WINTER STORM SUMMARY FOR
FEBRUARY 21, 2011 EVENT

Synopsis

An area of low pressure, located over the Southern Plains, began to move towards the northeast early on Sunday February 20th. High pressure remained fairly entrenched across the Eastern Seaboard while a weak surface trough of low pressure extended from the east coast through the mid-west. An associated warm front extended east from the center of the low pressure while a cold front draped towards the southwest through New Mexico.

The high pressure started to retreat late on Sunday and allowed the warm front to near by very early Monday morning. Precipitation started shortly after midnight in Central and Southeastern Pennsylvania as a rain/snow/sleet mix, but eventually became all snow a few hours later and spread towards the northeast. By late in the morning the snow had come to end over the far northern counties where the largest accumulations had occurred.

Watches/Warnings/Advisories

At 332AM on Sunday February 20th the first Winter Weather Advisory was issued for the following areas: Carbon and Monroe in Pennsylvania; Sussex in New Jersey. At 412PM on the 20th the Winter Weather Advisory was upgraded to a Winter Storm Warning for Carbon and Monroe counties in Pennsylvania. Also at 412PM on the 20th the Winter Weather Advisory was expanded to include the following areas: Warren, Morris, Hunterdon, Somerset, and Middlesex in New Jersey; Berks, Lehigh, and Northampton in Pennsylvania; Sussex county New Jersey remained in the Advisory. At 829PM on the 20th the Winter Weather Advisory was expanded even further to cover the following areas: Chester, Bucks, and Montgomery in Pennsylvania; Mercer and Western Monmouth in New Jersey.

At 640AM on February 21st the Winter Weather Advisory was canceled for the following areas: Chester in Pennsylvania; Mercer, Middlesex, and Western Monmouth in New Jersey. Finally at 1026AM on the 21st, the Winter Weather Advisory was canceled for the following areas: Sussex, Warren, Morris, Hunterdon, and Somerset in New Jersey; Berks, Lehigh, and Northampton in Pennsylvania. The Winter Weather Advisory was allowed to expire for Montgomery and Bucks in Pennsylvania and the Winter Storm Warning was canceled for Carbon and Monroe counties in Pennsylvania.

Precipitation/Temperatures/Winds

The precipitation shield moved in late on Sunday night and slowly spread from the southwest towards the northeast continuing into the early morning hours on Monday the 20th. With a warm front providing a majority of the vertical lift and drawing moisture up from the south a mixture of rain/snow/sleet began to fall in the Philadelphia metro area. By about 1AM, more moderate precipitation bands were moving through SE PA and Central NJ and were generating a light snowfall accumulation. As warmer air aloft continued to move into the region from the south a changeover to a snow/sleet mix occurred a few hours later. Due to this changeover and the more moderate precipitation working its way towards the northeast, very light accumulations were experienced from I-195 southward with totals less than an inch. Heading further north, where the cold air was in place a lot longer and where the warm front never actually made it, snowfall amounts ranged from 3 to 6 inches in the Lehigh Valley and Northwest New Jersey...the highest amounts were seen in the higher elevations in Sussex and Morris in New Jersey and the Pocono Mountains.

Significant Impacts/Aspects

No major impacts were noted with this storm other than the usual traffic accidents associated with inclement weather. There were no reports of scattered power outages.

Notes

Information contained in this summary is preliminary. More complete and/or detailed information may be contained in subsequent monthly NOAA storm data publications.