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NYC Weekend Weather Update – Feb 15, 2014

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We will be feeling the impacts of yet another storm, in what seems like an endless winter. A low pressure system currently over Cape Hatteras will move offshore into the Atlantic shortly. Once it does so, it is forecast to strengthen rapidly as it moves northeast towards the 40N 70W benchmark, which is associated with prime conditions for growth of strong nor’easters and winter storms.

Currently, forecast models are showing the brunt of the storm hitting Southeastern Mass and New England. In areas, the NWS office in Taunton is confident that there could be up to 12-15″ of snow, in addition to strong winds in excess of 50mph that have led to blizzard warnings for east facing shores of Mass including the Cape.

Impact

For our area, eastern Long Island is expected to see enough of a heavy snow band forecast to rotate around this storm to have winter storm warnings issued. These areas could see 6-8″+ of snow from this storm. Projected snowfall totals drop significantly as you go west, with mid-Island and Central Connecticut forecast to see 4-8″, and points west (including NYC) receiving 2-4″. Wind will also be a factor with a tightening pressure gradient caused by the rapid intensification of the coastal low.

Timing

Light snow is already falling over the area now, but the worst of this storm should take place in the evening and overnight hours. Snow and wind should pick up in intensity from southeast to northwest throughout the day. If you have made plans to travel along the NYC-Providence-Boston corridor, expect travel conditions to become hazardous this evening/night. The most intense part of this storm will be ongoing from about 6PM-1AM, but accumulating snow will begin around 3PM.

Notes

As with most storms this winter, there is still uncertainty as to the final track of the storm. Should the storm track slightly westward, and the deformation axis determining where a heavy band of snow progresses further inland, then areas west of where current winter storm warnings exist could see significantly higher snow accumulation. There is also some indication that a norlun trough might form, leading to a intense snow band projecting west/northwest from the center the coastal low. If this feature does develop, areas that this trough sits over could see much higher than projected snowfall.

Satellite image of the incoming storm below:

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NYC Weekend Weather – Feb 14, 2014

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Check out this impressive satellite image of the nor’easter that hit us yesterday. It’s now offshore of southeast Maine, and has strengthened considerably, taking on a classic “comma head” structure that is a hallmark of strong surface low storm systems.

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Don’t shoot the messenger, but we are forecast to get even more snow Saturday. A clipper system to our northwest over Michigan will combine with another low pressure system moving into the Carolinas later today. Once this system moves offshore, it will begin strengthening and growing into another nor’easter. Luckily, forecast models are currently showing much lower amounts of available moisture (precipitable water) for this upcoming storm. In addition, even though the storm is forecast to pass near us, the bulk of the precipitation is currently forecast to remain over the open ocean. What this means is that we should only see light accumulations of snow, on the order of 1-3″. However, as with the previous storm, there is still a little uncertainty about the final track of this storm, and changes could lead to higher snowfall amounts.

Otherwise, expect milder temps today with windy and sunny conditions prevailing, temps in the low 40s. This should help some of the snow to melt. We should have clear skies for part of the evening to see the full moon on Valentine’s Day. Clouds move in overnight, with snow showers during the day Saturday and a high in the mid 30s. Another weaker clipper system moves in Sunday with another chance for light snow and high temps around freezing. Yet another system is forecast for Monday night into Tuesday, which looks to be snow to start and snow transitioning to rain on Tuesday. Monday’s high near freezing with a warm up Tuesday ahead of the frontal system moving in.

Here’s a graphic showing the snowfall totals from around the area from this last storm.

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Nor’easter Update – 7PM Feb 13, 2014

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We’ve enjoyed a period of relative calm as the dry slot (orange outlined in purple below) mentioned earlier pushed in over the area, leading to a lull in heavy precipitation and more of misty drizzle. However, these conditions will not last as the nor’easter will gain strength overnight.

The mid-upper level low that is responsible for bringing in this dry slot will gradually move over the surface low pressure center currently located offshore of central NJ. Once the low pressure systems stack up, the surface low will rapidly deepen. As this occurs, the warm front extending from the nor’easter’s core will rotate to the NW of the storm center.

This frontal boundary will push moist air (greens and yellows in this image below) ahead of it, leading to the formation of a new heavy band of snow – technically a “frontogenetically induced deformation band”. Within this band, snowfall rates may hit 1-2″ per hour, and an additional 4-8″ could accumulate across the region (except eastern Long Island). Interior areas where temps have remained cold could see an additional 8-12″ overnight.
Screen shot 2014-02-13 at 7.03You can already see in the radar image below that precipitation is already filling back in across southern NJ and the WAS-BAL-PHL corridor.

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Nor’easter Update – 12PM, Feb 13, 2014

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Satellite water vapor imagery clearly shows an area of drier air (in orange), known as a dry slot, working its way into the nor’easter currently impacting the NYC area. Intense bands of snow continue to push into the interior areas north and west of the city.

However, radar imagery from Mount Holly, NJ NWS office is already beginning to show a break in precipitation associated with this drier air. As this dry air works its way north, we can expect a break with lighter snow/rain for the area. This could work to lower overall snowfall totals in areas that see this break. At the surface, snow has transitioned to rain/sleet for most areas in NYC, Long Island, coastal NJ and southeastern CT. The rain/snow line should remain stable in its current position for the remainder of the afternoon.

Precipitation should transition back to all snow during the evening and overnight. Additional accumulation is expected with more large-scale banding features forecast to form on the backside of the nor’easter low pressure center as it intensifies and exits to the northeast. Another 3-5″ is possible overnight in the city. Snowfall totals in areas north and west should easily top 12″ by the end of this event.

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NYC Noreaster Update – 6PM Feb 12, 2014

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Everything is on track for this strong noreaster to begin moving into our area late tonight. NWS forecast office in Upton has upgraded all areas in the NYC metro to winter storm warnings ahead of the storm. The low pressure center responsible for this weather will move offshore of the Delmarva Peninsula and begin a process of rapid strengthening as its central pressure drops precipitously by 25mb.

Snow will begin falling over the area from south to north after midnight tonight. Heavy snowfall rates of 1-2″/hour are possible with a large scale snow band  forecast to develop due to the influence of a strengthening frontal boundary. By morning, NYC will pick up at least 3″ of heavy, wet snow, making for a messy commute. Snow will continue falling during the morning commute, heavily at times, limiting visibility. Snow transitions into sleet and possibly some rain around the coastal areas during midday. If rain mixes in, areas near the coast would see minimal additional snow accumulation during the day. If rain does not mix in, then another 6″ is possible.

Areas in the interior will see snow start later than NYC and the coast, but will continue to experience all snow or a sleet/snow mix during the day Thursday. These areas will pick up an additional 6″+ during the day Thursday, with another shot at picking up 6″ or more Thursday night as bands of snow continue to rotate around the center of the low.

As the storm departs to the east, it will continue to strengthen. The tightening pressure gradient will lead to stronger winds, with gusts as high as 40-50mph in some parts, leading to blowing and drifting snow. The heavy, wet snow associated with this storm has the potential to knock out power and collapse roofs already encumbered with accumulation from previous storms.

 

Nor’easter Update – Feb 12, 2014

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High impact nor’easter for the NYC metro area starting tonight. A low pressure system has formed southeast of New Orleans and will be tracking along the Carolina coast before moving offshore of NJ. Once over open water, the storm will begin rapidly strengthening (bombogenesis). Recent model runs have come in with a colder scenario, so less mixing in of rain is anticipated near the coast.

Timing

Moderate to heavy snow will overspread the NYC area in the overnight hours tonight. Accumulating snow will impact the morning commute, before a changeover to sleet near the coast and rain over portions of eastern Long Island. Interior regions will continue to see all snow. Precipitation will continue through the day Thursday, transitioning back to all snow for coastal areas overnight before dissipating early Friday morning.

Impact

Periods of snow, heavy at times overnight Wednesday into Thursday. A large-scale snow band(s) is forecast to form over portions of the NYC area, generally west of I-95 across the interior north and west. Areas under this banding feature will easily see snowfall totals over 12″, with snowfall rates up to 1-2″ per hour. Closer to the coast, snowfall totals generally forecast between 6-10″ of snow and sleet. By morning, we can expect around 2-4″ in the city making for a messy commute. Higher amounts north and west. Additional snow/sleet accumulation in the city of 2-4″ during the day, and ending off with 2-4″ overnight Thursday. Some power outages are possible with heavier snowfall on top of ice from previous storms.

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NYC Storm Update – Feb 11, 2014

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There is increasing confidence that NYC will be seeing a high-impact snow storm Wednesday night into Thursday night. However, there are still discrepancies between different forecast models that are leading forecasters to not place too much confidence in overall snowfall totals. There are two main scenarios that could unfold: 1) the storm center takes a track closer to the coast, or 2) the storm center tracks further offshore.

In the first scenario, warmer air would be able to enter into coastal areas and lead to more rain, thus cutting down snowfall totals in NYC, Long Island, and coastal NJ, CT. In the second scenario, warmer air does not flow in as much. This would lead to higher snowfall totals for all areas of the NYC metro. With snow:water ratios about 8:1, and as much as .75-1.5″ inches of precipitable water available (moisture that can fall as snow, rain, ice, etc.), any small change in forecast track and temperature could lead to significant changes in the forecast total snowfall.

Current forecast:

Timing: accumulating snow will begin falling over the area, spreading from south to north, beginning Wednesday night. During the overnight hours into early Thursday morning, widespread totals of 4-6″ are possible. If the track producing a warmer temps verifies, then snow will mix in with rain along coastal areas during the day Thursday, while remaining all snow inland. A return to all snow will occur Thursday night as temps drop below freezing and the storm system exits to the northeast.

Impact: NWS is forecasting 6-8″ total snowfall for areas along the coast including NYC, with 8-10″+ in areas immediately north and west of the city. This is a total for Wednesday night into Thursday night. Thursday morning commute will be messy, with accumulating snow transitioning to rain making for a slushy mess in coastal areas, and all snow in the interior.

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NYC Snowstorm Update – Feb 11, 2014

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UntitledSignificant winter storm is already underway for large parts of the southeast. Snow, and ice accumulation up to 5″+ in some areas before this storm moves in on the northeast.

Still a decent amount of uncertainty as to final track of this storm. If the storm takes a track closer to land, there will be more rain and less snow. If the center of the storm passes south of NYC near what is referred to as the 40°N 70°W benchmark, this will become an all snow or mostly snow event area wide.

With snow to liquid ratios between 10 and 15:1, even a slight deviation could mean dramatically different outcomes. The city has been consistently forecast to be on the cusp of the rain/snow line so final track adjustments are worth keeping an eye. Current NWS forecast thinking is for accumulating snow to begin falling overnight Wed through late Thurs morning. A changeover to rain is currently expected in NYC and coastal areas which would keep overall snowfall totals down. A change back to all snow would occur as temps drop later Thurs as bands of precip wrap around the center of the low departing east.

Temps today will remain chilly in the upper 20s, with sunny conditions. Overnight lows in the teens, and a similar day weather-wise Wed. Overnight lows Wed in the mid 20s, and hi temps Thurs (critically) just above freezing in this forecast. Warmer on Fri w temps nearing 40.

Details:
All reliable models point to a rapidly deepening low pressure center, with central pressure dropping from 992mb to 970mb in this Navy model forecast as the low moves from our area into New England. A mesoscale banding feature also develops, but final placement is uncertain. Right now, hpc is forecasting axis of heaviest snow from NE PA, northeast through NE NJ, western MA and into down east ME. 6-12″ could easily accumulate under this banding feature.

Details:

All reliable models point to a rapidly deepening low pressure center, with central pressure dropping from 992mb to 970mb in this Navy model forecast as the low moves from our area into New England. A mesoscale banding feature also develops, but final placement is uncertain. Right now, hpc is forecasting axis of heaviest snow from NE PA, northeast through NE NJ, western MA and into down east ME. 6-12″ could easily accumulate under this banding feature.

Storm Update NYC – Feb 10, 2014

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NYC weather update (noreaster?): Still considerable variation between different forecast models in the resolution of the storm track for this upcoming coastal low. Model spread of about 100 mi during the critical forecast period. This could mean the difference between a large snowfall for all areas of NYC metro, or a rain/snow/sleet mix for the city & coastal areas, and all snow inland.

With this much uncertainty in the mix, it’s still hard to say with any confidence how much snow will accumulate. Operational forecasts from the NWS are mixing in rain at the moment during the day Thurs. More updates to come.

Temps tomorrow & Wed remain chill, below freezing in the upper 20s, with lows in the teens again in NYC and single digits further inland. Clear and sunny conditions for the most part until the storm rolls in.

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