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New York, NY

January 11-12th 2011 Heavy Snow

Summary: A high impact winter storm produced as much as two and one-half feet of snow across the County Warning Area (CWA) Tuesday January 11-12, 2011. Interior Southern CT was the hardest with accumulations up to 30 inches. Eastern Long Island received 10 to 18 inches…with a few lower amounts across coastal Nassau County. NYC received 7 to 12 inches. Northern New Jersey and the lower Hudson Valley received 8 to 16 inches.

The highest snowfall totals were observed across Fairfield and New Haven Counties in Connecticut. The Governor of CT, Daniel P. Malloy, was cited as saying, “that the season's second major storm was a record-breaker, dumping more snow on Connecticut in 12 hours than the state had ever seen in a full day, up to 30 inches.”

In New York City, the snow arrived shortly before 9:00 pm Tuesday January 11, 2011, and heavy snow fell throughout the night. 9.1 inches of snow fell at Central Park, NY for the event which ended early Wednesday January 12, 2010. Mayor Michael Bloomberg says New York City's response to the latest bout of snow was very different than during the blizzard a few weeks ago. Bloomberg indicated the city's goal was the most effective snow response ever. A “Weather Emergency” was declared by NYC around 6 PM Tuesday evening. He declared the snow response a success in a news conference and credited the emergency declaration for helping to keep cars off the street. Regarding area airports, hundreds of international and domestic flights were on cancelled and postponed but delays were not as bad as during the Holiday Blizzard.

There were several synoptic players in this prolific snowstorm. In the top left panel...northern stream and southern stream jet energy phased together over the Tennessee River Valley with a 150+ kt upper jet streaking just south of the region. This enhanced the strength and depth of lift of Atlantic moisture over the region and allowed for rapid intensification of mid and low level low pressure as they tracked over and just southeast of the region, respectively. In the top right panel...the rapidly deepening closed mid-level low tracked over the region providing instability and lift across the region. In the lower left panel...a tight baroclinic zone and strong low level jet dynamics created strong frontogenic forcing...which combined with instability (EPV) aloft...resulted in heavy snow banding and embedded thundersnow across the region. In the lower right panel...surface low pressure tracked up the Atlantic seaboard and then rapidly intensified as it tracked just southeast of Long Island as it encountered the aforementioned intense upper energy.

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300mb loop 500mb loop
850-700mb Frontogenesis & EPV
850-700mb frontogenesis & EPV loop Surface loop


The following sounding depicts the steep mid-level (700-500 mb) lapse rates and elevated instability that developed Tuesday night as the upper low tracked into the region. The available instability facilitated the development of thundersnow.

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OKX 01/12/2011 06Z Upper Air Sounding
OKX 01/12/2011 06Z Upper Air Sounding


Satellite Imagery
The following are GOES satellite loops of the powerful storm system as as it affected the area. On the water vapor imagery to the left...note the vigorous mid level low rotating through the Ohio Valley towards the region...and the strong upper jet (yellow/orange) rounding its base...providing the deep lift and ample energy for the rapid intensification of the coastal low. On the IR imagery to the right...note the rapidly cooling cloud tops (red) ahead of the intensifying low pressure track...indicative of strong upward vertical motion of Atlantic moisture and embedded convective elements (multiple cloud to ground lightning strikes detected) coming together to produce heavy snow.

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Water Vapor Satellite Loop
IR Satellite Loop
Water Vapor Satellite Animation Infrared Satellite Animation


Radar Data:

OKX 0.5 Degree Reflectivity Data

The following is a base reflectivity RADAR loop from the KOKX WSR-88D with surface fronts and pressure overlayed. Note the explosive development of heavy precip bands (yellow/orange) off the New Jersey coast Tuesday evening...streaming north over the region (with occasional lightning strikes) as low pressure rapidly intensified. A dry punch of air is evident coming in across Long Island as low pressure tracks just se of Montauk Point. Then as the upper low worked over the region late Tuesday night a semi-stationary N/S band of very heavy snow developed just east of the Hudson River...gradually pivoting northeast Wednesday morning through early Wednesday afternoon. This band was responsible for snowfall rates of 3 to 4 inches per hour...and snow totals of 25-30 inches across Western and Central Connecticut all the way north into Southern Vermont. Residual bands of light to moderate snow continued across eastern portions of the region into the evening in the broad cyclonic flow around low pressure.

Radar Loop


Post-storm Snow Depth and Snow Water Equivalent
Following 2 to 3 major snowstorms since Christmas...a deep and moisture laden snowpack has been deposited across much of the Tri-State area.

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Total Snow Depth as of January 13th
Total Snow Water Equivalent as of January 13th
Map of Total Snow Depth as of January 13th Map of Total Snow Water Equivalent as of January 13th


National Weather Service New York, NY Watch/Warning/Advisory Products

The following Outlooks, Watches and Warnings were issued for this event by The New York, NY National Weather Service Office:

National Weather Service
175 Brookhaven Ave. Bldg. NWS-1
Upton, NY 11973

Page last modified: Jan 15, 2011
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