Late Morning Models...Most Snow As the Storm Departs?

The morning computer model runs from 12z are now in. Here is the breakdown.

12z NAM: Precipitation will impact Southern New Jersey about 60 hours from now. The “540 Line” is above Cape May County and along Cumberland and Atlantic Counties. So there would be rain or some mixing in Atlantic City and Cape May and snow above that line. At hour 66, there is nothing but light snow on this model for the southern half of the state. However, a secondary plume of moisture seems to develop around Baltimore and Washington and by hour 72 this would clip Southeastern New Jersey. The “540 Line” pushes well off the coast so this would result in a light accumulation of snow if this model were to be believed. The storm is all offshore by hour 78.

12z GFS: Precipitation arrives by hour 54. The “540 Line” quickly rises into Northwestern New Jersey and Eastern Pennsylvania. This means rain is likely, perhaps initially mixing with sleet, for much of Central and Southern New Jersey. There could be some initial cold air leftover at the surface allowing for some freezing rain. Whether this gets prolonged is the big question on this model run. By hour 60 the storm intensifies offshore. A notable shift eastward in the “540 Line” is noted here, but it does not shift east enough by hour 60 to give the state a change back to wet snow. By hour 66, it does shift east and the GFS from 12z gives New Jersey heavy precipitation with the heaviest in Central and Southern New Jersey. The line shifts well offshore as the storm pulls away. The model would give the entire portion of Central and Southern New Jersey a pretty decent snowfall as the system pulls away, although some sleet could occur as well. The model shows portions of the state having 0.75 to 1.00 of liquid to work with which under normal circumstances would be 9 to 12 inches of snow without sleet. My guess would be (if this model is correct) that some of the snow would initially melt into the big puddles, but that a flash freeze would occur.

It is worth noting how both models changeover whatever precipitation we have in our region to wet snow as the storm is in the final six hours. My current feeling is that the NAM model is too dry. I think an overall trend will develop where interior sections have a very brief period of snow or wintry mix. The warmer air would then change the sleet or wet snow to rain. Then we have to see whether the surface is warm enough for plain rain or if there is going to be a corridor of freezing rain. After the change to rain, the ending of the storm would appear to bring the best chance for accumulating wet snow and sleet to Central and Southern New Jersey. This could end up being a four to six hour period of accumulating snow and flash freezing conditions. However, I caution this scenario has not always played out and is not normal for a storm in New Jersey. If you are traveling to Northwestern New Jersey, it appears as though it would be snow to a wintry mix and then back to snow.

I would also note that the 06z NAM run was more in line with the GFS from both 06z and 12z, although the 06z NAM was colder.

Mid-Week Storm Late Night Model Analysis

The "540 Line" is the blue line on the images. For simple purposes just know that snow likes to occur when you are north of the line.

Late Tonight, the 00z NAM model suggests only Southeastern New Jersey getting some precipitation. The model has the “540 line” right around Cape May and Atlantic City which tends to indicate some sort of wintry mix or rain/snow mix would be possible. This model shows the coldest air and best chance of frozen precipitation as the precipitation ends.

Late Tonight, the 00z GFS model suggests a coastal storm. Despite the area being on the “colder side”, the air on the colder side is not cold enough for snowfall initially. The “540 line” lifts into Northwest New Jersey and Eastern Pennsylvania. However, as the storm intensifies and begins to move away, the model drags the “540 line” well into the ocean with heavy precipitation indicated over New Jersey. If one looks at this model closely, it would be interpreted as rain with some sleet and snow at the onset, followed by heavy rain with ice in Northwest New Jersey, ending as heavy snow and sleet.

Once again, we have two very different solutions with the same time stamp and also solutions totally different from the previous runs of the same models. It is not common to see accumulating snow in our region after warm air and heavy rain with the same storm. But it has happened before and in fact happened the other day in parts of South Jersey. If the GFS were to be believed, two to six inches of snow and sleet would occur on the backend of the storm in Central and Southern New Jersey along with the potential for a flash freeze.

1/23/2011 Extended Forecast: Winter Storm or No Storm?

There is no doubt tonight will be a very cold night with record-challenging low temperatures likely over a widespread area. Last night, the rural suburbs of Central New Jersey went down to 8 degrees below zero and in some cases 9 degrees below zero. These temperatures are unprecedented for New Jersey. Ideal conditions developed where you had clear skies, calm winds, an arctic air mass, and a decent snow cover. Tonight, we have a reinforcing shot of arctic air along with clear skies and expected decoupling winds. However, the wind speed will be critical. If the wind is not calm, you may have values around zero, but not as far below as early today. At this present time, I will go with a range of 10 below zero to 5 above zero for minimum temperatures. Your higher minimums will be in the urbanized areas. You will also find higher minimums in Southwestern New Jersey where there is less snow cover.

If there is just the slightest breeze, hazardous wind chills will be possible. The wind chill advisory criteria for Central and Southern New Jersey is when there are wind chill values of 10 degrees below zero. For Northern New Jersey, it is 15 degrees below zero. The wind chill warning criteria is 25 degrees below zero. I do not believe anyone will reach the warning criteria, but it may come close in Morristown or Somerville should these areas drop to around 10 degrees below zero early Monday Morning. I definitely think wind chill advisory levels could be reached again because even the slightest breeze with the temperatures we are forecasting can take us to the criteria threshold. Frostbite usually occurs within one hour when we see values such as the ones I am forecasting tonight and the advisory levels usually mean frostbite will occur within one-half hour. Right now the National Weather Service will not be issuing the product, but I can easily see us reaching this criteria. The criterion was met in several areas last night just by temperature and the product was not issued.

Regardless of whether you have an advisory or not, it is highly recommended that you bundle up before going outdoors in the morning. Make sure the kids are also wearing a jacket, hat, scarfs, and gloves as sometimes they can be waiting at a bus stop for more than one-half hour or they walk a long distance to school.

A 5 MPH wind & a temperature of 10 degrees combine for a wind chill of 1 degree above zero.

A 5 MPH wind & a temperature of 5 degrees combine for a wind chill of 5 degrees below zero.

A 5 MPH wind & a temperature of 0 degrees combine for a wind chill of 11 degrees below zero.

A 5 MPH wind & a temperature of -5 degrees combine for a wind chill of 16 degrees below zero.

A 5 MPH wind & a temperature of -10 degrees combine for a wind a wind chill of 22 degrees below zero.

Monday will be the first day in quite a few years where the majority of New Jersey will not rise out of the teens for high temperatures. The best chance of hitting 20 degrees will be in the cities and along the coastline. It should remain sunny for the entire daylight period. Some clouds will arrive on Monday Night.

Tuesday at this point looks to be mostly cloudy as some warm air advection streams into New Jersey. At this point, the models are now keeping much of the area relatively dry.

The big question for Wednesday is will there be a major winter storm or not. Every single possibility that could happen has been thrown out there. The models are in a great deal of disagreement. Yesterday the GFS model indicated an out to sea solution as the cold air will be entrenched and block it from striking us. The GFS lost this idea late last night and I thought we would be in the clear. But now the 18z NAM and 18z GFS has brought back the idea of the storm going out to sea. Just know that the models seem to develop a westward shift overtime prior to the event. If that was the case, perhaps it is not close enough for a mix…but close enough for at least some snow.

The modeling delaying this storm until Wednesday would lead one to think that the core of the arctic air has time to exit the region. Therefore I would think that the very cold air would not be entrenched for the storm and that it would also be weak enough to prevent strong blocking that would protect the Middle Atlantic. This is such a strong outbreak of Arctic air that I cannot rule out that it lingers into Tuesday. Right now, I see highs around freezing for Tuesday. While I am skeptical of the idea of an out to sea storm, I can see the credibility of this idea when looking at the extent of the current cold and reviewing previous storms of the past decades that turned out to sea when approaching a very cold air mass.

For the moment, I will push this idea to the side. However, I will not hit the delete button on it quite yet. If we see a coastal storm, it looks to be centered to strike New Jersey on Wednesday.

I noticed something very interesting today on the North American Model run from 12z which I think could be more credible than the newest run. This run showed the rain and snow line setting up along the Delaware River in South Jersey and along Interstate 195 in Central New Jersey. With our previous storm system, this is exactly where the rain and snow line stopped. Today when I was in Monmouth County, as soon as you travel north of Interstate 195, not even by a mile, all of a sudden you run into a fresh snow cover. My observer in Riverside also noted that she picked up more snow than in the rest of Burlington County. This also confirmed the radar imagery with the last storm showing that this is where line of difference set up shop. Also, similar to the previous snow, colder air would come in at the end of the storm changing any mix or rain back to wet snow. The only differences on this run from the previous storm are that the storm would last longer, contain more moisture, and be stronger.

The 12z GFS has the storm further offshore, giving New Jersey precipitation, and not much west of the Delaware River. This would give the coastal sections the most precipitation. This track would be colder with snow inland and rain along the coastal counties with mixing in-between. To repeat, the 18z GFS shows no storm at all.

If we should see a storm track where the area of low pressure rides over our region, as the ECMWF suggests…we would see rain and the dividing line between rain and snow would push into Northwestern New Jersey. The EURO has been the only model of consistence. It is worth watching the model to see if it also trends offshore. We will not know until 1:00 a.m.

However, SHOULD WE see the storm track JUST offshore, I am thinking that the dividing line will set up along the Delaware River and along Interstate195. North of this area there could be heavy snow and sleet, along with freezing rain. It should be noted that no storm is exactly alike. I am also thinking that for the first part of the storm, just as in the previous storm, there will be a battle zone between County Route 537 in Burlington and Ocean Counties and the Atlantic City Expressway. This is the zone where cold air damming could make all the difference between rain and freezing rain. For Atlantic City and Cape May, these areas look to see a brief mix or no mix at all with a coastal hugger. Again, a further offshore track could mean mainly snow or no precipitation at all.

This storm has the potential to be loaded with moisture if it does strike, particularly with a close track. In fact even though you see the newest American models showing an out to sea solution, the precipitation associated with the system is quite impressive. This raises several concerns IF this is in fact the case. If the cold air damming holds on the onset…..just in those first few hours you could have several inches of snow or quite a bit of ice accretion before the change to liquid rain in some areas. Where it remains all snow in New Jersey, if it does at all, you would be talking about a substantial snow accumulation. Where it remains ice, you could be talking about a serious accretion of ice. Finally, where it rains, due to the wet ground, we could have some flooding concerns. The prospect that New Jersey could be divided into three sections by precipitation types is certainly interesting. Then again we have this brush of a storm idea which would mean just an average amount of liquid we would have to play with or really none at all.

Wind could be a factor as well if this storm is a coastal hugger or if it tracks over us. The track is critical in determining the wind speed and wind direction. This has consequences as far as the chance of coastal flooding. If it coincides with heavy snow or heavy ice…there could be some power outages. If there is heavy rain, the ground could be very soft and it would not take much more than a 40 mph gust to take down some shallow rooted trees. Areas that see strong winds and heavy snow may be looking at near blizzard conditions. The idea with this rambling and throwing out all these possibilities is to get you thinking about what may happen with each of these different scenarios’ that have been thrown out at us.

Model flip-flopping makes this a very difficult forecast. We are still 72 hours away from this event. It is also interesting that the new NAM model is showing this storm at our latitude late Wednesday, which would result in a further delay. This storm looked to be hitting us on Tuesday yesterday and this would have put us in the 48 hour period where we would have much better confidence. Now with this starting later on Wednesday, we may have to wait until Tuesday Morning before getting a much better idea.

Other notes: I am also a part-time forecaster for the site http://phillyweather.net . I will also be filling in for the site founder this week as he is going to be out of town on business. So check that site out as well. Brian, a founder of the site http://cnyweather.blogspot.com is also a colleague on that site and will be filling in as well. If you headed up to Oswego at any point in the future, be sure to check out his forecast for that area.

for updates as new information streams in.

Extreme Cold This Morning in Central New Jersey, Amazing Rise

Across Central New Jersey this morning, the drop in temperature was quite impressive. Somerville, Somerset County dropped to 9 degrees below zero. Such a drop is extraordinary for New Jersey and is without a doubt record smashing. This was recorded at 6:53 this morning.

Conditions across the State of New Jersey became ideal for radiational cooling to occur overnight. The clouds thinned much faster than anticipated and skies became clear. The winds also became calm which was also lower than anticipated. But in Central New Jersey, where these below zero values were recorded, there was snow cover over a widespread area from the winter weather event that occurred late last week. Nobody forecasted such a drop in temperature last night across Central New Jersey.

What may even may more phenomenal then the low minimum is the rise in temperature in the span of one hour this morning in Somerville. The temperature climbed from 6 degrees below zero to fifteen degrees between 7:53 a.m. and 8:53 a.m. this morning. That is a 21 degree rise in temperature in one hour!

Morrisville also went down to eight degrees below zero this morning. The temperature climbed from one degree to seventeen degrees in the span of one hour. That is a climb of 16 degrees in one hour.

Tonight into Monday Morning was expected and still is expected to be the coldest night of the season for everyone in New Jersey. It is also expected to be a night of record-smashing low temperatures. These drops last night suggest that even lower temperatures could occur should the ideal conditions of calm winds, clear skies, and arctic air be in place overnight. I think the biggest obstacle to overcome tonight will be the wind. We need that wind to be calm, which is looking at this moment as a good possibility. We will have the clear skies and reinforcement of arctic air.

Later today I will have more on the mid-week storm. It is looking like the bulk of this storm may happen on Wednesday now.

Late Night Model Runs on Winter Storm Threat

The North American Model is still out of range on the 00z run, but it will be in range on Sunday. Based on the latest run of the model, it would appear that the storm system would be taking an inland track on this run which would result in warmer air moving into the region changing over the precipitation to freezing rain or even plain rain. If this is the case, we would be looking at the potential for significant flooding or significant icing depending on where you live in New Jersey because the system will be loaded with moisture. The “540 line” retreats to the north and west in advance of the precipitation arriving in the area and you need to be north of that line if you want snow.

The Global Forecast Model has shifted the track a bit further to the west tonight on the 00z run. The track on this run is still to our east, meaning we would be on the colder side of the storm. The “540 line” does retreat back to the north and west a bit, especially in Southern New Jersey. This means that this would be a mixture of snow, sleet, and freezing rain with a bit of plain rain along the coast.

A lot to watch on Sunday.

1/22/2011 Extended Forecast...Plus Latest on Storm Potential Tue./Wed.

I know everyone wants an update on the winter storm threat that looms, so let me talk about it first. Then I will get to the brutal cold. There continues to be a threat of a significant storm system on Tuesday into Wednesday. A trend has developed today, but there is no certainty that this trend will hold. Some of the more reliable modeling has taken the storm track and shifted it to our east. What I believe is happening is that the models are beginning to pick up on the fact that the colder air will be too strong of a force and this cold air will block the storm from cutting up directly at us. We just now have to be careful that the cold air and blocking pattern is not strong enough to avoid an event for our area all together. I still would like to see another two or three rounds of model data before I am confident that the wetter/icier vs. white solution will not take place. But it appears confidence is growing for a colder storm across Central and Southern New Jersey which would favor increased chances for frozen precipitation.

I want to clarify a rumor I have been hearing today about this storm. If you are on the colder side with a storm passing to your east…you will automatically have snow. This is FALSE. In the Summer time, occasionally you have a coastal storm that passes us by. However, WE DO NOT see snow. When one says that we see the colder side, it is implied that the air flow will be from a direction that typically draws in or maintains a cooler regime. If the storm tracks to our west, we would be on the warmer side because usually the air flow will be from a direction that typically brings in warmer air. To be more specific, an eastern storm track brings in northerly wind component of some sort and a western storm track brings in a southerly wind component of some sort. The air around an area of low pressure is counterclockwise in the United States.

The 12z GFS and 18z model shows very little in precipitation with the storm tracking well to our east as it is being blocked by a very cold, arctic air mass. Prior runs showed a significant snowstorm with some mixing involved along the coastal counties.
The 12z ECMWF or European model shows a good size snowfall for our region, but not the most dramatic of storms we have seen in the past year. It too gives an idea that there will be some sleet and freezing rain down at the immediate coastline and perhaps in the Southeastern NJ areas.

The 12z and 18z NAM continues to show a strong low pressure area developing in the Southeastern United States. This low then moves northeast on the model. However, the model only goes out to hour 84 and therefore I cannot get a good feel as to where the model brings that low center. The NAM I feel has done a fairly good job this winter and so tomorrow I will take this model and the output somewhat seriously.

The energy is just beginning to enter a region of North America where there is much better instrumentation and sampling of the atmosphere. This will be critical in determining where exactly this storm will track. Equally as important will be the clipper passing by tonight that will set the stage for the exact placement of an area of high pressure to our north. Until we verify where this exactly sets up, there will be lower confidence in the forecast. This will be the key in determining how much cold air is locked into place and where the blocking sets up.

At the present time, I will discount the one model indicating a complete miss. This storm has the potential to bring three to six inches of rain, 12 inches or more of snow, or serious ice accumulations. It just depends how all the cards fall into place. It is worth repeating that although I am dismissing it for the moment; we just now have to be careful that the cold air and blocking pattern is not strong enough to avoid an event for our area all together.

Moving on from the subject of a storm potential for a moment, I hope you stayed indoors as much as possible today. It was downright frigid outside. Much of the day was spent with temperatures in the teens. The sunshine hid behind several cloud layers this afternoon. Without the sunshine, it felt even chillier! The brisk wind today gave us single digit wind chills during the day which made it feel all the more brutal outside! The European Model last weekend was dead on with the idea of an arctic attack striking us this weekend.

A clipper system will pass to our north overnight into Sunday Morning. It will bring clouds to our region. Therefore, temperatures will not drop like a rock tonight. The wind will relax quite a bit tonight and pick up very briefly on Sunday as the clipper slides a cold front throughout area. Since the air mass is very cold, single digits to lower teens are still likely for low temperatures.

On Sunday, there will be morning clouds followed by afternoon clearing. The morning clouds and very cold start in this type of air mass point to another day with temperatures well below freezing. Highs in the middle twenties seem reasonable. There is a slight chance of a snow squall or a snow flurry with the passing front, although most of the high resolution models point to a dry passage. I think the better chances of this happening will be in the northwestern portions of New Jersey. Sometimes these snow showers do make it down to about Route 1 or Route 130.

On Sunday Night into Early Monday Morning is when I suspect we will see the coldest minimum temperatures. Skies will be clear, there is some snow cover around (especially into North-Central New Jersey), and we will have calm winds. The heart of an arctic attack will also be over us. These factors point to single digit lows being possible in the cities of New Brunswick and Camden with lower single digits elsewhere. Some of our coldest suburbs could definitely go below the zero degree mark for a time. This includes Somerville, Chatsworth, Lakehurst, and Millville. This cold is the kind that can cause serious water main breaks in the urbanized areas of New Jersey. Everyone will also be using their heaters and this is typically when we see some fires break out in homes. The fires that do break out will be difficult to contain as the extremely cold temperatures will cause ice to form around the scene very quickly when firefighters use water to douse the flames. A range of -5 to 5 seems reasonable. Being that I am thinking the wind will be calm, wind chills should not be a factor. However, if you get just a slight breeze it could be pushing wind chill advisory criteria.

The latest information is suggesting that Monday could actually be colder than Saturday and Sunday! I think temperatures will have an extremely difficult time recovering from the overnight low temperatures. The core of the arctic attack may not retreat until later in the day. I am going to forecast a high of 19 degrees for Monday. Yes, it may make it to 20 degrees. But the idea here is that outside of the urban heat islands….teens will most likely be the outcome.

One more note: there could be a lull Tuesday and Wednesday at some point. It is too early to nail down whether this will be the case.

Other notes: I am also a part-time forecaster for the site http://phillyweather.net . Saturday is my day of responsibility for this site, so a more regionalized forecast for the Delaware and Lehigh Valley can be found there today and every single day. I will also be filling in for the site founder next week as he is going to be out of town on business. So check that site out as well. Brian, a founder of the site http://cnyweather.blogspot.com is also a colleague on that site and will be filling in as well. If you headed up to Oswego at any point in the future, be sure to check out his forecast for that area.

I will remain committed to tracking this potential winter storm throughout the remainder of the weekend and next week.

Bitter Cold

The coldest temperatures in years could occur within the next three days.

Highlights:

Today we will see highs range from 20-22 degrees in the interior.

Sunday we will see highs range from 23-26 degrees in the interior.

Sunday Night into Monday Morning: The coldest start in years. Lows will range from 5 below to 5 above. Even the cities will drop into the single digits.

Monday: Highs will range from 17 to 19 degrees.

A degree or two higher along the coast near the ocean and a few degrees lower in Northwest New Jersey.

This cold will then set the stage for a storm system that will arrive on Tuesday into Wednesday. Many questions remain and I will have more on this system later this evening.