After months of having to budget around the most expensive gas in the lower 48 states, Oregon and Washington drivers are about to see pump prices take a nosedive, according to economic forecasters.

In fact, on Friday, Tom Kloza, an analyst with the price-tracking site , sent out this tweet:

Pump prices for #gasoline and #diesel about to plummet in the Pacific Northwest. Wholesale gasoline down 80cts gal since last day of spring. — Tom Kloza (@TomKloza) September 19, 2014

Gusbuddy predicts gas will slide to $3 a gallon in 30 states over the next couple of months.

However, Oregon and Washington, which currently have the nation's third and fourth most expensive regular unleaded gasoline at $3.84 and $3.83, respectively, the average price will likely bottom out at about $3.15 and $3.25 a gallon, Kloza said.

"Fall is appropriately named for fuel prices," Kloza said in an interview with The Oregonian.

Yes, gas prices typically drop in October as the summer driving season winds down and demanded decreases. But in Oregon, it can be hard to predict how much the pain at the pump will ease.

Gas prices

Oregon doesn't have its own refineries. As a result, the state is dependent on an archipelago of oil refineries in Washington and California, where strict air-quality rules require more expensive summer blends. Meanwhile, problems at a single facility can cause prices to spike up and down the coast.

One thing has remained constant in recent months: The Pacific states have the nation's most expensive gas, largely because the region is geographically isolated from refineries that have access to cheaper crude oil in other parts of the country.

Of course, there's also a chance that some discount retail outlets such as Arco and Costco will try to lure customers with $3 gas. That happened in a few locations in the Portland metro area last fall, when some stations dropped prices below $3 a gallon.

MAP: Gas prices across the Portland area.

"Nationally, prices haven't averaged $3 a gallon since 2010, when we were coming out of the recession and there was still $2.50 gas," Kloza said.

Here's are five reasons that gas prices are about to plunge in the Northwest:

1. Domestic oil surge. Crude oil production, driven largely by a North Dakota boom, hasn't hit the current level since March 1986, Kloza said. However, only a trickle of that cheap North Dakota crude is making its way to Oregon and Washington. As a result, he said, the Northwest's gas prices will still remain a bit higher than the other parts of the country. Currently, the refineries producing gas and diesel for Oregon get most of their crude from Alaska's North Slope, Canada, Saudi Arabia, Iraq and Ecuador.

2. A switch to winter blend.

On the West Coast, California refineries find themselves churning out two blends of gasoline — one to meet their home state's stricter clean-air standards and one to sell in the Northwest. Refineries will switch to the cheaper winter blends of gasoline next month.

3. U.S. refineries are humming like they haven't hummed in nearly a decade, according to the U.S. Energy Information Administration. Gasoline production, including at refineries in California and Washington, is at its highest level since the summer of 2005. Steady production without disruptions from hurricanes and mechanical issues means less volatility in the market.

4. Foreign crude prices have plunged more than $15 per barrel since June, when they peaked as the Islamic State militant group captured large swaths of oil-rich Iraq.

5. Improving gas mileage on passenger vehicles and a decline in driving have resulted in decreased demand among commuters, even as the economy picks up steam.

-- Joseph Rose