Dec 28, 2012: Saturday Snow Forecast

Forecast Highlights:

After an unusually mild December, a winter pattern gradually began to spread through the US starting mid December, and will reach the NYC area starting tomorrow with a snow and rain storm expected for the area tomorrow. Behind this storm, a sustained cold pattern will develop going into the first week of January, with very cold temperatures possible as well as a few snow shower potentials, one of them on New Year’s Day.


Tomorrow’s Storm: Final Forecast

After two marginal snow events for the area this last week, one on the evening before Christmas and another one on Wednesday, with snow changing to rain and wind, another storm will affect the area on Saturday. Last night’s update mentioned that minor changes in the setup are still possible; this continued with today’s model guidance, and each run has trended towards a slightly stronger, wetter and more west coastal low pressure. While this increases the snow amounts for the region, along with the further west storm comes the issue of mixing; with the original further east track, most of the area looked to stay with plain snow, but with this trend, mixing with rain is becoming increasingly likely for the eastern half of the area.

Storm Setup: The storm consists initially of two lows, one tracking into the Ohio Valley through Kentucky and then into western Pennsylvania, with a weaker low pressure close to the coast in the Southeast. Snow will spread into Pennsylvania and New York with the low in the Ohio Valley on Saturday morning; meanwhile, the coastal low pressure will begin to intensify, and will become the dominant low as it moves up the coast. As it does so, precipitation will weaken over the interior, with heavier precipitation spreading into Long Island and southern-central New England, with the higher snow totals from this storm likely in New England. In between these two areas of precipitation in the interior Northeast and the coast, there could be an area of lower precipitation, which at this time looks to set up close to the Interstate 95 corridor southwest of NYC.

Forecast for NYC Area: Precipitation from the Ohio Valley low will spread into the interior Northeast on Saturday morning, reaching the area towards 7-9 AM. With marginal surface and 925mb temperatures, a mix of rain and snow is expected in Long Island, with snow in NYC and north and west. Intensity of the precipitation is expected to be generally moderate. Slightly heavier precipitation is expected towards the late afternoon and evening hours as the coastal low gets closer and intensifies, with precipitation ending from west to east around 6-9 PM. NYC is also expected to have rain at times, although rain is not expected to be the dominant precipitation type at this time, as with western Long Island. Eastern Long Island into coastal New Jersey, however, are likely to see mostly rain.

Forecast Accumulations: At this time, 2 to 4 inches of snow are expected in northern NJ, 3 to 6
inches in SE NY and southern Connecticut, and 1 to 3 inches in NYC and Long Island, locally higher in some areas. As previously mentioned, it is possible that an area of lower precipitation ends up southwest of NYC, with the highest snow totals from this storm expected into Pennsylvania, upstate New York, and into southern and central New England. Given the uncertainty with the exact precipitation amounts concerning the development of the coastal low, as well as the rain/snow line, the current forecast may be subject to minor revisions on Saturday morning once the blog goes into live storm update mode. Should the coastal low pressure develop earlier than modeled with colder temperatures, snow totals would be higher than currently expected, including NYC and Long Island; at the same rate, it is also possible more mixing with rain takes place and totals end up lower than currently expected.

Storm updates will be posted both here and on the twitter page starting on Saturday morning and will occasionally continue throughout the day. A forecast update will be posted on the morning, reviewing the ongoing conditions and whether any revisions need to be made to tonight’s forecast.

Next Week Update: Colder temperatures will return behind this storm, with highs in the upper 20s to low 30s and lows in the upper 10s to mid 20s away from NYC. Mostly cloudy skies are expected for New Year’s Eve with temperatures in the upper 20s to low 30s in NYC, with scattered snow showers expected on New Year’s Day and perhaps into January 2 as well. With a strong trough over the region, any storm is likely to remain suppressed at this time, with much colder temperatures likely towards mid-late next week, with highs likely in the 20s, possibly 10s inland, with lows in the 10s for most of the area and potentially the single digits inland. Temperatures will warm up again by next weekend.

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