NEW YORK (PNN) - October 29, 2012 - Gas prices are likely to spike in the days after Hurricane Sandy rips through the northeast, but they should drop back down before too long.

The largest Atlantic storm ever recorded is making its way through the heart of the East Coast's oil refinery region. Sandy's fierce winds and unrelenting rain will be pounding major refineries in Delaware, New Jersey and Pennsylvania. Many have already shut down temporarily.

The region's largest refinery, which is run by Philadelphia Energy Solutions and processes 330,000 barrels of oil a day, is running at reduced rates.

Among those shut down is the region's second largest, Phillips 66's Bayway Refinery in Linden, New Jersey, which processes 238,000 barrels of oil per day. Refineries operated by Hess, NuStar and others have also shut down entirely.

The real impact would come if damage from flying debris or power outages takes some refineries offline for several days. That's because the capacity of northeast oil refineries is much smaller than it used to be; they handle just under 1 million barrels of oil per day.

The northeast is now more reliant upon pipelines from the Gulf Coast and ships traveling through the Atlantic Ocean; and ships can't make their way through the Atlantic yet because the storm is so large.

An extended delay to refinery production in the northeast would start a domino effect that could push the national average price of regular, unleaded gasoline from $3.54 on Monday to $4, according to Rich Sherman, a supply chain expert with Trissential. He said oil tankers are sitting at sea up to 1,200 miles away from the area. Starting up again after the storm will be akin to driving forward in a traffic jam.

However, any spike in prices could be dampened by a pullback in consumer demand, said Tom Kloza, chief analyst at the Oil Price Information Service, which compiles prices for AAA.