Feb 7, 2013 Morning Update

Urgent Morning Update – Blizzard Increasing In Probability


Last night’s update was complicated by the 0z model guidance, which aside from the 0z ECM noticeably shifted southeast with the coastal low; as of last night, there was enough confidence to mention that there was still a possibility that phasing could take earlier with major snowfall extending into NYC, but not enough confidence to fully forecast this scenario. As of this morning, the model guidance continues to correct towards this solution, and at this time there is enough confidence to raise snow accumulations across the area.

As this is a morning update, this will remain brief, with more information to be posted this afternoon. The main factors that could result in lower totals than expected are more mixing with rain/sleet before the changeover to snow, or a slightly further east coastal low which would keep the heaviest snows further east initially. These areas of uncertainty will be addressed in more details later today. Below is the revised forecast for the area, which will be expanded with more information later today:

 


Light snow is expected to develop across the area on Friday morning, steadily intensifying up to the early afternoon hours. As temperatures aloft and near the surface warm up, a changeover to rain and/or sleet is likely in NYC, Long Island, and possibly NE NJ and coastal Connecticut for the afternoon and evening hours, while interior areas continue to see moderate snow. Accumulations will remain minor through the evening hours, generally up to 3 inches of snow inland and 1-2 inches closer to NYC.

By the evening hours, the coastal low pressure will approach the area, when the most significant impacts from the storm will begin. As temperatures begin to cool down, the rain/snow line will gradually shift southeast through NYC and Long Island in the late evening to early overnight hours, generally after 7-9 PM, with the entire area seeing snow by the early-mid overnight hours. The main question at this time is exactly how far west the deformation band ends up; Long Island and southern CT are likely to be covered by the heavier snow, which combined with strong winds gusting over 40 mph, will result in the potential for blizzard conditions. Thundersnow cannot be ruled out under the heavier snow bands as well. More moderate snow is likely west of NYC, with the snow gradually weakening later in the overnight hours before ending on Saturday morning. For more localized forecasts, please refer to the latest 5-day forecast.

There is still some uncertainty regarding exact accumulations, depending on the focus of the heaviest snow bands and the location of the low pressure, with the latest forecast totals revised to 6-14 inches towards western NJ, 8-18 inches in the immediate NYC area, and 14-24 inches of snow in CT and most of Long Island. These amounts are still subject to change, with more information to be posted later today.

Stay tuned for a more detailed update during the afternoon; tonight’s forecast discussion containing a final storm forecast will be posted earlier than usual, in the late afternoon or evening.

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