Winter has finally arrived....I think

So after weeks for 15+ degree weather we have finally had below zero temperatures and SNOW!!! Our first snow fall was amazing...big white flakes that fell so slowly just as it started to get dark out. You know the kind when it gets so quite outside and you feel like you're in a winter wonderland? It was beautiful. Here are some pics I stole from Melissa....my mother finally took her camera back from me:-(
Since then...we have had a few other snow falls but today all the snow is gone:-( It has gone back up to +7 degrees...what is going on?