Dec 17, 2013 Storm Updates

A few updates will be posted on the snow and rain event affecting the area today. The next full forecast update will be posted on Thursday.

Blog Updates: (Regional radar from the Pennsylvania State University e-Wall)


2:45 PM: Snow Continues, Exceeds Forecast for some

radarAs of 2 PM, the coastal low is just off the central NJ coast. Minimum pressure is near 1013 mb, and the low is steadily tracking to the northeast. The low is currently deepening at approximately a rate of 1mb/hour, and is expected to undergo more rapid intensification tonight as it tracks south of Maine and into Nova Scotia.

For the short range, additional light to moderate snow will continue through at least 3:30-4:30pm west of NYC, 4-5pm over NYC, and 4-6pm over Long Island and southern CT. Enhancement of the snow bands is likely over southern CT as the coastal low intensifies, with the highest storm totals expected to be situated over that part of the area. Storm total accumulations of at least 2-4 inches are still expected across most of the area except for coastal locations where mixing with rain and/or sleet has occurred, with at least 4-5 inches of snow likely over southern CT, locally higher for some areas.

The model guidance, despite remaining fairly consistent with its handling of this system, did not handle some aspects correctly, such as this morning’s round of snow which was lighter and much faster than expected. There are two shortwaves associated with this system, one that passed through the Great Lakes this morning at 500mb, and the other following behind it over the Ohio Valley, with the back shortwave trough swinging through the region tonight while amplfying and becoming negatively tilted. The leading shortwave was originally modeled to be somewhat weaker and more progressive, quickly taking it trough the region in the morning with the trailing shortwave trough unable to amplify as much, preventing significant amplification of the trough and development of a stronger storm. In the short range, however, the models trended towards a slower and more amplified leading shortwave and a more amplified trailing shortwave trough, leading to a weaker front end snow scenario and the development of a stronger coastal low closer to the coast later in the day.


9:50 AM: Coastal Low To Develop Soon

nerad25[1]Since the last update, snow has fell across the area with accumulations up to at least an inch recorded, although the first round of snow has moved out much earlier than expected. The coastal low is expected to develop near the coast early this afternoon, intensifying as it tracks towards Maine; additional precipitation is expected to develop after at least 11am-12pm with more widespread snow likely, with additional moderate snow possible towards the mid afternoon hours on the western end of the low pressure before snow ends late in the afternoon or in the evening.

Storm updates will be temporarily paused for now; more frequent updates will resume after 12:30 to 1pm.


5:45 AM: Snow Approaching

12.17_1030As a weak Alberta clipper system enters the region, snow has started to develop across northern New Jersey, and will spread into the rest of the area by 7-7:30am. Moderate snow is expected with the onset of the storm, and will continue through at least 12pm in northern NJ/NYC and 1-2pm in Long Island/CT.

Uncertainty increases this afternoon regarding the coastal low development, however. Originally, clearing conditions were expected after 12pm with a few isolated snow showers. Based on the latest data from the short range models, however, snow may persist into the mid afternoon hours with the coastal low developing closer to the coast and intensifying earlier than initial projections. Most of the snow accumulations are expected before noon, although additional light accumulations may be added afterwards.

The forecast is for 2-4 inches across most of the area, except for southern Long Island, where the proximity of the low pressure bringing a stronger onshore southeasterly flow will lead to temperatures rising into the 30s and possibly low 40s, resulting a changeover to rain after this morning with at least 1-2 inches expected prior to the changeover. At this time, snow is expected to persist until at least 2-4pm before ending from SW to NE, although a few changes may be possible.

Today’s update schedule: The next update will be posted at 9:50am, followed by another update at 1pm.

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