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Video showing the NAM model and NWS discussion on the storm for the Long Island area:

This video from the NAM goes from 7:00 this evening to 1 AM Wednesday.


Here is the forecaster discussion from the National Weather Service covering Long Island and Tri-State area:

Snow spreads across the rest of the forecast area where it hasn't already as thermal profiles support snow through at least noontime/early afternoon Monday for most of the forecast area. Lift/upward forcing becomes stronger roughly mid-morning into the the afternoon with an approaching low level jet and increasing 850-750mb frontogenesis, with models signaling a band of strong frontogenesis slowly pushing north through the forecast area during this time. This presents the potential of mesoscale snow banding for a good portion of the forecast area. Moderate to strong omega either within or not too far beneath the dendritic snow growth zone during this time could spell 2-4 inch per hour snowfall rates within this band(s). For coastal areas, winds 20-40 mph with gusts 40-60 mph will help create near-blizzard to blizzard conditions from roughly mid-morning into the afternoon, possibly even into the evening. Working against this however is that an elevated warm nose then likely pushes into much of Long Island and SE CT, possibly even into the city as well. This then introduces mixed precipitation for these locations, with even a complete changeover to rain across the Twin Forks and potentially even coastal SE CT with the help of boundary layer temperatures and the warming aloft. Do not have enough confidence of 3 hours of blizzard conditions to go with a blizzard warning - whether it be due to uncertainty of PCPN type or winds being consistently strong enough while it's snowing. There is still a potential that some areas get converted to a blizzard warning if confidence increases. The strongest frontogenesis is likely to the north of these areas in the evening, so dynamic cooling won't be much of a factor for much of the forecast area at this point. Thermal profiles probably don't change all that much late night Monday through Tuesday morning, so periods of snow inland/mixed precipitation LI/SE CT continue. Some models even suggest frontogenesis ramping up INVOF the Hudson Valley during the day Tuesday. Thermal profiles Tuesday afternoon cool off with precipitation chances dropping off somewhat, but still likely, or at least with snow becoming less steady. A mix changes back to snow for eastern sections of the forecast area during this time. Most of the snow accumulation will occur Monday afternoon and night, with light accumulations during Tuesday. Only change to headlines was to include eastern Suffolk County in the Winter Storm Warning. A good portion of the area probably sees at least 6 inches of snow before mixed precipitation pushes in. Forecast snow amounts might even be a little too low with snow amounts in the Twin Forks area. Followed fairly closely to WPC guidance for QPF which seemed reasonable and adjusted snow amounts upward a little where mesoscale banding can occur and/or temperatures are cold enough to support more than a 10:1 ratio.



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