Discussion...
Here is our updated ice map for this storm. We decided to downgrade our 0.25-0.50 zone from our forecast from last night to a dashed zone for the possibility of having a few reports of Ice Accretion exceeding 0.25", but we are not expecting widespread amounts exceeding .25” at this time.
The other area of growing concern is across the North Country region of Upstate New York, specifically the Saint Lawrence River Valley and northern Adirondacks. The GFS is advertising an abundance of QPF in this corridor, which if right, could mean widespread significant icing of >.25”, however we suspect the GFS is a tad overdone in bringing this much QPF to the area, and we therefore are accepting a more NAM-like QPF field here. If by chance the GFS is correct, we think some of the QPF would likely be spent on a snow/sleet mixture to start as well as occasionally mix in, thereby reducing the icing potential. Having said this, we have highlighted this region for the possibility of localized areas receiving upwards of .25” of ice, although we are not anticipating widespread amounts exceeding .25” at this time.
Another area to keep an eye on is the Catskills region of Central New York, where HPC has actually pegged a 40% probability for 0.25” or greater. The amount of QPF is a question mark for this area however, so we decided to leave them out of a localized 0.25-0.5” zone.
All in all, confidence remains fairly high that many folks across the interior Northeast will experience an advisory-level event (.10-.25”Ice Accretion) with regard to icing.
Switching gears to the snow/sleet accumulation potential, the 2 most favorable areas to experience any kind of accumulation will be across the Adirondack region of Upstate New York as well as across Upstate Maine. In both these areas, a snow/sleet mixture is likely to start off, and could accumulate up to 1-3” before event transitions to more of an Ice threat with sleet and freezing rain becoming the dominant precipitation types, and eventually plain rain showers in most areas.
..GLUNT/EGAN.. 12/25/09
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