Jan 18, 2012: Tracking Two Snow Potentials

With the cold front moving through the area last night, widespread gusty winds were observed late last night into this morning; immediately after the front passed through last night, wind gusts were in the 35-45 mph range across the area, with windy conditions lasting through the afternoon, gusting up to 30-40 mph across the area as expected. The actual high temperatures today were in the early morning, just before the front passed through, reaching the upper 40s to lower 50s across the area, although temperatures during the afternoon hours were steady in the mid 30s inland, upper 30s to lower 40s in the immediate NYC area, and lower 40s in most of Long Island/S CT. Temperatures are currently dropping across the area, and will reach the lower to mid 10s inland and mid to upper 10s for the north/west suburbs of NYC, Long Island and southern CT by tomorrow morning.

Although the pattern has not changed towards a cold and snowy one, and will not do so any time soon, if it even does so this winter, a set up supporting a favorable storm track with enough cold air will result in two snow potentials for the area over the next several days. Tomorrow night, widespread light snow will fall across the area, with up to 2 inches possible in parts of Connecticut. Saturday, however, will bring a larger storm, bringing a more widespread mix of snow, sleet, rain and possibly freezing rain across the area.

Thursday – Thursday Night: Light Snow Expected

Mostly sunny skies are expected for Thursday morning with high temperatures reaching the lower to mid 30s inland and the mid 30s across the rest of the area. Cloud cover will increase, however, as a weak storm approaches the region from the west. Today’s models are starting to emerge on a better consensus, one that involves less precipitation than the wetter models showed. My scenario map yesterday went along with a scenario in between these wet scenarios which no longer appear to be likely, and the dry scenarios showing no snow in NYC which are still supported by a few models. With the latest model trends, I am keeping my outlook the same with only minor revisions to the snow outlook.

My scenario map for the storm can be found with yesterday’s update, and above, I posted my expected snow map for the area. Accumulations are expected to reach up to 1 inch in the northwestern parts of the area, but with the storm redeveloping too far east, the immediate NYC area will see the least amount of snow, with a dusting to 1/2 inch, possibly up to 1 inch north and east of NYC. Most of the snow is expected to fall in Connecticut, with widespread 1-2 inches of snow, potentially passing 2 inches in the north/eastern parts of the state. Long Island’s forecast is more uncertain; some of the models keep Long Island with snow, while other models show plain rain. Surface temperatures are a bit mild during the event due to onshore winds, and while I do not expect a plain rain event, rain is likely to mix with the snow in parts of Long Island, especially closer to the coast, which should limit accumulations to at least up to 1 inch. A final outlook for the clipper will be posted with tomorrow night’s update.

Friday – Saturday: Becoming Stormy Again, Wintry Mix Expected

Cloud cover will briefly clear for Friday with high temperatures reaching the lower to mid 30s inland and the mid 30s across the rest of the area. The dry conditions will not last for long, however, as yet another storm will quickly move through the Great Lakes towards the region, with cloud cover once again increasing by Friday night. With this storm, there is a stronger cold air mass ahead of the storm, and with the models showing some cold air initially, most of the area is expected to start out with light snow. As the low pressure approaches the area, however, temperatures aloft at 850mb are expected to quickly warm up, already ending up above freezing across the area by 12-1 PM. There is still colder air down to the surface, however, with temperatures still stuck in the 30s across most of the area. Some models, especially the NAM, have been suggesting the potential for sleet and/or freezing rain to fall in the interior parts of the area, and this potential will be closely monitored.

The models are showing different outcomes for the storm, with today’s NAM runs going with a north and warm storm, with mostly rain for the entire area; the GFS has light snow changing over to rain for most places, the ECM has light snow with up to 1-possibly 2 inches changing over to rain near coastal areas and a mix further north, and the CMC also has a light-moderate snow to rain scneario. The models are apparently getting closer to a consensus, however, with the ECM trending warmer from yesterday’s and last night’s runs, both of which suggested a moderate snowstorm for most places north of NYC with yesterday’s run including NYC in that potential, the GFS fluctuating between slightly colder and warmer scenarios, and the NAM trending south from what started out as a rain storm this morning to what is on its latest evening run modeled to be a snow to ice storm for the northern parts of the area.

With the latest trends kept in mind, the latest 5-Day Forecast was changed to show slightly colder temperatures, especially north/west of NYC, with the mention of sleet/freezing rain inland. The latest expectation is for light snow to fall around Saturday morning, and as the precipitation intensifies, the snow begins to mix with rain across the area, with NYC and places south/east changing to rain by noon. Up until that point, light snow accumulations are possible north and west of NYC; although the exact accumulation is still uncertain, from the latest models, at least 1 inch may be possible, if not more towards NW NJ/SE NY. After 12 PM, the interior parts of the area may mix with sleet and/or freezing rain, although the dominant precipitation type elsewhere will remain as rain. The storm will the end by the early overnight hours.

This scenario is not final yet; the models have not settled on a single solution, and it is possible that tomorrow’s outlook may change. A slightly warmer outcome than the above may be possible, although it is just as possible that a colder scenario may be shown with the next outlook, including more snow and less rain. Stay tuned for more information on this storm and its impact across the area.

Tomorrow’s update will also discuss the outlook beyond Saturday’s storm in more details, including the warmer temperatures returning for Monday.

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