Feb 27, 2012: Rain NYC, Mix Inland Wednesday

Forecast Highlights:


- Stormy Wednesday: Rain in NYC, Snow/Mix to Rain Inland
- Up to 3 inches are possible in SE NY/southern CT
- Storm followed by another one for Saturday, warmth and rain return
- Drier, colder by end of weekend into early week


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With a weak low pressure staying well to the north of the area, today brought partly sunny skies and warmer temperatures, with highs peaking in the lower to mid 50s in SE NY/NW NJ and the upper 50s to near 60 degrees in NE NJ and most of NYC, although colder temperatures were observed near the coast, where JFK up to Long Island and southern CT had highs in the upper 40s to lower 50s.

The latest radar to the left shows that precipitation associated with the weak storm is starting to move out of the region, with skies expected to clear tonight into tomorrow morning. The next storm will quickly follow, however, with rain returning to NYC by Wednesday. This storm will contain an element that not many storms this season have had: snow, with accumulations in the interior parts of the area and the possibility of some flakes in NYC itself.


Tomorrow's Outlook:


Tuesday will bring mostly sunny skies to the area with colder temperatures, reaching the mid 40s across the area. Parts of the immediate NYC area may reach the upper 40s but staying below 50 degrees.


Wednesday - Thursday: Snow Inland, Rain Near Coast


The previous discussion mentioned how a storm was expected for this time frame, and although it appeared colder, there was still uncertainty. With the energy for the storm moving onshore today, it was better sampled, and the models corrected several features that yesterday's models had which caused them to change their outlook from a colder/snowier one to a warmer outlook. Yesterday's models took the primary low pressure through Michigan with a secondary low pressure forming near the Delmarva Peninsula, which seemed to be a less likely solution given the very large distance between the two areas. With stronger confluence and a stronger high pressure, the storm started out with more snow in NYC and a significant snow event north of NYC. Today's models, however, are already stronger, further north and more amplified with the storm for the short range, and with slightly weaker confluence, the whole storm is further north and warmer than yesterday's models, with a primary low track through northern Michigan and a secondary low forming not too far south of Long Island. Although this supports a warmer solution than yesterday's models, the amount of cold air damming in place as a result of the high pressure in place is still not certain, leading to some uncertainty with the exact rain/snow boundary lines.

With tonight's update, I sided in between the warmer and colder models; the GFS is likely too warm and underestimating the cold air in place. The latest models offer conflicting signals, with the CMC showing plain rain for southern CT and the NYC area, while the NAM, GFS and from early indications the UKMET as well trending colder with at least a 2-4 hour period of snow possible in NYC. Perhaps the 0z NAM may have been overdone with the cold air, but given this year's history of the models failing to settle on a solution even 36 hours away from a storm, it's still uncertain whether the northern or southern scenarios verify. For now, I went in between, but this forecast is not a final one and is subject to slight north/south shifts with tomorrow's update.

At this time, the latest expectation is for precipitation to develop in the late morning hours. With temperatures cold enough, most of the area should start out with a brief period of snow, possibly in the form of a moderate burst of snow near and north/west of NYC. Surface temperatures, however, will limit accumulations, if any, for NYC and its immediate north/west suburbs. Further inland, a longer period of snow is expected, but with the storm aligned in a NW-SE type snow line, interior southern Connecticut is likely at this time to see the most snow in the area, with over 3 inches possible. By the evening, the area should change over to rain except for higher elevations inland, which may see some freezing rain but with no significant ice amounts, and as the secondary low moves offshore, occasional showers will continue through Thursday with highs reaching the lower to upper 40s across the area.

As previously mentioned, this is still a preliminary forecast, and is subject to some changes with tomorrow's final forecast. Uncertainty focuses on the boundary of the rain/snow line and the more significant snow accumulations. It is possible that a north trend is correct and most of the area will see very little snow. However, should a trend to a colder storm start, with some of the 0z model runs coming in colder, the forecast may be adjusted to a colder one with some more snow in NYC prior to the changeover and more accumulations inland. Stay tuned for an update on the storm on Tuesday afternoon.


Longer Range Overview:


The latest models bring in another storm on Saturday, with the latest models bringing a strong storm through the Great Lakes with heavy rain for the area, temperatures getting close to 60 degrees, and even thunderstorms. This scenario, however, seems odd given this pattern, as not a single storm this winter took a track straight through Quebec while bringing in temporary blocking near Greenland in the way that most models depict this storm. In addition, the storm on Thursday night which brought snow to southern Connecticut at one point was also modeled to cross the Great Lakes with warm temperatures and heavy rain, just as Wednesday's storm was before it became apparent it would bring snow to New England. This storm will still bring rain due to the lack of any feature to keep it suppressed, but at this time I am going with a cooler, weaker and not so wet storm on Saturday, although there will still be a storm in the region on that day. Colder and drier conditions will return by the second half of the weekend into the early week. Stay tuned for more details on the longer range outlook.