Jan 31, 2011: Major Snow, Sleet And Ice Storm

Today brought generally partly cloudy skies to the area with chilly temperatures observed, however precipitation has already started moving into the Mid Atlantic and will move into the area later tonight from what will be a storm full of extremes, ranging from blizzard conditions in Chicago and nearly 20 inches of snow to a major ice storm from Pennsylvania into parts of the area.

Tomorrow’s Forecast: Moderate Snow/Sleet

Tomorrow will bring the first part of the storm. Precipitation will move in from the west late tonight, with widespread light to moderate snow affecting the area by the early morning. The heaviest precipitation from this wave, however, will stay to the north of the area, and with 850 mb temperatures rising above freezing, the snow will change over to sleet from south to north, first in the eastern parts of the area in the mid morning, the immediate NYC area in the late morning, and the northern and northwestern parts of the area in the early afternoon. Sleet will fall through the mid afternoon hours, when precipitation should start to move out of the area.

By the time that precipitation from this round of the storm ends, at least 2 to 4 inches of snow and sleet are expected for New York City and further south/east, 3 to 5 inches in the immediate NYC area, and 4 to 7 inches for the northern parts of the area, including parts of interior southern Connecticut and Orange County, NY. An update on this round of the storm may be posted tomorrow in the early afternoon.

Tuesday Night – Wednesday Night: Major Ice Storm

As previously mentioned, the 850 mb temperatures will rise above the zero degree mark for most of the area by tomorrow afternoon. Instead of surface temperatures warming up too, however, we will see a cold air damming scenario, where the cold air will remain trapped in the surface, so while 850 mb temperatures will be above freezing, surface temperatures will remain in the 20s. This is a set up for a major ice storm.

During the early to mid overnight hours on Tuesday night, generally dry conditions are expected, though a few light sleet or freezing rain showers are possible at times. Between 1 and 4 AM, precipitation will move in from west to east. While the precipitation type may start out as sleet in some places and potentially snow in the northernmost parts of the area, by the early morning hours, a widespread moderate freezing rain is expected for the area, leading to a dangerous morning rush hour.

As surface temperatures will warm up, places south and east of NYC will change over to rain by the morning, with NYC and its immediate north/west suburbs changing over to rain by 10 AM, which will be heavy at times. Places further inland, however, will have a more prolonged period of ice, and may fail to change over to rain at all. The precipitation will continue to fall moderately to heavily through the mid-late afternoon hours, when the main storm should end, with the potential of some light snow in the evening to the early overnight hours. With temperatures quickly dropping into the 10s and 20s, black ice is expected for the immediate NYC area and further south/east.

When this round of the storm ends, at least 0.2 to 0.5 inch of freezing rain is possible in the immediate NYC area, with the potential of over 0.5 inch of freezing rain further inland. This will be a very dangerous storm, and has the potential of bringing significant ice accumulations. Stay tuned for more information on this storm tomorrow.

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