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New York, NY

January 26-27th 2011 Heavy Snow

Summary: A high impact winter storm produced 1 to 1/1/2 feet of snow across the County Warning Area (CWA) Wednesday and Thursday, January 26-27, 2011. Over 19 inches of snow accumulated in Central Park. Mayor Michael Bloomberg declared a weather emergency for New York City. Bloomberg announced the closure of all non-emergency city government offices and New York City Schools were closed. The storm broke New York’s record for January snowfall. A total of 36 inches had fallen in Central Park this month compared with 27.4 inches in 1925.

Snow accumulations caused massive transportation delays including over a thousand airline cancellations at all of the major New York airports. John F. Kennedy International and Newark Liberty airports were closed until 1030 a.m. and 9 a.m., respectively, according to the Federal Aviation Administration. Amtrak suspended its passenger rail service from New York to Boston and cut service between New York and Albany.

There were several synoptic players in this prolific snowstorm. In the top left panel...pacific and subtropical jet energy phased together over the Deep South with a 125+ kt upper jet streaking up the Atlantic coast...placing the region in a favored left front quadrant. This subtropical connection played a role in the early start to snowfall on Wednesday morning and heavy precipitation Wednesday evening. It also enhanced the strength and depth of lift of subtropical moisture over the region and allowed for rapid intensification of mid and low-level low pressure as it tracked just southeast of the region. In the top right panel...the rapidly deepening closed mid-level low tracked over the region providing instability and strong lift across the region. In the lower left panel...strong low to mid level frontogenic and deformation forcing...combined with instability aloft...resulting in heavy snow banding and embedded thundersleet and thundersnow across the region. In addition...a tongue of warm air intruding on the region at this level Wednesday afternoon into Wednesday evening brought a period of sleet and freezing rain to the city and coast. In the lower right panel...double barreled surface low pressure tracked up from the Gulf of Mexico to the Carolina Coast on Wednesday and then rapidly intensified as it tracked just southeast of Long Island Wednesday night in repsonse to the aforementioned intense upper energy.

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


The following sounding depicts the steep mid-level (700-500 mb) lapse rates and elevated cape that developed Wednesday evening as the upper low tracked towards the region. The available instability facilitated the development of prolific thundersleet and thundersnow. In addition...a hint of a nose of warm air can be seen at this time at 850 mb. This warm layer increased for a period in the evening along the coast...allowing for a mix of heavy rain, sleet and freezing rain...before changing back to heavy snow in the late evening and overnight as cold air wrapped back in behind the deepening low.

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OKX 01/27/2011 00Z 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...a vigorous mid level low can been seen rotating through the Tennesse River Valley towards the Mid Atlantic Coast and then southeast of Long Island as the strong phased upper jet (yellow/orange) rounds its base. Ahead of the jet...a plume of moisture is evident streaking north from the subtropics. The abundant thunderstorm activity within this moisture plume may have played a contributing factor in the inability of the models to properly resolve the extent of the moisture feed into the region. On the IR imagery to the right...note the rapidly cooling cloud tops (red) in two batches. The first area coincides with the subtropical moisture plume being lifted ahead of low pressue and up and over its associated warm front. This was responsible for the snowfall Wedneady morning into early afternoon. Then a period of warmer clouds (yellow) over the region Wednesday afternoon and early evening coincided with the lighter wintry mix during that time. Then a second area of strongly cooling cloud tops can be seen working across the region Wednesday evening into Wed night on the backside of low pressure. This is coincident with the strong deformation/frontogenetic banding ahead of the strong mid/upper level low...which is when the strong upward vertical motion of moisture and elevated instability came together to produce heavy precipiatation with embedded convection.

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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. A period of moderate to heavy snow overspread the region Wednesday morning intoWednesday afternoon in response to a subtropical moisture feed ahead of Mid Atlantic low pressure and over an associated warm front to our south. Then after a period of a light wintry mix late Wednesday afternoon into early evening...explosive development of heavy precip (yellow/orange) and convection can be seen working north towards the region from the Mid Atlantic/Delmarva area. This was in response to the lift/instability of the upper low working towards the region and intensifying coastal low pressure throwing moisture back over the region as it tracked southeast of the region. As this area of heavy precip and convection worked north into the cold air over the region...a very heavy snow band developed over Northeastern NJ, the NYC Metro, Southern and Eastern Portions of the Lower Hudson Valley, Northern and Western Long Island and Southern Connecticut...gradually pulling northeast through Wednesday overnight. This band was responsible for snowfall rates of 3 to 4 inches per hour over a 4 to 6 hr period...and raising snow totals to 15-20 inches across much of the region.

Radar Loop


Post-storm Snow Depth and Snow Water Equivalent
Following 3 to 4 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 28th 12z
Total Snow Water Equivalent as of January 28th 12z
Map of Total Snow Depth as of January 28th Map of Total Snow Water Equivalent as of January 28th


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 31, 2011
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