John Homenuk

Weekend winter storm to bring myriad of threats

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The National Weather Service issued Winter Storm Watches on Friday, in advance of a winter storm which is expected to impact the area this weekend. Forecast models have come into better agreement on the evolution of the storm system, which begins in the Central United States on Friday. The storm will track northeastward, as an initial disturbance moves towards the Mississippi Valley. The primary surface low will track towards the Ohio Valley by Saturday morning, before a compressed height field to the north and high pressure over New England force a secondary surface low to redevelop off of the Mid Atlantic coast.

Precipitation is expected to move into the area by late morning on Saturday, with snow beginning to pick up in intensity by early Saturday afternoon. Moderate to heavy snow is expected to continue through Saturday Night. But as warm air advection (the push of warm air towards the area in the mid and low levels via southerly winds) begins to pick up, snow will change over to sleet, freezing rain and quickly rain in areas like Southern New Jersey and Southeast Long Island. Southeast winds off the warmer area waters will not help to keep cold air locked in place along the coastal plain. But inland, deeper cold at the surface will hold on for a longer period of time – meaning a prolonged period of snow. With time, in the area suburbs, the warm air advection will push over the top of the cold air at the surface, changing precipitation to sleet and eventually freezing rain.

4km NAM simulated radar, showing a period of heavy snow throughout the area on Saturday before a transition to freezing rain and rain.

4km NAM simulated radar, showing a period of heavy snow throughout the area on Saturday before a transition to freezing rain and rain.

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John Homenuk

Weekend winter storm likely to bring various impacts

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A developing mid and upper level disturbance over the Central United States will slide eastward towards the Ohio Valley, and then redevelop off the Mid-Atlantic coast this weekend, providing a myriad of winter weather threats in our area When combined with the deep cold arctic air entrenched in the area upon its arrival, the storm seems likely to produce a fairly significant amount of snow and ice, especially away from the coast. But warmer air moving in aloft, and eventually at the surface, presents a forecast headache — as precipitation type will be difficult to predict until the event draws nearer.

Forecast model at this range are beginning to come into better agreement on the eventual track of the surface low associated with the mid and upper level disturbance. The initial (or primary) surface low seems likely to be driven from the Mississippi Valley into the Northern Mid Atlantic or Ohio Valley. But cold air, reinforced to the north, and associated with a strong high pressure system, and compressing heights aloft will force the storm to redevelop to the south and east off the Mid Atlantic coast before eventually scooting northeastward out to sea.

Canadian GGEM model showing the low pressure system off the Mid Atlantic coast with precipitation in our area, and a sharp gradient from snow to sleet and rain.

Canadian GGEM model showing the low pressure system off the Mid Atlantic coast with precipitation in our area, and a sharp gradient from snow to sleet and rain.

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John Homenuk

Cold, dry weather through weeks end

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After the first snowfall of the season on Tuesday, low temperatures fell into the single digits and teens throughout the area by early Wednesday morning. The arctic airmass settling into the area on Wednesday will stick around through the second half of the week, bringing high temperatures down into the upper 20’s and lower 30’s on Thursday. Although there won’t be any harsh biting winds, the snowpack over the interior will make it feel especially cold and will help with radiational cooling during the overnight hours. 850mb temperatures will fall to near -20 C on Thursday afternoon, and temperatures in the teens should be common each morning towards the end of this week.

The calm weather pattern will come as a bit of relief after several days of active weather with a front near the area. Owing to a dominant high pressure over the Northeast US, plenty of sun is likely on each day as we roll towards the weekend. But by the forthcoming weekend, intrigue will again increase as another mid and upper level disturbance tracks from the Central United States towards the Northeast and Mid Atlantic. As a result of this disturbance, a low pressure system is forecast to initially track towards the Ohio Valley. Eventually, a secondary low pressure will redevelop to the east, forced to do so by a strong high pressure to the north and cold air holding firm over New England. The devil is in the details with this system, as the uncertainties suggest potential for a winter weather event, but incredibly low confidence.

NAM model showing low temperatures in the teens on Friday morning.

NAM model showing low temperatures in the teens on Friday morning.

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John Homenuk

PM Update: Snowstorm winds down, cold air funnels in

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The first snowstorm of the year blanketed much of New Jersey and New York with a few inches of snow on Tuesday, leaving a wintry scene behind. Forecast snowfall totals were fairly accurate — with the general 2-4″ forecast throughout the area serving as a good indicator of what was to come. A brief burst of heavy snow early on Tuesday morning began the event which continued until the middle of the afternoon, before wrapping up as scattered snow showers. Some notable snowfall reports (still preliminary) include: Newark (2.2″), Kennedy Airport (2.0″), and Central Park (1.3″), all daily records for their locations.

A photo taken by Doug Simonian during the heavy snow burst at 10:30am in Rockville Centre, NY.

A photo taken by Doug Simonian during the heavy snow burst at 10:30am in Rockville Centre, NY.

We will post a separate article sometime tonight or tomorrow recapping the event which will have final snowfall totals, a photo gallery, and a brief analysis as far as what went right and wrong with the forecast. Although for the most part, the snowfall forecast verified, a few spots did not receive as much snow as they could have, due to surface temperatures hovering between 32 and 34 degrees, rather than in the upper 20s to around 30.

Tonight, as the storm system exits stage right, some serious cold air will begin to funnel into the area. Temperatures, both aloft and at the surface, will respond to this changing airmass and arctic intrusion — and the snow cover will help low temperatures plummet tonight. Overnight lows will fall into the teens across much of the interior and real-feel temperatures will fall into the teens in the city as well. Be aware of black ice potential on area roads, as any standing water may quickly freeze over. Wednesday morning will certainly be a shock to the system, and will feel quite wintry!

Today's 18z GFS valid for tomorrow morning shows low temperatures primarily falling in the teens in the interior, and low 20s in the city. Temperatures on Long Island will be a bit colder than what this model is showing -- probably in the low 20s as well. Image credit goes to weatherbell.com.

Today’s 18z GFS valid for tomorrow morning shows low temperatures primarily falling in the teens in the interior, and low 20s in the city. Temperatures on Long Island will be a bit colder than what this model is showing — probably in the low 20s as well. Image credit goes to weatherbell.com.

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