Saturday, January 31, 2015

Updated Forecast for Sunday Night into Monday



Thanks for being patient guys I had to work a little longer than expected but above are my updated thoughts on the upcoming storm system. As we have been discussing the models have been trending north and that is reflected in this map. However, I do think certain models like the UKMET and GFS are a little too far north so I slightly adjusted them south. 

A few things to note:

  • Snow looks to break out in most areas late Sunday night
  • Snow changes to rain in the green zone and freezing rain in the pink zone
    • I expect the low level cold air to put up a fight which will cause the rain to freeze
  • In the red zone, snow accumulates early Monday morning but then sleet should mix in by day break . 
    • This will cut down accumulations in that region
    • There will be a paper thin gradient between 4 or 5 inches and 10 inches in this area depending on the intensity of the precipitation
    • The closer you are to I-80 the better for more accumulations
    • In times of heavy precipitation you can see a changeover to snow in the northern part of this zone which is why totals go up to 10  inches.
  • The bulls eye is southern New England with this storm
    • Some sleet may mix in to the south especially over NJ at times but overall I think its a significant snowfall
  • Storm should be over by the early afternoon Monday 


As always I will have a video update tonight around 6.

4 comments:

  1. Is Totowa nj in the 5 to 10 or more like 8-14 it's looks like you have borderline from what I can see

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  2. Willy, was looking at the 12Z runs of CMC-Global, GFS, NAM and UKMET on meteocentre site (bless those Canadians). Looked to me like GFS had the lowest snow total (about 6 inches) and highest rain line (around the NJ-NY border). CMC looked like the highest overall precip w/ 12 in snow plus rain, NAM had rain line down around New Brunswick w/ 10 in., UKMET runs I saw don't have rain/snow break-out, but UKMET temps go above freezing Tuesday pre-dawn in the "I280 corridor" where I live. UKMET chart implied 14 inches if all snow, but given temp forecast, say 8" snow. So, your 5-10 range seems quite reasonable right now. If I was reading it right, 12z GFS looks again like it's on the lower-snow / higher temp side, slightly contrarian. We will see if it can get 2 in a row. Also, today's NAO / PNA still + / -, trending towards a flip, but doesn't look like it comes by Monday. So, may still be some anti-trough bias, allowing warmer air further north? Both NAO and PNA looked above / below NOAA ensemble projection levels. But anything can happen, of course, this is real-world weather after all. Jim G

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    Replies
    1. Sounds like you read the outputs quite well. I think there are a few things to consider here some of which you touched on. There is a -NAO so this storm can only cut so far north due to the high pressure it is holding in place. When we are talking about a 20 mile gradient (northern NJ) it is extremely hard to pinpoint, but overall I think the GFS is too far north and it is allowing the warmer air too far north. A transitiioning NAO is a great things and many big storms have come from those transitioning peroids.

      Also, the snow cover in NNJ should help enhance the baroclinic zone for the storm to travel along. It is that baroclinic zone that will cause the tight gradient between warm and cold air which will cause intense precipitation. This intense precip will help cool the column and snow can hold in northern counties. What I think we are left with is an ice storm central NJ up to I-78 and a snow and sleet event I-78 north. The 5-10 I think is a good range to account for the sleet cutting some some accumulations.

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