A Messy Weekend Ahead
by Cody Matz
March 07, 2013 7:58 PM
As this storm continues to trend further north, for those naysayers, it looks very unlikely that we will get through this weekend dry. In fact, many areas may see over a half inch of rain with some snow on top of that. But this is going to be one of those storms where every corner of our area will see something different. In many cases, one town will likely see drastically different precipitation than the next town just down the road. This is because temperatures will be hovering within a few degrees of freezing in most cases which means that a degree here or there could make a huge difference in not only what type of precipitation you get, but how much you get. For the moment though, it looks like the rain and freezing rain will over shadow the snow with not everyone likely to get the snowfall. All the details are below.
One of the first major hazards we are likely to face will be the possibility of freezing rain. For those that don’t remember, or have never known, freezing rain is rain that freezes when it hits the ground because temperatures at the surface are below freezing. This allows ice to quickly accumulate which can lead to dangerous travel and even power outages if the ice becomes thick enough. This could become a reality for some of us Friday night. From the Weather Prediction Center… these are the probabilities of receiving at least .01” of freezing rain and at least a .25” of freezing rain. A quarter inch or more would be considered significant accumulation where trees and power lines may start falling.
Looks like much of the area, with the exception of parts of the south, has at least a slight chance of experiencing some light icing. But the probability in the northeast is much higher thanks in part to expected northerly winds and the cold dome that significant snow pack can have on the lower levels of the atmosphere. These areas have at least a 50% chance of a quarter inch or more of icing.
So here is what we are expecting in terms of icing potential… the best chances will stay in the northeast.
The most abundant precipitation type will be rain… by far. This is a very April or May like storm bringing plenty of relatively warm air and lots of moisture along with it. Our futurecast shows widespread rain across much of the area, but remember, some in the north and west will likely fall as freezing rain.
These amounts are likely still low considering our futurecast only goes out to 7pm Saturday. More precipitation is expected Saturday night, especially in the east. Here is what storm total liquid amounts could be according to the Weather Prediction Center.
Like I said, pretty impressive numbers with up to an inch possible for areas along and south of I-90.
Even though rain and freezing rain will likely be the main impacts with this storm, some areas of snow are still likely with a few inches possible in some areas. But this storm will be quite a bit different from others. Temperatures will be very close to freezing in many layers of the atmosphere, which can lead to spontaneous change over to different types of precipitation. The longer that type of precipitation falls, the more you will get. Take the storm that went through DC this week for example. Temperatures were very close to freezing in a wide array of areas. The city of DC only ended up with an inch or 2 of snow because temperatures just couldn’t cool enough. But either side of DC some 20 miles to the west and 20 miles to the east got more than 8 inches of snow. This creates a scenario that is next to impossible to forecast for with any good accuracy so you are just gonna have to take what happens in stride and be prepared for whatever comes your way. So here is the snowfall potential. Below are 2 different forecasting models that show snowfall potential through the weekend.
Notice that these two are fairly similar, but have different placement. It looks like there will be a couple different bands of snow with breaks in between…. These types of scenarios are actually pretty common. The areas that these bands form have extra convergence, which leads to higher precipitation rates, which leads to additional cooling, which accelerates the change over from rain to snow. These bands of precipitation are called deformation zones.
Here are some maps for potential snowfall this weekend showing the probability of receiving at least 2, 4, and 8 inches of snow across the country produced by the Weather Prediction Center.
This shows good chances for at least 2 inches of snow across much of the area, but are drastically reduced when you go above 4 and 8. But the interesting aspect is that there is still a chance for both in spots which means the WPC is having just as tough of a time figuring out the expected change over to snow as we are.