Bolaris: Conservative models see heavy snow; 12+ for Chesco?

The extremely complicated storm to come still has computer models with a large degree of uncertainty. So how to answer the big question you all want answered: how much snow is going to fall in my neighborhood? It's the billion dollar question as the North American model is burying us with a foot plus of snow along the I-95 corridor.

I usually don't buy into this model until we are about 24 hours out from the storm. So if the next computer run comes in and stays the course then I start to worry. In the past this model usually has a cold bias and runs quite robust with precipitation amounts.

For now it's my outlier.

Blending the European model (which has been the most consistent), Global and Canadian models, I'm holding steadfast with my forecast.

NOAA (the National Oceanic Atmospheric Administration) is now sending aircraft into the Gulf of Mexico to collect additional weather data so computer models can get a better handle on the developing storm.

The set-up

The storm system will emerge from the Gulf of Mexico on Wednesday night and be in a position along the North Carolina coast by Thursday morning. Energy from both the northern and southern jet should phase along the Mid-Atlantic coast leading to a rapidly intensifying storm. This, in combination with a very strong arctic high centered over northern New England, will feed a cold supply at the same time Atlantic moisture gets pulled into the storm's circulation.

The intensifying storm will move slowly northeast spreading heavy snow, ice and flooding rains all up and down the Eastern seaboard. This is a classic Nor'easter.

Knowing where exactly the snow/rain line sets up is still quite difficult at this time. But I do have it pushing through Philadelphia and into sections of our northern and western burbs.

Timing

10 p.m. Wednesday-midnight Friday: Light snow arrives.

Overnight into Thursday morning commute: A band of some very heavy snow will develop, with the possibility of thundersnow (a thunderstorm with snow) and snow rates could reach 1-2 inches in a few hour span.

This should set up close to the I-95 corridor.

City: Between 8-11 a.m. a changeover to sleet and rain should take place. Before it does, 4-6 inches of snow is likely. Between 11 a.m.-4 p.m. a lull in the precipitation is likely with occasional rain mixed with sleet.

After 5-6 p.m., there's a changeover back to snow with some additional accumulations .

All precipitation moves out between 9 p.m. Thursday and midnight Friday.

Total accumulations for city and I-95 corridor: 6-8 inches.

Highest impact

Chester, Berks and Lancaster counties: a foot or more possible. Mainly all snow.

Upper Bucks and western Montgomery counties: 8-10 inches, with mixing by noon, back to all snow by late afternoon.

Delaware County: 4-7 inches, with mixing by 8-10 a.m.

Lehigh Valley: 6-8 inches with a sharp cut-off of the heaviest snow.

Eastern Montgomery and lower Bucks counties: 7-9 inches with mixing by late morning.

NE Philly: 7-8 inches, with mixing by 9-10 a.m.

New Jersey:

From the Delaware River, east to I-295, 6-8 inches.

All points east of I-295 to the Garden State Parkway, 4-6 inches.

Shore locations: Around 2 inches.

Mercer County: 8-10 inches.

North Burlington County: 6-8 inches.

South Burlington County: 4-6 inches.

North Ocean County: 4-6 inches.

Monmouth County: away from coast, 8-10 inches.

Delaware:

New Castle: 6-8 inches.

Kent: 4-6 inches.

Sussex 2-4 inches.

Tidal flooding will take place during two high tide cycles.

Keep ya posted.

John Bolaris