Tuesday, February 1, 2011

Feb 1-2, 2011 Storm Updates

Below, storm updates will be posted on the major ice storm that is currently affecting the area.


8:25 AM: Overnight, widespread moderate freezing rain affected the area, with ice totals generally over 1/4 inch across most of the area, along with some sleet further inland. Long Island has already changed over to rain and New York City is currently changing over from south to north. Northeastern New Jersey will change over between the next 1-2 hours along with southwestern Connecticut as temperatures warm up above freezing.

The storm is moving faster than expected, and the worst of it has already moved out of the area - the heaviest precipitation was supposed to be this morning yet the main part of the storm is starting to end for the western parts of the area and will end further east over the next 1 to 4 hours. Behind the end of the storm, temperatures will warm above freezing, well into the 30s in the immediate NYC area, leading to some melting of the ice, and a few showers are possible through the afternoon. By the evening, temperatures will start to cool down into the 20s with a few rain or snow showers possible early.

9:35 PM: Over the last two hours, the area saw a widespread light freezing drizzle, leading to an additional coating of ice on surfaces. Temperatures are currently in the 20s across the area, but with 850 mb temperatures above freezing, representing a cold air damming set up, which can also be seen on the latest radar, as rain entering Pennsylvania from west to east is moving into colder temperatures and turning into freezing rain.

The storm is moving slightly faster than originally expected, and will start to affect the area from 11 PM to 3 AM from west to east. Widespread freezing rain will develop, though especially in the northern parts of the area, the storm could start out with some sleet. By the morning hours, a widespread moderate freezing rain will affect the area. The first place to change over will be Long Island, followed by NYC between 7-9 AM. Southern Connecticut and NE NJ will also change over gradually between 8 to 11 AM. In these areas, moderate to heavy rain will continue falling, ending by the early to mid afternoon hours. Freezing rain totals are expected to be between 0.1 to 0.3 inch in Long Island, 0.2 to 0.4 inch in New York City and coastal southern CT, and 0.3 to 0.5 inch in NE New Jersey.

For the interior parts of the area, however, this will be a different story. Temperatures are expected to remain below freezing through most of the event for interior SE NY, north central NJ and northwestern NJ. Some places may mix with rain towards the end of the event, however the main precipitation type will be freezing rain. Ice totals between 0.4 to 0.7 inch are expected
by the time that the storm ends in the early afternoon.

Another brief update may be posted later tonight, otherwise the next update will be posted tomorrow morning. A brief update on the weekend storm may be posted, with the latest expectation for more of a rain/snow mix storm for the area, potentially leaning more towards rain, especially due to the lack of cold air around, preventing this from becoming a plain snow event.

7:00 PM: The round of precipitation this morning ended up busting too far on the high side, as the changeover to sleet happened much earlier than anticipated. I went with 2 to 4 inches for New York City with my forecast last night, which was lower than what some models showed, however even that was too generous, as places from NYC and further east failed to see amounts over 1 to 1.5 inch. Precipitation then changed to light freezing rain, with ice totals between 0.1 and 0.2 inch so far. There is even more ice to come tonight, however.

We are currently seeing cloudy skies with scattered light freezing drizzle, which is leading to additional light ice accumulations. 850 mb temperatures are above freezing, however further down near the surface, temperatures are below freezing, in the 20s. As the snow is falling through the layer of warm air, it melts and falls as rain, and as it reaches the surface where there is a layer of cold air, it is unable to refreeze into sleet, and instead falls as rain which freezes on contact with the surface, or in other words freezing rain. This is the type of scenario we will be seeing tonight into tomorrow morning.

The storm is currently entering western Pennsylvania, and will continue to move east, reaching the area late tonight. Widespread freezing rain will fall across the area, changing over to rain in the immediate NYC area by 7-9 AM with a total of 0.25 to 0.5 inch expected north and west of NYC. More information on the forecast for tonight will be posted in an additional update between 8 and 9 PM.

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