Thursday, January 21, 2016

Thursday Morning Update: Final Forecast Map Out Tonight, Some Thoughts This Morning

Good morning. We are now within 36 hours of our storm and models for the most part are starting to lock everything in. Areas from DC to Philly are really looking good right now in terms of significant snowfall potential. Also, I am getting increasingly concerned with coastal areas and beach erosion and surge due to the very strong winds this storm will bring with it. So before we go any further here is the latest:

  • Major winter storm on track to effect the area Friday night through Saturday
    • Storm arrives  late Friday night and ends late Saturday/Sunday morning
  • For areas in the epicenter of this storm a foot or more of snow is likely
  • For coastal areas winds can gust up to 50 mph, 40 mph inland during the day Saturday
    • Beach erosion will be a big concern since we are nearing a full moon
  • There is still a very big question mark about how north this storm gets
    • I will talk about this below
  • Due to the sharp northern cutoff in precipitation that ALL models are projecting 30 miles will mark the difference between significant snow and a few inches. 
    • Where this northern edge sets up will all come down to the placement of the upper level low pressure center and how close it stays to the coast

Ok so lets discuss what is going on very clearly. First here was my initial snow map..

This will be updated to a final map in my evening update. I can tell you right now as I mentioned last night that I will be cutting down the light blue (5-8") zone. I will also be tweaking the areas in southern CT and NNJ to reflect where I target this sharp northern cutoff to be. At this time it is likely to boarder extreme NW NJ through south central CT (near I-84 corridor). THIS WILL BE THE MOST CONTROVERSIAL PART OF MY FORECAST.This zone literally is the hot debated topic right now. Some will be happy some will be upset but I will do my best to make it accurate based on today's data and how it relates to my final thoughts on how this storm evolves.

I also will increase the resolution of this map meaning there will be narrower bands on the map to really hone in on the hardest hit areas. This will be especially important for all areas north of I-78 that are right on the brink right now between a lot of snow and a few inches. 

So lets go through some model updates.

Looking above you have GFS top left, Canadian top right and NAM model on the bottom. I circled on each model the factor that is going to make or break the northern zones- where does a deformation band of snow end up setting up. A deformation band of snow is a very intense area of lift in the atmosphere due to air getting stretched apart, it can cause snowfall rates over 2 inches and hour and will make or break this forecast. Notice on every model the band is in a slightly different spot. For example on the GFS model is is south of I-78, the Canadian model just over I-78 extending a little north and the NAM (most aggressive as always) has the band getting into the southern CT. THIS IS THE FORECAST KEY. The positioning of the upper level low and High pressure to the north will determine the position of this band. Anyone who is just off its northern edge will see a rapid decrease in snow amounts due to sinking air (what rise must fall).The models right now are trying to determine where this sets up. Believe it or not they will CONTINUE  to jump around a little where in one run Sussex county NJ can have a foot where in another they have 2 inches. This is because this is a micro aspect of the atmosphere and it very hard to predict outside of 24 hours. 

Hey Will how about the European model? Yes my friends the European is south with its northern edge of heavy snow banding. If fact, it cuts off the heavy snow just south of Newark NJ! Can this happen? Absolutely, but I want to make it clear I do not think that will verify. Its ensemble prediction system has many members still well north of the main model. This to me says it would be too early to make that call. I am sure if I am wrong I will take heat from many people but my honest assessment is that this will make it to NNJ/SE CT. I am basing that on history and how similar storms have behaved along with ensemble guidance. 

Regardless of what happens today in model land. My map tonight will reflect my most accurate attempt to give you guys the best final forecast 24 hours before this event starts. 

Stay tuned. I will have the final forecast up around 630pm. 

1 comment:

  1. AM update: Willy, what about the 0Z Euro and the 6Z GFS? If I'm reading right, both went down from yesterday, both now around 6 to 8. Also the 0Z GEFS appears to be offering more under-10 options, albeit some with freezing rain. That Canadian high once again appears to bounce along with the storm front, making it walk the gangplank out into deep water, staying SE of the 40-70. Right now, from what little I can tell, your 12+ scenario for Morris & Essex seems to side mainly with NAM and CMC. NWS seems to be splitting the difference right now, 9 to 12. Well, we shall see -- who knows, maybe the NAM and CMC will have their day. What is it that they call the final quarter-turn in a horse race? Jim G