in the I-95 corridor, so far the month of April has actually been warmer-than-normal in DC (+3.2° at Dulles Airport), Philly (+2.1°) and at Central Park (+1.5°) in New York City. In addition, tomorrow will feature a dramatic warm up throughout the Mid-Atlantic region and it should stay relatively mild though much of next week. However, on a longer-term basis, it appears that we are definitely not done with the colder-than-normal air yet as there will be a pattern change later in the month.
A deep trough of low pressure (blue area on forecast map above) will form in the eastern US in 10 days or so according to the most recent GFS computer forecast model run and this will produce a pattern similar to that of much of the winter season which generated below-normal temperatures in the eastern part of the nation while much of the western US is relatively warm. In fact, going a few days farther into the future, the latest GFS model forecast for 14 days from now (below) features a blob of colder-than-normal temperatures (blue) in the Northeast US with much of the interior western US warmer-than-normal (oranges).
Enjoy the warmth that returns tomorrow and lasts well into next week as April can be a cruel month and change on a dime in the Northeast US.
[12Z GFS 14-day forecast map for 2-meter temperature anomalies (blues=colder-than-normal, oranges=warmer-than-normal); map courtesy "tropicaltidbits.com", NOAA]