Forecast: Clearing, but cold & wintry pattern ahead

GFS Model showing below normal temperature departures throughout the majority of the United States through the first week of Spring. Image courtesy Ryan Maue and Weatherbell.

GFS Model showing below normal temperature departures throughout the majority of the United States through the first week of Spring. Image courtesy Ryan Maue and Weatherbell.

Rain and snow lingered through the area on Tuesday morning, in the wake of a storm system which dropped a few inches of snow in most locations before a changeover to rain occurred Monday Night into Tuesday morning. Some snow still remained on the ground (and roads) but rain and the presence of some sun later today should help to melt whatever is left, aside from the areas across the interior which accumulated several inches of new snow. The bands of snow and rain are expected to pull away from the area by the afternoon hours on Tuesday, with clearing reaching the area by late afternoon. West winds and some sun could allow temperatures to reach into the middle 40’s on Tuesday afternoon.

The winds will strengthen Tuesday into Wednesday and could become quite breezy at times, with gusts to 30 miles per hour as the new cold airmass enters the area behind the storm system. All eyes will then turn to the potentially wintry pattern towards the end of the week into the weekend. The first system of interest comes as early as Wednesday Night into Thursday, with a weak low pressure system forming offshore. Some light rain or snow is possible along the coast as the storm develops well out to sea  and a weak inverted trough passes over the area. No accumulations are expected.

Almost all forecast models show a low pressure system on the East Coast this weekend.

Almost all forecast models show a low pressure system on the East Coast this weekend.

The second, and likely more impactful, potential system won’t impact the area until later this weekend. A strong disturbance will eject out of the Pacific Northwest into the Central United States by Saturday — and then track eastward towards the East Coast by Sunday and Monday. Uncertainty still exists in regards to exact track and strength of the disturbance. Most notably, an upper level low to the north of our area is very important in determining where the system will eventually track. An upper level low farther south over New England will act to suppress the storm, while one farther north will allow the system to come up the coast. In addition, the exact positioning of the strong blocking (discussed in previous posts) will have an impact on the eventual strength of the surface low pressure as it nears the area.

Regardless of exact track, forecast models are in good agreement on an eventual low pressure system passing somewhere to our south off the East Coast late this weekend or early next week. The details should be ironed out over the coming days, and we’ll be sure to keep you updated.

PM Forecast: Period of wintry weather through Tuesday AM

Snow was falling early Monday evening throughout most of the area, and was expected to continue for a few hours. Precipitation will change over to rain with time and continue into Tuesday morning.

Snow was falling early Monday evening throughout most of the area, and was expected to continue for a few hours. Precipitation will change over to rain with time and continue into Tuesday morning.

A storm system tracking to our north and west will redevelop off the New Jersey coast and south of Long Island tonight, bringing steady precipitation to the area overnight into Tuesday morning. Warm air advection (increasing presence of warm

NYMetroweather snowfall forecast through Tuesday at 12pm.

NYMetroweather snowfall forecast through Tuesday at 12pm.

air in the atmosphere) will begin in the evening, changing precipitation from snow to sleet and rain from southwest to northeast with time. However, a period of snow and sleet is likely even near the coast. Across the interior, several hours of snow and sleet are expected to bring moderate accumulations. Travel could become difficult overnight tonight, especially across the elevated interior areas. Eventually, precipitation is expected to change to all rain throughout the area by Tuesday morning before ending. Total snowfall accumulations of 1-3″ on cold surfaces are expected in Northeast NJ, NYC, and Long Island. Mainly wet roads are expected in the city. Across the interior, 3-6″ of snow/sleet is possible before the changeover to rain.

Although we opted not to issue a Storm Alert Brief due to the short-fused nature of the travel difficulties, our storm total snowfall forecast is available…attached to this post. The official 3 day forecast is also included below. After the storm system on Tuesday, attention will turn to a potential winter storm next weekend which has become a feature on almost all medium range forecast model guidance. Stay tuned.

Tonight: Periods of snow and sleet, changing to rain. Low near near 32, colder inland. East winds 10 to 20 miles per hour, gusting near 30 miles per hour.

Tuesday: Rain likely in the morning, then clearing. High near 47. Northeast winds turning west in the afternoon around 15 miles per hour.

Tuesday Night: Partly cloudy, with a low near 30. West winds around 15 miles per hour, gusting to 25 miles per hour.

Wednesday: Sunny and breezy, with west winds around 20 miles per hour. High near 45.

Sunday AM Update: Wintry pattern looms

The RGEM model shows moderate snow in the NYC area at 5 p.m. Monday

The RGEM model shows moderate snow in the NYC area at 5 p.m. Monday

The NAO blocking has arrived, and much of the area saw periods of snow during the day on Saturday, enough to remind us that winter is still holding its grip on us, despite the calendar turning towards Mid March. We are also following the potential for two storm systems; one for Monday evening through Tuesday morning, and another one as we approach the March 24 period. Monday evening through Tuesday morning looks more rainy and messy than snowy, though further northwest of the city might be able to hold onto enough cold for minor snowfall accumulations along with some ice. However, March 24 is a period that needs to be watched for more serious snowfall potential, albeit it is quite far away, so caution should still be urged.

A stronger storm system will be developing to our west, as energy enters the United States from the Pacific Ocean. Considering we have a decently cold airmass in place right now, the precipitation that moves into our area could start off as snow, as warm, moist air overruns the cold air in place. If enough solid precipitation can break out to the east of the storm system, then we might see precipitation before the warm air advection would settle in. The RGEM model illustrates this well, as it shows a several hour period of snow for the NYC area, and then turning over to sleet.

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High latitude blocking may set up a cold finish to winter

GFS Ensembles showing 500mb height anomalies well below normal across the Northeast US by next week in response to blocking developing in Greenland and Northern Canada.

GFS Ensembles showing 500mb height anomalies well below normal across the Northeast US by next week in response to blocking developing in Greenland and Northern Canada.

It may be a bit premature to say that Spring will be off to a cold start. Medium and long range forecast guidance, however, would say that is a fair forecast. Forecast guidance has been pointing to the development of a very strong high latitude blocking episode within the next week, which could include a NAO and EPO ridge. The combination of the two could force a piece of the Polar Vortex (and very cold arctic air) into South-Central and South-East Canada, meaning our chances of below normal temperatures would increase … especially the farther north you go.

It seems, at least to the meteorologist, that there is a bit of an underlying passiveness towards March snowfall events in the New York City Area. I guess this comes somewhat naturally due to the past several years, which have offered very little hope for March snowfall (running well below normal in our area over the last 5-10 March’s). In fact, last year around this time much of the area saw temperatures soar into the 70’s for highs. Lets face it, March has been a nonexistent winter month in our area with the exception of a storm in 2009 which produced significant snowfall in parts of the area.

GFS Ensemble forecast Arctic Oscillation readings.Notice the rapid dropoff over the next week.

GFS Ensemble forecast Arctic Oscillation readings.Notice the rapid dropoff over the next week.

With all of that said, most of you are probably asking yourself: Why would it suddenly get cold and potentially snow this March? What makes it so much easier this time? The answer is that it won’t be that much easier. It still will be more difficult to get snow this time of year given the longer days, stronger sun, and warmer ground. But it is important to remember that forecast guidance has been strongly pointing towards the potential for a significant blocking episode — not just a run of the mill Greenland block or positive height anomaly. We can begin to see this response just glancing at the Arctic Oscillation forecasts, with remarkable ensemble agreement on the AO readings falling off the proverbial cliff. Almost every ensemble member brings the Arctic Oscillation below -4 and some of them to -5 — this is not your basic – AO development. It’s worth noting, too, how much lower these readings are compared to even the lowest readings of the past few months. A word of caution though, we should carefully watch the AO over the next several days as it has outrun the 7 day ensembles forecast in a positive direction recently (bottom chart).

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