NAM Model showing heavy snow Saturday evening

Although not impossible by any stretch, accumulating snow in non-elevated areas during the month of  October is nearly unheard of it in our forecast area. Very literally, the statistics are there to back it up. For instance, over all of the years which snowfall records have been recorded (a pretty long time), the maximum October snowfall at Newark, NJ is 0.3". That's less than an inch--the record snowfall at Newark, NJ for the month of October. The forecast models over the past several days have shown a wide variety of solution, from storms missing our area completely out to sea, to storms coming close to the coast, to (most recently) storms tracking off the coast and giving our area rain and snow. The issues lies in the fact that the transition to snow once it occurs, could be dramatic. The snow could be heavy for a few hours, leading to the potential for accumulations. However, this leaves us with plenty of questions. How can we best approach the forecast for this storm system? We'll take a look at it below.


Before looking at finer details, it's important to look at the reason why the storm is occurring to begin with. In this case, the storm is developing as a result of a highly anomalous disturbance in the atmosphere, which is diving southward from Canada. The disturbance will cross the international border in the North-Central United States, and then make a bee-line for the Tennessee Valley. Here, a very important interaction occurs. The storm is expected to phase and interact with another disturbance near the Southeast United States. As the two features interact, the will force the development of a surface low off the east coast. The interaction is integral, as it allows the storm to develop in a nearly perfect spot and with just enough strength. The forecast models have been trending towards bringing the storm closer to the coast, as they have a stronger and faster interaction between the two features.


Here's a touchy subject for sure. The forecast models have been incredibly inconsistent with the track of the system. In fact, just yesterday most of them had the system missing our area completely or just barely scraping us with light precipitation. However, over the last 24 hours an alarming and sudden west trend has occurred. Forecast models are now tracking the storm from just off the Carolina coastline, to east of the New Jersey coast, to eventually near the 40/70 Benchmark. Such a track would bring very heavy precipitation to our area--and very impressive atmospheric dynamics (we'll talk more about those next). However, it's hard to say if the west trend is finished, or if the storm may track farther west. This would keep the system mostly rain across our area. We'll have to watch the forecast models very carefully over the next few days.


The magic question. The answer is quite complicated, actually, and it really opens your eyes to the processes that occur meteorologically to get snowfall in our area. First, the storm system needs to take a favorable track. It can't be too far east or west (out to sea, or near the coast). The track is integral, also, because it dictates where the heaviest precipitation will fall. By nature, the heaviest precipitation often falls on the northwest part of a developing cyclone on the east coast. This is where we need to be if snow is going to fall in our area.

NAM model showing heavy precip & 30 F temperatures.

Why? Because the airmass is warm to begin with. Although it may feel like winter currently (it's pretty cold out there tonight), the atmosphere is still pretty warm. Too warm for snow. In order to get the snow in our area, we need the dynamics of the storm system to cool the atmosphere. In a process known as dynamic cooling, there are lower pressures aloft, and air cools as it expands. The strength of the storm and precipitation can cool the entire atmospheric column. Although temperatures at the surface may be in the mid 30's, not below freezing, the snow will still fall if the dynamics can cool things down. If precipitation is too light, it will fall as rain.


This depends highly on your location. As mentioned, the storm first needs to take a favorable track. Then, we also have to take into account the warm ground and surfaces. The snow definitely won't accumlate immediately. However, with time, it would begin to accumulate especially west of the city in the interior. The city itself will have more trouble accumulating snow on the warm streets and ground. The snowfall totals likely won't be anything we haven't seen before (1-3, 2-5 inches depending on intensity) --but the fact that it's occuring in October makes it remarkable.


Over the next day or so, we should begin to get a better idae on how the storm will transpire. However, from what we know now, the potential for rain switching to several hours of heavy snow does exist on Saturday afternoon. The storm could produce light to moderate accumulations of snow, especially inland and in higher elevations. We're depending on the itensity of the storm and precipitation to cool the atmosphere and allow the rain to change over to snow on Saturday. Finally, the entire forecast remains highly uncertain. Winter Storm Watches have been issued for Northwest New Jersey (interior) for the potential of 4 to 6 inches of snow.

Stay tuned here over the next few days. We'll be updating the forecast at least two times a day with all of the latest details. Thanks for reading through the lengthy article--and we hope it's helped you get a better understanding of why and how this system may occur.

NAM model showing low pressure along a front near the area on Thursday afternoon.

A strong gradient in the mid levels of the atmosphere will develop across the Northeast on Thursday , and the gradient will eventually extend down towards the surface in the form of a well defined frontal boundary, which will settle near the area beginning Thursday morning and afternoon. This frontal boundary will serve as a "highway" for low pressure and moderate to heavy precipitation to develop at the surface, as a strong disturbance moves over the boundary in the mid and upper levels of the atmosphere. Such a development will bring a threat of moderate to heavy precipitation to the forecast area, beginning on Thursday and continuing through Thursday evening. The precipitation looks to be somewhat spotty early, as mentioned above, so it won't be a deluge for your morning commute. However, by mid-morning the precipitation intensity should pick up, and it will continue on and off throughout the remainder of the day. Making the situation more complicated is the intrusion of significant cold air which is expected as the storm passes and the front sags south. This will bring colder temperatures into the system on Thursday evening, and the potential would exist for some frozen precipitation  in the higher elevations of the distant interior. The snow would be short lived and will stay away from the coast and the city as well as the immediate suburbs. The official forecast is below...


Today (Thursday): Mostly cloudy, with rain likely. High near 55. West winds around 5 miles per hour. A dreary and chilly day.


Tonight: Mostly cloudy, with showers likely. The showers could end as snow showers far north and west and in higher elevations. Otherwise, mostly cloudy. Low near 38. Cooler inland. West winds 5 miles per hour. 


WILD WEEKEND? This weekend looks to provide more dramatics, as the boundary settles offshore. Forecast models are indicative of the development of a low pressure system along this front, which could track north and then northeast up the East Coast. Such a track could (emphasis on could) bring the threat for frozen precipitation right back into the picture on Saturday, with the potential for snow, once again, away from the coast. However, the forecast models have been highly inconsistent, and it's going to take some time to iron out the exact track of the system. Some forecast models have the storm missing completely out to sea. Needless to say, we're watching it very closely. Stay with us for more details as the week continues. 

Article written by JH. Published October 27th, 2011 at 2:20am. Looking for a forecast? See New York Metro Weather's Long Range Forecast for the end of the week into the weekend, or view our Technical Forecast Discussion for the more serious weather enthusiasts. Also, check out our new Forecast Overview tab. For up to the minute details on forecasts, watches, warnings, and alerts, follow us on Twitter and Facebook.