The time has come for my forecast numbers to be released, and etched in history so that come March we may revisit them and chuckle at either A. How correct they are, or B. How incredibly wrong I was in trying to predict one of the most complex systems in physical science.

First and foremost, my winter forecast for the area around Southeastern Pennsylvania!


If you read part 3 of my winter forecast, you noticed that I think that the predominant storm path will come from the south and up the east coast.  My snow mongering friends will hear that and get really excited..but as Lee Corso says..Not so fast my friend!

It is true that some of our strongest winter storms have taken this path up the coast, and with the anomalously warm water temperatures, a fantastic baroclinic zone will set up (an area with a large temperature gradient), which is one of the ingredients for explosive cyclogenesis (storm creation).  Typically with these storms, a battle line is set up where the warm ocean air and the cool continental air collide and we see a changeover to snow/rain.  Often this line is difficult to predict, and can move as the storm progresses.  My forecast is based on the assumption that the line will set up somewhere between Philadelphia and Allentown for almost all the storms while the Lehigh Valley remains all snow during most events.

Forecast Numbers

2012-13 Forecast
Last Year
West Chester
Atlantic City


What is Needed for the Forecast to Come to Fruition?

For my forecast to end up being correct, I need some help from Mother Nature.  First off, a slight El Nino must remain in place to give the proper storm path.  Although I mentioned that there is little correlation to precipitation with El Nino, there is some evidence that shows that snowfall is increased during years with a slight to moderate El Nino.  It is possible to have increased snowfall but have a decrease in precipitation, but that is a subject for a different day.  In addition to the slight El Nino, there needs to be some blocking downstream which implies a negative NAO.  This blocking will help keep storms close enough to the coast as well as push them through the baroclinic zone so that they can strengthen.  Both of these ingredients are crucial for a snowy winter in the Lehigh Valley.  Finally, the AO needs to be negative to allow some of that very cold air to seep down from the arctic.

If all of this happens, then I think my forecast has a fantastic shot at verifying.  The danger is in my assumption that Philadelphia remains in the warm sector and is deprived of snowfall.  A single large storm could completely derail my entire forecast.


What is next?

Now that you all have read the most amazing winter forecast available on the interwebs, you need not have to go anywhere else.

Don’t believe that, I was lying to you.  Almost every forecast issued on the web has some scientific backing to it.  Throw 10 meteorologists in a room and ask them to make a forecast, and you will likely get 5 different forecasts for 10 different reasons.  I will not try to hide other forecast from my readers, in fact I will show you all of them and even link to them so you can see why they made that forecast in the final part of this exciting series. Expect it in the coming week!