Here's What You Need to Know About This Weekend's East Coast Snowstorm
A snow and ice storm will disrupt travel in the Mid-Atlantic and Northeast tonight and tomorrow, but it's nothing abnormal for this time of the year. However, "nothing abnormal" doesn't mean crap when you're sliding sideways into a ditch on I-95. Here's what you need to know to stay ahead of this weekend's weather.
The Setup
See yesterday's post for a detailed explainer on how this low pressure system came into existence—it's riveting, I promise. A coastal storm (nor'easter) is developing off just east of the Carolinas this afternoon, and it will steadily make its way north-northeast, paralleling the coast as it heads towards Atlantic Canada.
A solid shield of precipitation associated with the low is engulfing much of the Mid-Atlantic at this hour, with a steady, frigid rain falling at The Vane's nerdquarters in North Carolina. The vast majority of the precipitation is falling in the form of rain, but you can see the precipitation change over to snow and ice as it reaches the mountains in Virginia. As the shield pushes north into the colder air, we'll see more of this changeover to ice and snow.
Snow
The latest prediction from the various National Weather Service offices shows that snowfall accumulations won't be record-breaking or even memorable for this time of the year. A widespread coating of snowfall is likely from the Appalachians northeast through Maine, with the highest totals occurring in coastal areas of New England from Massachusetts through Maine and up into Canada.
When it comes to tricky storms like this, there's always a chance that some areas could see much more or much less than what's currently forecast. It only takes the rain/snow line nudging a few miles west to cut snow totals to nothing, and it only takes one persistent band of heavy snow to double an area's snowfall totals. This scenario is played out in National Weather Service forecasts. Look at the forecast for eastern Pennsylvania, for instance, which is under the jurisdiction of NWS Mount Holly, New Jersey. The office's current thinking is that this part of the state will see four to six inches of snow. The "worst case scenario" on their website is that this area sees up to nine inches of snow, and the "best case scenario" is that the precipitation stays rain most of the time, cutting totals down to a dusting at most.
A single-digit snowfall at the end of January is nothing when compared to history, but it can still be dangerous if you have to venture out on untreated roadways. Use common sense, and give yourself plenty of space between you and the other people (who never have any common sense).
Ice
One of the biggest problems with this storm might not be the snow, but rather the ice. We could wind up seeing an extended period of freezing rain in between the rain and the snow, which could create some very serious issues for major cities from Washington D.C. to Hartford, Connecticut. The National Weather Service currently expect about one-tenth to one-quarter of an inch of ice accretion in spots shaded in pink.
Keep in mind that some of these areas are still expecting a few inches of snow after the freezing rain, so the added weight of ice accretion underneath an accumulation of wet snow could cause tree and power line damage. Surfaces like roads and sidewalks will have a glaze of ice hiding underneath the snow, so surfaces that just look snowy won't look slippery until it's too late.
Rain
Those of us who are caught in the warm sector of this storm will enjoy a dreary, steady rain over the next 12 to 24 hours. The rain is coming to an end in the south, and it's far from ending in places like North Carolina and southern Virginia.
The latest forecast from the Weather Prediction Center (formerly the Hydrometeorological Prediction Center, or HPC) shows a couple of inches of rain under the heaviest and most persistent showers and thunderstorms deep in the southeast. The above precipitation forecast is valid for the next five days, so not all of the rain will come with this storm, but the vast majority of it will fall through the day tomorrow.
It's also worth mentioning that there's a marginal risk of severe thunderstorms in Florida and extreme coastal sections of the Carolinas, as atmospheric conditions are slightly favorable for the development of a few weak spin-up tornadoes and some damaging wind gusts in any of the stronger thunderstorms that swing through.
West Coast
I've gotten a few comments and messages over the past couple of days upset that I haven't talked about weather on the West Coast lately. There's a good reason for that.
There's not really any weather to talk about. The satellite image shows a huge batch of clouds over the Pacific Ocean and the northwest coast associated with a storm moving into British Columbia, but other than that, the only thing over land is Tule Fog in California's Central Valley.
If we look at the WPC's predicted rainfall over the next five days, you'll see that almost everything is confined to northwestern Washington and parts of Idaho and Montana, with negligible rainfall elsewhere. The forecast shows up to half an inch of rain possible southeast of Fresno, California, but that's a literal drop in the bucket compared to what the area needs to help alleviate the catastrophic drought.
[Images: NOAA, Intellicast, NWS x2, author, NASA, author]
