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Weak Low Pressure to Blanket Northeast in Moderate Snowfall. (UPDATE) 2/17

Updated: Feb 25, 2019


The Northeast is expecting a moderate snowfall that will be very impactful for the morning commute during the morning hours of Monday. Snow will begin to overspread the area late Sunday night and should be at its peak early Monday morning.

Synopsis:

Snow will begin light in nature at first before slowly picking up in intensity as the hours go on. Snow will be moderate and could be particularly heavy at times especially for southern New England. The jackpot zone looks to be in the northern half of Rhode Island and south eastern Massachusetts.


Considering the pattern we are currently in it is surprising that we are talking about snow at all. There is currently a raging southeast ridge pumping warmer air into the region. a -PNA helping storms stay flat and not strengthen and a +NAO which is currently providing no blocking to slow the storm down and funnel in cold air. However these are the exact types of patterns to expect light snowfalls aided by a thermal gradient. These types of systems do not last very long and are not the big snowstorm that many are hoping for this winter but it is snow nonetheless. The one thing we do have working for us is a rather strong and setup high pressure to the north that is helping to suppress the southeast ridge.



The HRRR is showing moderately high lifting values in the DGZ layer, promoting decent but not great snow growth. For this reason I am heavily leaning to the lower end of the forecast. I was hesitant to even include a 5-8" value, however, I feel as though there is enough working for this potent storm to warrant the upgrade.


A great piece of guidance that has preformed very well in the past is the HREF ensemble models. They are relatively aggressive with the snow and cold, even forecasting 2-4" in New York city and as much as 8" in some spots. While I currently feel that that model is too aggressive it has preformed well in the past and needs to be monitored as we get closer to the start time of the storm.



Forecast:

Here is my ongoing and final forecast for the storm overnight tonight through Monday.


I am going with the middle of the road solution here. I do not want to be too aggressive because the pattern is not perfect plus the fact the system does not have a ton of moisture to work with as well as marginal lifting values. However I am not siding with the lower guidance either as I believe it is overestimating the dry air as well as the fact that temperatures are pretty low creating decent snowfall ratios. I am expecting about 1" in NYC, after a quick C-1" Precipitation will go over to sleet and rain limiting accumulations. I have the 3-5" line just north of Scranton headed north of Bridgeport. I expect most of southern New York as well as the good majority of Connecticut and Massachusetts to experience 3-5" of snow, including Boston. I expect the jackpot zone to be from northeastern Connecticut northern Rhode Island through Plymouth Massachusetts, those areas will experience 5-8" with heavier snow at times. Snow should begin to taper off for most around 8am Monday morning from southwest to northeast.

#Winter #snow