The second week of March could be interesting around here. Every time the AO (Arctic Oscillation) has gone negative this year it has snowed in the Philadelphia area. When it went negative in January we got hit with sustained cold and snow. Then we warmed up. When it went negative in February, we got hit with a couple of days of cold and snow. Then we warmed up. So now here we are again in March and all of the sudden the AO looks like it wants to go negative a third time. Now it may not drop as deep into negative territory as it did in January and February which would lead to a weaker signal this time around, but negative, nonetheless. Remember, when the AO goes negative arctic air is on the move! This is also supported by the NAO (North Atlantic Oscillation) going negative during the same time. When the NAO goes negative, you get the trough in the east. The trough is where pressures drop which eventually leads to colder temperatures and unsettled weather.
The fact that it’s been really mild already and it’s going to be in the 60s again next week won’t matter. The snow we had earlier this month proved that. All it takes is for everything to line up just right or a system to come in at night (when temperatures are at their coldest), and you can get snow. It does become increasingly more difficult though as we get closer and closer to Spring. In conclusion, I just want to be clear that I’m not saying it will definitely snow again. I’m just showing you the pattern that may develop in the next two weeks which is very similar to the one that produced accumulating snow in January and February. So, we’ll see what happens.
