By Kate Bilo
PHILADELPHIA (CBS) — After all the waiting, it has begun – our powerful nor’easter is now producing snow across the Delaware Valley and it has only just begun. Heavy snow will continue to fall through the overnight hours and into the early morning, piling up well over 6 inches in many areas, with even higher amounts in our far north and west suburbs where the snow could pile up over a foot.
All along we’ve been stressing the importance of the mixing. This will determine where snow totals will be limited versus continually climbing through the day. It looks like snow will continue to fall from the city on north and west through at least noon because warm air makes enough of an inroads to start the mixover. However, since last night the models have been consistent in bringing in a lull during the afternoon and early evening hours, where precipitation may lighten a bit. But don’t be fooled into thinking that’s the end of it!
Another portion of the storm that has been modeled today is the threat of a 1-2 punch with a band forming at the back edge of the storm as it strengthens off the New England coast. This could send a band of convective snow back into our area Thursday night and into the wee hours Friday morning. These bands are notoriously difficult to forecast because they set up where they want to, and often we see back-edge snows wrapping up quickly and missing to the north. However, there have been times where convective snow bands form, especially as a storm bombs out, and dump heavy snow over the region.
When I say convective, I’m talking about the same process that happens during a thunderstorm. Imagine a strong thunderstorm rolling through, where the rain just POURS for an hour or two? Now imagine that kind of rain in the form of snow, at a 10:1 ratio, and you can see how these bands can be responsible for serious snow dumps. We could even hear thunder during the storm, both on the front and back ends.
This is definitely an aspect of the storm we have to keep an eye on, because it may adjust snow totals higher by the time the storm winds down. But again, it all depends where the banding sets up.
We want to urge you to find a safe place to ride out the storm and don’t try to travel through it unless you have to. From the safety of a warm place, this will be a remarkable storm to watch. In addition to the chance for thundersnow, this storm will produce snowfall rates that could exceed 2″ per hour at times. It will produce very strong winds, to the tune of 35 mph. It will be a very long duration storm, lasting a staggering 28+ hours (including that brief lull). Definitely an example of Mother Nature at her most fascinating.
Be safe and as always, follow me on Twitter for up-to-the-minute updates. And tweet me your snow totals and pictures (use hashtag #CBS3Snow) and we’ll get them on the air!