How can it be so cold when yesterday was so warmSWAG QUEEN

What made the weather in the East change so rapidly from warm to cold? There were a number of things in play for this rapid drop in temperatures. The rapid change in temperature has a lot to do with the jet stream. The jet stream divides two air masses: the trough, the southward dip in the jet stream, and the ridge, northward bulge in the jet stream. A trough generally brings chilly, or unsettled, weather and a ridge generally brings dry weather.
In this week's case, there was a really big trough. When there is big trough that means the cold air over the north dipped well to the south. In turn, very warm air was forced to the north ahead of the front. The jet stream usually moves west to east. In this case, the jet stream was oriented south to north instead of west to east. There was a huge temperature difference across the front from west to east, which is a bit unusual. To make the cold weather even more extreme, rain fell behind the front, which chilled the air with evaporation cooling. That made the transition to cold air that much more abrupt for the east.

Drastically Colder in the NortheastDrastically Colder in the Northeast The sunny and warm weather that encompassed much of the East the past several days has been erased by...

RT - @_Rogue_Wave: Thermometer here at Amicalola Falls this morning! http://pic.twitter.com/A4DExRUA // yes, the change was quite abrupt this morning.Steve Milone FOX 5

2 days ago, I was in shorts. Today, it's snowing. Not asking for warm weather year round, Cleveland, but a little consistency would be nice.Ben Yabrow

Lol at the people wearing t-shirts cuz they thought it was gonna be warm like yesterday. #welcometocanadaKellie Foster

I wish I could bring the warm weather back to New York Lorena Bobbitt

Don't know why I thought just a rain coat would be warm enough. Maybe because yesterday was in the 60sEmily

we was just feeling good, now we back freezing !im'thatGIRL..

It was warm and sunny yesterday #whathappened? http://pic.twitter.com/ZjF0gvzGJessica Greene

It was warm and 18 degrees yesterday. Right now it's cold, 4 and snowing. #OttawaAhmed Dirie

Morning #NYC! Cold day! Bom dia galera! Aqui ta friooooooo http://pic.twitter.com/DSoz9100David Luiz

Wake up Arkansas!! It's cold out there. Be sure to grab a coat before heading to class today! http://pic.twitter.com/W4D04Vy1Razorback Yearbook