Frequent updates will be posted below on the heavy snow event affecting the region today. Radar images are from the National Weather Service and the Pennsylvania State University e-Wall.
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Final storm snow totals in NYC: (Updated 7am)
Central Park – 12.5″ | LaGuardia – 10.9″ | JFK Airport – 6.9″
8:25 AM: Snow Over, More On The Way
The regional radar as of 6:15am has been posted to the left, showing the snow as it ended across the area. Following the initial thunderstorms late yesterday evening, a gradual changeover to snow occurred from west to east with a period of moderate to heavy wet snow through at least 3-5am, but with warmer surface temperatures near 32-34 degrees. The heaviest snow last night stayed west and north of the area, which was further west than anticipated, although up to 1-2 inches were observed in most of Long Island/CT with totals between at least 2-5 inches or locally higher from NYC and further north/west.
According to the storm reports posted by the National Weather Service, this storm was the most significant snowstorm of the winter across the region, and has further solidified this winter’s status as much snowier than average, and in some locations entering the top 10 list of all time snowiest winters on record. With 12.5 inches in Central Park, the winter snow to date total is 54 inches, placing it as the 9th snowiest winter on record, behind 1960-61 with 54.7 inches. The snowiest winter on record was 1995-96 with 75.6 inches. Elsewhere in the area, snow totals were generally between 6-10″ in the eastern coastal locations and over 10 inches elsewhere, with the highest totals in the lower Hudson Valley. The highest storm report so far is 20.5 inches in Harriman, NY (Orange). Along with a wide variety of impacts ranging from intense snow rates over 4″/hour in Long Island to heavy thunderstorms last night, including a broad coverage area extending from the southeast US to Maine, this storm is likely to be remembered as a highlight of the winter of 2013-14.
This is the final storm update associated with this system; more snow is on the way, however, as another strong coastal low pressure is expected to develop off the coast tomorrow, producing another round of snow, with light to moderate accumulations for most locations but with heavy snow possible again in eastern parts of the area. The next forecast discussion will be posted by later this afternoon discussing tomorrow’s outlook more in depth.
11:00 PM: Changeover To Snow Occurring
Over the last two hours, a band of heavy thunderstorms moved through the area, with precipitation type falling as rain/sleet in Long Island into NYC and southern CT and sleet further inland, but has gradually began mixing with snow over the last half hour in parts of Long Island and NYC. A small dry slot has moved into central NJ, with occasional snow/sleet continuing in northern NJ, but with precipitation type to gradually change to snow over the next 2 hours as the mid level low moves through and the column cools down. As the snow over eastern PA pivots into the area, additional moderate to heavy wet snow is expected, with the heaviest rates towards NW NJ and SE NY where snow totals of 5-9 inches are expected with locally higher totals. Further southeast, precipitation rates may not be as heavy, especially with the snow band having set up west of the forecast, but with a slight bust potential remaining for totals slightly higher/lower than forecast. Current thinking is up to 3-5″ in the N/W suburbs of NYC, 2-4″ in NYC and W CT, and less than 2″ east of NYC and elsewhere in CT.
Saturday Outlook: Another Snowstorm Possible
Despite this being a storm update post, the latest trends have been concerning enough to make a mention of the updated outlook for Saturday with regards to another potentially significant snowstorm for parts of the region. The model guidance has significantly changed its handling of a strong shortwave trough, which now digs more and becomes negatively tilted further west, supporting a strong coastal low pressure developing east of the area with widespread light to moderate snow. The latest models depict general 1-3 inch totals across most of the area with totals over 3 inches in eastern parts of the area, although the latest runs continue to come in further west and more amplified. At this time, a widespread 1-3 inch snowfall appears likely with higher totals possible in eastern Long Island and SE CT, with heavier snowfall into eastern New England, although this time frame will continue to be closely monitored, with continued western adjustments on the model guidance potentially introducing snow totals near or over 6 inches into eastern parts of the area.
8:45 PM: Rain, Sleet, Snow Moving In
The dry slot has gradually filled in as the mid level low is approaching from Virginia, with a line of heavy rain, sleet and thunderstorms currently over central NJ, progressing north. This line is expected to enter the area between 9pm and 9:30pm, with heavy rain and thunder east of NYC, possibly including NYC initially, and heavy sleet and possible thunder from NE NJ and further north/west. The changeover timing remains unchanged from the earlier update, but with the short range models shifting slightly west with the placement of the heaviest banding tonight, which does not appear unreasonable given the current radar trends. The higher accumulation and snow rates are likely to be confined to north central/NW NJ and the Hudson Valley region, with locations from eastern NE NJ and eastward likely to observe heavy sleet through at least 11pm-1am before changing to snow, but with the heaviest precipitation having passed to the north, with a period of moderate to heavy wet snow possible especially in the north/west suburbs of NYC, including the city and western CT, but with lower accumulations than locations further inland, with 2-5″ currently likely in these locations into W CT and less than 2 inches for the rest of Long Island into south central/SE CT.
6:55 PM: Second Round To Begin Shortly
As the mid level low continues to track northeast, thunderstorms have developed over Maryland as cold air aloft begins to filter back in behind the low, leading to a changeover to heavy snow and sleet with occasional thunder. To the east of the main banding, a line of heavy rain squalls and thunderstorms has developed over southern NJ, and is steadily tracking north; heavy precipitation is expected to return to most of the area between 7:30 and 8:30pm, except for eastern Long Island and CT which may see lighter precipitation. From NE NJ and further east, this is expected to be in the form of plain rain and heavy thunderstorms, while the rest of New Jersey and SE NY are expected to observe heavy sleet with thundersleet possible.
The mid level low will pass through or just east of NYC towards 10pm-12am; the changeover back to snow appears to take longer than earlier thought, and is currently forecast to occur between 9-11pm west of NE NJ, 10pm-12am in NE NJ and SW CT, and after 12am-1am from NYC and further east. As a result, a fair amount of the heavy precipitation is likely to be spent as heavy rain/sleet from NYC and further east, preventing major snow accumulations. Meanwhile, the changeover is likely to occur early enough to support heavy snow towards north central and NW NJ into the Hudson Valley, with thundersnow possible along with snow rates up to or possibly over 2 inches per hour. Snow is expected to end by 3-5am from SW to NE.
The latest updated snow outlook for tonight only is 5 to 8 inches in NW and north central NJ into SE NY, locally higher; 2 to 5 inches in NE NJ, NYC and SW CT; and less than 2-3 inches in Long Island and through the rest of SE CT.
3:55 PM: Dry This Afternoon; Round Two Approaching
Over the last three hours, the heavy snow banding shifted to the north of the area as enough warm air aloft and near the lower levels entered the area to result in a changeover to rain for Long Island, NYC and southern CT, with light snow and sleet continuing to fall inland. With drier air in the mid levels, generally dry conditions are expected to continue through the next few hours while temperatures are warm enough to support rain and/or sleet, mostly in the low to mid 30s, preventing a significant washout and melting of the snow.
The second round can be seen over Virginia in association with the mid level low, which will continue to track NNE through the rest of the afternoon and evening. The mid level low will reach the New Jersey coast later this evening, with heavy precipitation expected to develop across most of the area after 7-9pm, mainly west of central-western Long Island and CT. Initially, this is expected to fall as rain in NE NJ, NYC and CT, with the possibility of thunderstorms as well. As winds aloft turn northerly and temperatures begin to cool down again, a gradual changeover back to snow is expected from west to east between at least 9pm and 11pm. The heaviest snow at this time is expected to set up over northern NJ into SE NY, where snow rates up to 2-3 inches per hour and thundersnow are possible, accumulating up to 5-10 inches. Further east, at least 2-5 inches are likely in NYC and western Long Island/W CT, and up to 3 inches in the rest of Long Island and central-eastern CT. The exact positioning of the banding is subject to slight changes, and may be a little east of the current forecast.
12:20 PM: Dry Slot Moving Through
As of 12pm, the low pressure is just southeast of Delaware. Minimum pressure is near 993mb, and the low continues to track NNE up the coast. The 500mb trough axis is centered near South Carolina, with the SPC Mesoanalysis indicating a closed 500mb low near south-central North Carolina.
Since the previous update, very heavy snow continued to fall across Long Island, NYC and coastal CT, with the National Weather Service at Upton making note in their earlier discussion of snow accumulations between 3-4 inches in just half an hour. Snow reports as of 11am across the area were generally between 7-13 inches in Long Island, and 5-10 inches across the rest of the area. Since then, however, warm air advection has continued aloft as the 850mb low, still southwest of the area, continues to gain more of a south-north orientation as the mid-level trough axis becomes negatively tilted, supporting the rain/snow line continuing to advance inland, with most of Long Island and NYC currently reporting rain and/or sleet. Locations further inland are still reporting snow, but withe mixing line to continue spreading inland at a somewhat slower rate over the next few hours, with most locations except for far NW NJ and interior SE NY likely to change over to rain and/or sleet at some point.
Despite the anticipated relatively long duration of temperatures near or above freezing, in some ways this can be considered a mainly snow event as drier air in the mid levels works its way in from the south, with the heavy precipitation expected to move north of the area over the next 1-2 hours. Conditions will not be dry the entire time, but with scattered rain and/or sleet showers expected to continue for most locations through the afternoon hours, with somewhat steadier light snow/sleet towards NW NJ and interior SE NY. Some melting of the snow is likely in this time period but with no significant melting likely. Towards 7-8pm, additional heavy precipitation will develop as the mid level low moves nearby or slightly to the east, with winds aloft turning northerly supporting a gradual cooling of the column and a changeover back to snow from west to east. Precipitation may begin as rain/sleet from NE NJ and further east, gradually changing back to snow after at least 9-10pm. The heaviest snow at this time is likely to focus across eastern PA into NJ, NYC and the Hudson Valley into western Connecticut, with an additional 4-8 inches of snow possible. Thundersnow cannot be ruled out as well. At this time, forecast totals remain unchanged besides from Long Island, where totals of 8-13″ are expected, locally up to 15 inches in western areas.
9:40 AM: Snow Totals Exceeding Forecast In NYC, LI
As of 9am, the low pressure is east of SE Virginia. Minimum pressure is near 996mb, and the low continues to slowly track to the NNE. The 500mb trough axis is extending into Georgia and South Carolina, and will continue to become increasingly negatively tilted today before closing off as it approaches the area tonight.
Impressive snow rates have continued over NYC and Long Island over the last few hours, with snow rates up to 3-4 inches per hour reported. The latest radar depicts a strong band of 50-55dBZ reflectivity entering Long Island and NYC, which may possibly be mixed with sleet but is expected to feature additional heavy snow rates up to 3-4 inches per hour over NYC and Long Island. Locations further east continue to see heavy snow but with lighter rates, up to 2″/hour in NE NJ and 1″/hour elsewhere in the area. Behind this band, sleet is expected to begin mixing with snow across a larger coverage area into 11am-12pm over Long Island, gradually extending into NYC, NE NJ and southern CT by 1-3pm as precipitation begins to decrease in intensity.
The latest high resolution models continue to shift north and west with the heavy banding setup for tonight, keeping the heaviest snow near west-central New Jersey into the Hudson Valley. At this time, the outlook remains unchanged for tonight, with an additional 3-7 inches of snow likely in New Jersey into NYC, SE NY and western CT with the possibility of rain/sleet mixing initially and isolated reports of thundersnow, although the positioning is subject to some changes.
Snow Forecast Update: With the latest observations, the snow outlook has been updated to 7-14 inches in Long Island, 7 inches being further east and 13 inches further west; 9 to 15 inches in NYC and southern CT; and 10-18 inches across northern NJ and SE NY, as well as parts of southern CT, with a narrow axis of 14-18 inch totals likely somewhere between north central NJ and NYC depending on the setup of the heavy snow tonight.
8:00 AM: Heavy Snow Entering NYC, LI
As of 7am, the low pressure is just east of SE Virginia. Minimum pressure is near 998mb, and the low pressure is steadily tracking to the NNE. Additional deepening is expected below 990mb as the low slowly continues NNE, positioning itself east of New Jersey later today into the evening hours.
The heavy snow banding has continued to lift northeast along with the most favorable dynamics, with the heavy snow band currently over NYC and Long Island. The band will continue to extend north over the next 1/2 to 1 hour with heavy snow covering the entire area, except for perhaps interior SE NY. The heaviest snow rates are expected from NE NJ and further east into NYC, LI and southern CT, with rates of 2-3 inches per hour expected through 11am-1pm, when the mixing line will begin to extend into coastal Long Island and eventually reach NYC, NE NJ and southern CT by 1-3pm. A period of drier conditions is expected from about 2-3pm through 7-9pm with some drier air entering in the mid levels around 700mb and with the stronger lifting shifting to the north and NE, placing the area under some subsidence. This drier period will coincide with the timing of the warmer temperature columns favorable of supporting rain, leading to only scattered light to locally moderate rain/sleet showers through the rest of the afternoon and evening hours, likely remaining as snow in NW NJ and interior SE NY, where somewhat steadier precipitation is expected than the rest of the area.
The main difficulty remains with the positioning of the overnight round of snow; the global models generally indicate this will set up from NYC into Connecticut and Massachusetts, while the high-resolution RGEM, RAP and 4k-NAM place the heavier snow from New Jersey into the Hudson Valley and western CT/MA, with light rain/snow continuing east of NYC. Considering that the RGEM has been too amplified with the storm, and the RAP often tends to end up too far north and/or amplified in its longer range, the latest outlook is for the heavy snow to set up over most of central-eastern NJ into NYC, SE NY and western LI-CT, possibly starting out as a period of rain/sleet, with the possibility of thundersnow and additional heavy snow rates potentially accumulating up to 3-6 inches. This axis is subject to some changes later today.
5:45 AM: Heavy Snow Approaching, 2-3″/hour Rates
As shown in the latest radar to the left, light snow has spread across the area, with intensifying moderate snow rates entering the southern parts of the area. SPC Mesoanalysis indicates very strong 700mb frontogenesis between Washington DC and southern NJ with continued mid-level warm air advection, aligned well with the heavy snow banding currently in place. The snow rates from these locations, however, have even exceeded the expectations of 2″/hour rates, with widespread reports of near or over 3″/hour snow rates under the heavy banding. As such, snow totals have overperformed in these locations, with snow totals already in the 12-15 inch range in Virginia into Maryland.
Forecast Update: The higher frontogenesis values will continue to extend northeast, reaching the area by at least 7-8am. This will place the entire area under heavy snow rates over 1-2 inches per hour, with the heaviest banding capable of snowfall over 2-3 inches per hour from about north central NJ east into NYC and Long Island; while mixing with rain is anticipated near the coast of Long Island beginning by 11am-12pm, enough snow is expected to fall initially to offset the longer duration of mixing relative to the rest of the area. The heavy snow is expected to continue until 12-2pm while the temperature column warms up enough to support rain/sleet, but with dry slotting expected through the evening hours resulting in only scattered light rain/sleet showers, likely persisting as snow in north central/NW NJ and interior SE NY.
The biggest uncertainty for today remains the handling of the comma head snows this evening as the mid level low passes to the east and the surface low pressure center repositions itself east of New Jersey and continues northeast while rapidly deepening, supporting the formation of additional heavy precipitation banding. At this time, I am siding with the further south/east models with the handling of this feature, with heavy precipitation expected again between 8-9pm and 2-4am. This may start out as rain/sleet especially from NE NJ and further east, but with the rain/snow line shifting east as winds aloft turn northerly with the mid level low passing to the east, supporting a cooling of the temperature column. The heaviest snow is favored over New Jersey into NYC, SE NY, and western Long Island and CT. The exact accumulations are tough to narrow down, although at least an additional 2-5 inches of snow are expected from this round at this time.
With the above noted, including the overperforming snow rates and accumulations in the Mid Atlantic, the updated snow outlook is for 5 to 10 inches of snow in Long Island, 8 to 14 inches in NYC into SE CT, and 10 to 16 inches over northern NJ, SE NY and the rest of CT, with locally higher totals possible.