Frequent updates will be posted below on the heavy snow and ice event affecting the region today. Radar images are from the Pennsylvania State University e-Wall.
Links: Yesterday’s forecast | 8-Day Forecast | Twitter | Facebook
Final storm precipitation totals in NYC: (Updated 2pm)
Central Park – 1.43″ | LaGuardia – 1.17″ | JFK Airport – 1.18″
2:35 PM: Precipitation Ending
As of 2pm, the low pressure is near north central PA; minimum pressure is near 1002mb, and the low is moving east. The coastal low pressure is south of Rhode Island; minimum pressure is near 1001mb, and the low is moving east-ENE.
Precipitation has mostly ended across the area, with isolated snow shower or freezing drizzle possible until the evening hours. The worst of the icing was avoided over northern parts of the area where more sleet was reported than freezing rain, but with more significant icing along and south of at least I-80 in New Jersey, especially in southwest parts of the area into western NJ and Pennsylvania, where widespread power outages have been reported. Temperatures are currently in the upper 20s inland and low to mid 30s elsewhere; this should allow for some of the snow and ice to slightly melt this afternoon and evening, but as the weakening primary low moves through the area late this evening, temperatures will crash overnight into the 10s inland and low 20s near NYC and the coast, leading to any melted snow and ice refreezing. Mostly sunny skies are expected on Thursday with highs in the mid to upper 20s for most of the area.
This is the final storm update for today. The next forecast update will be posted either tonight or early on Thursday morning.
10:45 AM: Precipitation To Gradually Weaken
As of 10am, the low pressure is near western Pennsylvania; minimum pressure is near 1005mb, and the low is tracking ENE. The coastal low is south of Long Island and east of Atlantic City; minimum pressure is near 1008mb, and the low is tracking ENE.
Based on latest reports, precipitation type remains as rain near coastal Long Island and NYC, freezing rain in parts of northern NJ and coastal CT, and sleet near far northern NJ into SE NY and interior CT. According to the storm total reports posted by the National Weather Service, snow totals in CT range from 3-5″ near the coast to 8-10″ inland; 4-7″ in northeast NJ and 5-10″ in NW NJ; 6-12″ in southeast NY; and 1-4″ in NYC and Long Island, including 4 inches at Central Park which brings the total winter snowfall so far to just over 40 inches. The heaviest precipitation has moved out of the area, although occasional light to moderate sleet showers in the north and light freezing rain/drizzle further south is expected to continue through about 2-4pm before mostly ending, with an isolated snow shower or freezing drizzle not out of the question until at least 8pm, when the weakening primary low tracks east through the area and offshore.
8:15 AM: Ice Continues Across Area
As of 8am, the low pressure is near extreme SW Pennsylvania; minimum pressure is near 1004mb, and the low is tracking ENE. The coastal low pressure is just southeast of Atlantic City; minimum pressure is near 1010mb, and the low is tracking NE.
Since the previous update, the mixing line has continued to spread slightly north, but with the northward advancement having slowed down near Rockland county into coastal CT. North of this line, heavy snow continues with snow totals exceeding the forecast, currently near 9-10 inches in the lower Hudson Valley into western CT; by the time the storm ends, snow totals up to 12-15 inches are likely in the lower Hudson Valley into interior southern New England, where the highest totals are likely from the storm. Further south, the southern coast of Long Island and coastal NYC have changed over to plain rain, with temperatures near 33-34 degrees. Elsewhere in the area, mixed precipitation continues; current reports indicate sleet is generally falling in far northern NJ into Westchester county and SW CT, and freezing rain further south.
Another batch of heavy precipitation is currently affecting the area, with precipitation types mostly sleet in northern locations, occasionally mixing with snow, and freezing rain to the south. The back end of the main precipitation shield is steadily advancing east, however, with steady freezing rain likely to begin weakening by 10-11am west of NYC and 12-1pm east of NYC. Occasional light freezing rain is expected to continue until about 2pm for most locations away from the coast before precipitation generally tapers off.
6:45 AM: Changeover To Sleet, Freezing Rain Beginning
As of 6am, the low pressure is near southeast Ohio. Minimum pressure is near 1005mb, and the low is tracking NE. The coastal low pressure is just off the coast of southeast Delaware; minimum pressure is near 1010mb, and the low is tracking NNE.
Since the last update, the intense banding has weakened over the immediate NYC area, with moderate precipitation continuing for most locations. The mid level low is currently over Ohio, with the area under moderate southerly winds aloft, supporting warm air advection in the mid levels as the warmest temperatures in the 850-700mb layer are currently near to slightly above freezing in northern NJ, NYC and Long Island. With the surface low to the south, however, surface winds remain from the northeast, essentially making it more difficult for the low level cold air to erode. With the mid levels warming faster than the surface, precipitation type has changed from snow to sleet and freezing rain in the earlier noted locations. Southern CT and SE NY remain with heavy snow at this time, but are expected to begin to mix with sleet by 7-9am. As model guidance often underestimates low level cold in situations similar to this one, precipitation type is expected to remain as sleet over NW NJ, interior SE NY and CT away from the coast, and freezing rain elsewhere except for the coastal regions in south/east Long Island and NYC, where a changeover to plain rain is expected soon.
In the freezing rain axis over central-NE NJ, northern NYC/LI, and coastal CT, ice accumulations of 0.25 to 0.40 inch are expected, with localized totals over 0.40 inch possible. This will lead to very hazardous road conditions, with downed trees and power lines possible leading to power outages. While snow totals cannot be determined to a full extent due to a lack of snow reports so far, snow totals of at least 7-12 inches are expected over interior SE NY into interior Connecticut where snow is still falling.
5:30 AM: Heavy Snow, Thundersnow In NE NJ, NYC
As of 4am, the low pressure was near the Kentucky/Ohio border. Minimum pressure is near 1007mb, and the low is tracking NE. The coastal low pressure is near southeast Virginia with a minimum pressure of 1013mb, and is tracking NNE up the coast.
Over the last few hours, snow spread into the area between 12-2am, gradually intensifying as heavy snow over Pennsylvania continued to extend northeast. Precipitation initially fell as sleet in some locations, but changed back to snow as a pocket of colder air aloft underneath the heavier precipitation moved through. Dynamics were very impressive with very strong mid level lifting and frontogenesis; these parameters were expected to support the formation of a heavy snow band between about I-80 in New Jersey into SE NY and CT. The heavy snow band that did form was not as widespread as anticipated, but was remarkable for extremely intense snow rates between about 3:45am and 5am as a convective snow squall moved over northeast NJ, NYC and SE NY; radar reflectivity values were as high as 50-55 dBZ, values often seen during summer thunderstorms. Snow rates up to 3-4 inches per hour were a common theme under this band along with numerous reports of thundersnow. Teterboro, NJ, which was underneath the band, reported 0.33″ of liquid-equivalent precipitation falling as snow in just one hour. This snow squall was so heavy that some radar precipitation-type algorithms, such as the one above from PSU e-Wall, misdiagnosed precipitation type as rain. The last time such intense snow rates were seen over the area from a synoptic storm system was during the February 8, 2013 blizzard in Connecticut.
Since then, the intense snow has let up over the immediate NYC area, but with moderate to heavy snow persisting primarily north of I-80, with mixing with sleet along and south of I-80 extending into NYC. There are not many snow reports as of 5am, although this band has verified the concern from yesterday’s update of more snow than forecast north of I-80; in some locations snow totals up to 4″ in NYC and 7″ in northern NJ have been reported; a clearer picture of snow totals from this intense snow band should emerge during the morning hours.
I am currently analyzing the impact this will have on snow totals across the area and will update this post shortly, although indications support the heaviest regional snow totals from the region setting up closer to the area (southeast NY & southern New England), rather than in central NY state as most of the model guidance indicated. An update will be posted on the icing situation as well.