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Bolaris: Snow to be heavy, steady for hours

Westward facing trees shows signs of the strength of the snow storm in a wooded area near the Cheltenham Mall on Dec. 10, 2013. (RON TARVER / Staff Photographer )
Westward facing trees shows signs of the strength of the snow storm in a wooded area near the Cheltenham Mall on Dec. 10, 2013. (RON TARVER / Staff Photographer )

9:15 p.m. update

The storm is now developing rapidly along the Virginia coast.

Timing is still on target with most snow accumulations taking place here by 4 a.m. Friday. Winds will increase quickly now and snow banding will and has been taking place. Dangerous wind chills of sub-zero will set in overnight and through Friday morning as temperatures drop through the teens and into the single digits.

There will be plenty of blowing and drifting of snow through early Friday afternoon. Travel will become extremely hazardous overnight and Friday morning.

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  • Will post snow totals by 7 a.m. with 4-8 inches expected throughout the immediate Philadelphia area (6 inches being the average amount). Yes, some places will hit the high end of range and isolated excess amounts.

    The bullseye of heaviest snow should be north Ocean and Monmouth counties in New Jersey, where 8-12 inches is possible.

    Eagles gameday forecast: Dry and cold, with kickoff temperature around 25. Wind will be a non-factor.

    John Bolaris

     

    Earlier forecast and discussion

    Finally, computer models are coming together on a developing snowstorm for the northern Mid-Atlantic and all of the Northeast, with a full-blown blizzard across Long Island, the Capes, Boston and most of Coastal New England.

    Still debating whether a blizzard warning will be issued for sections of the New Jersey shore from northern Ocean County through Monmouth.

    (A blizzard warning is defined as "sustained wind or frequent gusts greater than or equal to 35 mph, accompanied by falling and or blowing snow, frequently reduced visibility to less than 1/4 mile for three hours or more.)

    Keep in mind, even though a blizzard warning has not been issued as of noon today, it's very likely that most of us will feel localized blizzard conditions starting late tonight, mainly after 10-11 p.m. and for sure during the overnight.

    The set-up

    A secondary coastal storm will form this evening off the Virginia coast and then rapidly intensify as it quickly moves northeast to a position off the New England coast by noon Friday.

    The very latest computer models are generating slightly more QPF (quantitative precipitation forecast), which equates to slightly higher snow amounts.

    Also, what is becoming interesting to me, is that even the coastal sections should get into the heavy snow, as the atmosphere will crash (experience rapidly cooling columns of air). Computer models have a hard time keeping up with this, so I believe the heavy snow line will expand all the way to the shore lines.

    That means widespread heavier snow seems likely now for the entire region.

    Timing

    The snow starts to overspread the region between 5 and 7 p.m., with some mixing with rain at the start mainly across southern New Jersey, and central and southern Delaware.

    Brunt of the storm: From 10 p.m.-4 a.m. Temperatures plunge into the teens overnight, winds rapidly increase, gusting at 35+ mph.

    Bands of moderate to heavy snow likely, with rapid accumulations. Roads will quickly become snow-covered and extremely hazardous. Blowing and drifting of snow, with visibilities dropping to less than a 1/4 of a mile producing localized blizzard conditions at times.

    Wind chills will be dangerously cold, dropping to sub-zero.

    STAY INDOORS!

    Friday morning: Leftover snow showers , especially across coastal sections. Blowing and drifting of snow, reduced visibilities, temperatures of  8-15 degrees with wind chills of 10-20 below zero.

    Friday afternoon: The sun returns. Windy and bitter cold, with highs in the teens.

    Latest snow amount estimates

    Generally 4-8 inches across most of the region, with Philly included.

    North Ocean and Monmouth counties should receive the highest amounts, with 6-10 inches.

    Poconos: 8-10 inches.

    Cape May County and southern Delaware: 4-6 inches.

    Central and northern Delaware: 4-8 inches.

    My thinking is just about everyone in our region should hit the base number of 4 inches. Additional amounts will depend on potential heavier snow banding and 15-1 ratio of liquid to snow. (Meaning one inch is equated to 15 inches of snow.)

    NYC: 5-9 inches.

    Long Island: 6-12 inches. Blizzard warning.

    Boston: 12+ inches.

    Washington, D.C.: 3-5 inches.

    It's going to be real-time forecasting as the storm develops tonight, so join me tonight starting at 6 p.m. here on philly.com to answer your questions and adjust the forecast in real time.

    John Bolaris


    John Bolaris For Philly.com
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