Monday, November 24, 2014
Inquirer Daily News

Bolaris: Big, late winter snow - or not?

NOAA´s 6-10 day precipitation outlook predicts a 50-60 percent probability for above-normal precipitation. (NOAA)
NOAA's 6-10 day precipitation outlook predicts a 50-60 percent probability for above-normal precipitation. (NOAA)

What a long, long winter it has been - 67.4 inches of snow making it the second snowiest winter of all-time. Persistent cold and wind, potholes spreading quicker than diaper rash and any real thoughts of spring get quickly diminished with the next blast of polar air.

Yes we will have a spring tease on Saturday as temperatures ride into the 60s, however, the next blast of unseasonably cold air will start to arrive on Sunday as temperatures cool back into the low-mid 40s.

All computer models have been indicating strongly that a storm system will begin to take shape along the southeast coast on Tuesday and begin to move northeastward. The storm has the potential to become very intense somewhere off the Northeast coast.

The set-up

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  • Energy will dive southeastward from the upper Plains late in the weekend and eventually produce storm development off the Georgia coast early Tuesday. At the same time an arctic high - very strong for this late in the season - will be centered over northern New England, supplying unseasonably cold temperatures across all of the Northeast and Mid-Atlantic region.

    The cold Northern jet stream will phase with the moist and stormy Southern jet stream as the energized trough (deep atmospheric valley which enhances storm development) in the east will begin to pivot negative. (A negative tilt helps to intensify and in some cases will actually pull the storm on a more westward movement toward the coastline.)

    Now all of this will eventually lead to a very intense cyclone in the western Atlantic with the big question being where exactly does this rapid intensification process takes place.

    Right now it appears that the phasing and the negative tilting of the trough should be delayed just enough for the Philadelphia region to escape a major late winter snowstorm, with southeast New England in the possible crosshairs of a full blown blizzard with winds gusting to hurricane force and blinding snow.

    But if phasing and tilting of the trough should occur sooner than later in the forecast period, the crosshairs would shift more south and west into the Delaware Valley.

    This storm has quite of few similarities to the March 2nd storm of 1960, when the capes of New England picked up 31 inches of snow as Philly in comparison picked up 7.9 inches and NYC more than 14 inches. This is not a prediction of how much snow will fall with this storm, but rather compatible atmospheric set-up.

    A good chunk of my long-range winter forecast was based on the winter of 1960-61. 

    The bottom line

    Philadelphia is going to get snow starting later in the day on Tuesday with the best chance of accumulating snow again across coastal New Jersey.

    How much snow, the extent of tidal flooding and wind strength is up for meteorological grabs at this time. I should also mention that the main impact of the coastal storm will take place Tuesday night into early Wednesday morning.

    In summary

    We still have a low-level threat for a significant-to-major snowstorm at 30-40 percent for the Delaware valley.

    Will update with any significant changes. Happy Spring!

    John Bolaris

    John Bolaris For Philly.com
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