Sunday, January 20, 2013

Jan 20, 2013: Snow Returns Monday, Friday


Forecast Highlights:

Today marked the end of the mild pattern, which did not go down uneventfully with temperatures well above average again, peaking in the upper 40s to mid 50s across the area. With a cold front moving through the area, a much colder air mass will remain in place through the week and next weekend, which will be accompanied by two snowstorms, one on Monday night and a bigger snowstorm on Friday.





Tonight - Thursday: Much colder, Some Snow

With the cold front currently offshore, a much colder air mass is making its move into the region, with the coldest temperatures since January 2011 expected for the region. The warmest temperatures of the week, which are still several degrees below average, will be on Monday, peaking in the upper 20s to low 30s across the area, approaching 35 degrees near NYC.

A weak low pressure will affect the region on Monday into Monday night, with scattered snow showers spreading into the region during the day. By Monday night, a stronger low pressure will begin to develop offshore; most of the snow from this storm will be limited to eastern New England and offshore, although at least 1 to 2 inches of snow are likely for Long Island and southern Connecticut, with locally higher amounts above 2 inches possible especially further east. From NYC and further west, totals are expected to remain near or below 1 inch. Breezy conditions are likely as well, with wind chills in the single digits. Some updates will be posted on this storm on Monday night.

Tuesday through Thursday will bring the coldest temperatures in 2 years to the area; while this cold is nowhere near historic intensity, it is still notable for being significantly colder than average. 850mb temperatures are expected to remain near or slightly below -20 degrees Celsius, with partly to mostly cloudy skies keeping high temperatures in the low to mid 20s across the area; interior northern areas may struggle to reach 20 degrees on Wednesday. The same cloud cover, however, will also limit how cold overnight lows end up. At this time, lows are expected to drop into the 10s across the area, with interior NW areas dropping into the single digits on Tuesday night, and a larger coverage of sub-10 degree lows closer to the northwestern suburbs of NYC and coastal CT expected on Wednesday. Depending on cloud cover, interior areas and colder parts of eastern Long Island may approach zero degrees. Wind chills are likely to be in the single digits across the area and below zero inland.


Friday - Saturday: Snowstorm Expected

With the strong cold air mass lifting out of the region, the next storm will move into the region in the late week. The model guidance remains inconsistent with the specific details of the storm, ranging from a suppressed snowstorm with the heaviest totals south of the area, to a further north storm with snow changing to ice and rain. Regardless of these inconsistencies, the overall expectation is for a snowstorm to affect the region, including the area, with at least moderate accumulating snowfall. With the strong cold air mass initially in place, the storm is expected to start out with snow. Should the storm track further north than currently expected, some areas may see mixing with rain and/or ice, although at this time a plain snowstorm solution is more likely. There is not enough confidence level in the forecast at this time to determine accumulations given this is still 5 days away, as this also depends on the track and intensity of the storm, although the overall potential is there for at least a 4+ inch snowstorm to affect the area. Stay tuned for more information on this storm.

Beyond the storm, another cold air mass will drop into the region; while 850mb temperatures will not be as cold as the mid-week time frame, surface temperatures are expected to be cold again for at least a day or two after the storm with more widespread snow cover across the region. Behind the colder temperatures, more indications are showing up for a moderation in the pattern with warmer temperatures returning into the region.

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