WINTER STORM SUMMARY FOR
JANUARY 26, 2011 TO JANUARY 27, 2011 EVENT

Synopsis

An area of low pressure started to take shape off the Texas coast in the Gulf of Mexico on Monday January 24th. This area of low pressure slowly began to strengthen and eventually moved inland as it trekked up through the Southeastern United States on Tuesday January 25th. As the low deepened, energy was being transferred to a weak surface wave off the coast of North Carolina early Wednesday January 26th. This coastal wave started to produce precipitation over the Southern Delmarva shortly after 2AM on Wednesday the 26th and quickly spread to the north during the early morning hours. By noon, areas south of Philadelphia were experiencing a brief respite in the precipitation action, but another dose of winter weather was quickly approaching from the southwest.

The second wave of action came in fast and heavy starting around 4pm across the Delmarva, brought on by the parent low pressure system sitting over Southern Virginia. As the low moved towards the coast more energy was transferred to the slow moving coastal low and heavier precipitation started to spread further north and east. The coastal low finally started to wind down early on Thursday January 27th from west to east, eventually pulling far enough to the northeast to no longer have an affect on the region by mid-morning.

Watches/Warnings/Advisories

At 406AM on Tuesday January 25th, the first Winter Storm Watch was issued for the following areas: Sussex, Warren, Morris, Hunterdon, and Somerset in New Jersey; Carbon, Monroe, Berks, Lehigh, Northampton, Bucks, and Montgomery county in Pennsylvania. At 1120AM on the 25th, the Winter Storm Watch was expanded to include the following areas: New Castle and Kent in Delaware; Cecil, Kent, Queen Annes, Talbot, and Caroline in Maryland; Middlesex, Monmouth, Mercer, Salem, Gloucester, Camden, Burlington, Ocean, Cumberland, and Atlantic in New Jersey; Chester, Delaware, and Philadelphia in Pennsylvania. At 407AM on the 26th the Winter Storm Watch was upgraded to a Winter Storm Warning for the following areas: New Castle, and Kent in Delaware; Cecil, Kent, and Queen Annes in Maryland; Berks, Bucks, Montgomery, Chester, Delaware, and Philadelphia in Pennsylvania; Morris, Somerset, Hunterdon, Middlesex, Mercer, Monmouth, Burlington, Ocean, Atlantic, Camden, Salem, Gloucester, and Cumberland in New Jersey. Also at 407AM on the 26th the Winter Storm Watch was replaced with a Winter Weather Advisory for the following areas: Carbon, Monroe, Lehigh, and Northampton in Pennsylvania; Sussex and Warren in New Jersey. A brand new Winter Weather Advisory was issued at 407AM for the following areas: Sussex in Delaware; Cape May, and Coastal Atlantic(including Atlantic City) in New Jersey. At 1021AM the Winter Weather Advisory was upgraded to a Winter Storm Warning for the following areas: Cape May, and Coastal Atlantic in New Jersey; Talbot and Caroline in Maryland; Warren in New Jersey; Lehigh and Northampton in Pennsylvania. At 240AM on January 27th the Winter Storm Warning was canceled for the following areas: New Castle and Kent in Delaware; Cecil, Kent, Queen Annes, Talbot, and Caroline in Maryland; Warren, Salem, Gloucester, Camden, Cumberland, Atlantic, and Cape May in New Jersey; Berks, Lehigh, Northampton, Chester, Montgomery, Bucks, Delaware, and Philadelphia in Pennsylvania. The Winter Weather Advisory was canceled for the following areas at 240AM on the 27th: Sussex in New Jersey; Carbon and Monroe in Pennsylvania; Sussex in Delaware. At the conclusion of the event the Winter Storm Warning was canceled for the following areas at 340AM on the 27th: Morris, Hunterdon, Somerset, Middlesex, Monmouth, Mercer, Burlington, and Ocean in New Jersey.

Precipitation/Temperatures/Winds

As was stated above in the synopsis, light precipitation entered our region from the south shortly after 2AM on Wednesday January 26th and quickly spread towards the north. Heavier bands of rain were experienced across the southern Delmarva while further north and west a light snow began to fall. By 5AM, with the coastal low just offshore of the the outer banks of North Carolina, the heaviest precipitation, due to warm-air advection, was falling over central Delaware and southeastern New Jersey. At this time a moderate intensity rain was falling over central and southern Delaware with all other areas north and west seeing a light snowfall. With a stronger northeast wind blowing in off the Atlantic Ocean coastal areas in southeastern New Jersey along with most of the Delmarva had a change over from snow to moderate to light rain for a few hours during the late morning and early afternoon hours. This helped to keep the snowfall accumulation suppressed in these areas. All in all the first batch of moisture to be rung out over the region produced up to 6 inches across locales in southeastern Pennsylvania, with the highest amounts in Chester and Montgomery counties. Areas north of Philadelphia in New Jersey received an average of 2 to 4 inches with the highest amounts in Mercer, Hunterdon, and Somerset counties. This was just a taste of what was to come in the evening and overnight hours.

By 4PM on the 26th heavy precipitation was just to the west of the region. Frequent lightning was noted in southern Maryland and northern Virginia, due to atmospheric instability aloft. These strong areas of convection continued to move towards our region and by 5PM heavy rain and thunderstorms were seen over central Delaware. An inundation of sleet started to fall across southeastern New Jersey by 6PM and most areas recorded nearly an inch of sleet before changing over to snow. Numerous locations recorded thunder-sleet between 5PM and 7PM across central New Jersey, and even pea size hail was reported along coastal sections of Ocean and Monmouth counties! Meanwhile over in Pennsylvania the heavy sleet turned to all snow by 7PM in areas west of Philadelphia, while a mixing of snow and sleet still fell in the metro area. The entire region turned over to all snow by 9PM on the 26th. Thunder-snow was reported in Chester, Montgomery, and Bucks counties during the height of the storm. Snow-fall rates exceeded 4 inches an hour in some spots where very narrow mesoscale bands had set up and become nearly stationary for a couple of hours. These narrow bands produced copious amounts of snow that fell very fast and very hard across portions of the Philadelphia metro area and northern New Jersey. 

Over a foot of snow fell across portions of the region with the second batch of snow alone...quite a feat in only 9 hour time period. Occasional wind gusts of 25 mph were experienced across the region which, coupled with heavy snowfall, caused near whiteout conditions in some areas. The hardest hit areas of 16 inches or more were strewn across the region from Chester county in Pennsylvania northeast through Delaware, Philadelphia, Bucks, and Montgomery counties and then extended into Mercer, Hunterdon, Warren, Somerset, Middlesex, and Monmouth counties in New Jersey. There was one location in Gloucester county that reported over a foot and half, 19 inches, after the storm pulled out. Due to the mesoscale banding and mixed precipitation occurring over southeastern New Jersey and the Delmarva, snowfall accumulations in those areas were much less.

Significant Impacts/Aspects

This double whammy storm system caused numerous traffic delays during the morning work commutes on January 26th and 27th. Most schools across the region had an abbreviated school schedule on the 26th and were either closed or opened late on the 27th. Due to the ferocity of the snowfall generating near whiteout conditions, multiple interstates across the region had restricted speed limits and snow removal crews had a very tough time keeping the roads clear enough to safely pass. To make matters worse, the underlying layer of snow from the first batch of precipitation, combined with sleet at the start of the second batch, compacted into a layer of ice that was very difficult to remove from sidewalks and roadways after the storm was over. Public transit entities were still running on delayed schedules a full 24 hours after the event had concluded.

Notes

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