Details on the Pi Day Nor'easter

                Winter Storm Warnings for most of the state have been issued with Blizzard Watches into Northeast New Jersey and High Wind Watches along the coast.  Everything’s coming together for our first and probably last major winter storm threat of the season where a lot of places could actually double their current snowfall totals for the whole season.  For example, I’ve measured 11.5” for the winter at my station in Cinnaminson, and I would not be surprised at all if we approach and/or best that by Tuesday evening.

                Models have been consistently showing this system since the latter half of last week, and it looks like all the ingredients are coming together for it to come to fruition.  We’ll likely see the full platter of weather that comes along with a winter nor’easter in the Northeast: high winds, heavy snow, low visibility, coastal flooding, and beach erosion.

                At this time, the first flakes begin to fly from southwest to northeast between 9pm and midnight on Monday night and quickly pick up in intensity.  We’ll see the heaviest of the snowfall between midnight and 10am on Tuesday morning.  The precipitation should dwindle in intensity and taper off during the afternoon hours. 

                Below is an image of this afternoon’s Hi-Res NAM model run showing a depiction of conditions at 8am on Tuesday morning.

Image courtesy of tropicaltidbits.com

                Though it is more likely for the coast and areas within maybe 20-30 miles of the coast, we could see the rain/snow mixing line approach the I-95 corridor from Wilmington to Trenton.  In areas that change over to sleet/rain, even briefly, snow totals would only likely hit the lower end of forecasted ranges along with eating away at snow that has already fallen.  As of now, it looks like it should stay away from the Philadelphia metro area, but it’s a possibility Tuesday morning if the storm's center tracks too far west and closer to the coast.

                As of now, the heaviest banding of snow is still questionable in exact location but likely occurs somewhere between eastern Pennsylvania and just east of the I-95 corridor.  During the AM hours overnight and into Tuesday morning, we could be looking at snow rates upward of 1-3” per hour which would cause visibilities to drop to a ¼” – ½” mile.  A blizzard is officially defined as a time period of 3 hours or more in which 35mph+ winds cause blowing snow with visibility of ¼” or less, and we could see that in some parts of the state during the storm.

                Speaking of winds, we’ll be looking at upward of 40mph wind gusts inland toward the Philadelphia metro area and gusts to 60mph+ along the coast.  That, as stated earlier, would lead to blowing snow and reduced visibility.  Also, this will be a heavier, wet snow that’ll tend to stick to wires and tree branches, so high winds could lead to the possibility of downed branches and power outages.  Again, this threat increases as you get closer to the shore. 

                Finally, for the coastal towns, we’ll be looking at moderate flooding with constant, high onshore winds on Tuesday morning combined with a high tide.  This wind and wave action will also lead to beach erosion as is a trademark of all major nor’easters.  High winds and coastal flooding/erosion are the two effects of this system with the highest confidence.

                Below is my second call snow map.  I’ve upped totals across the board with a jackpot area in North Jersey where heavy banding and no threat of mixing will have the best chance of occurring.  Then, the I-95 corridor of South/Central Jersey is the secondary jackpot area where we could see some high totals under heavy banding but any mixing of sleet and rain could do a number on snow totals if the rain/snow line makes it that far inland.  Then, totals decrease as you approach the shore due to the higher chances of mixing.

My Second Call Snow Map