The nationwide coal strike, nearing the end of its eighth week, is starting to pinch.

While coal supplies remain adequate in most sections of the country - although sometimes hard to get at because of bad weather - stores are beginning to run out in the band of states stretching from western Maryland and Pennsylvania to Central and Southern Illinois.

Although blackouts in these states are not a near-term prospect, many utilities already have asked customers to cut back on nonessential usage, and are planning to ask state governments to impose mandatory restrictions if supplies dwindle much further.

Utilities get edgy when their supplies get down below 50 days' worth, noted Alexander Gakner, who has been tracking the coal supply situation for the Department of Energy.

"Even if the strike were ended tomorrow," Gaknersaid, "it would be three to four weeks before coal production was back to normal."

Negotiations broke off last week although they may resume soon. Wages, pension benefits and production stability are reportedly the main issues in the talks.

Coal production has been more than halved by the strike, which began Dec. 6. The situation is worst in the eastern part of the country, where the striking United Mine Workers union is strongest. Even many nonunion mines have been shut down by the strike.

West of the Mississippi there is much more coal production, but little is available to the East because of contracts and difficulty in shipping.

The Alegheny Power System - which owns five utilities serving more than a million customers in Maryland. Virginia, West Virginia, Pennsylvania and Ohio - has less than a 40-day supply of coal.

The utility has already appealed to its customers to trim their electricity usage and has filed a proposed curtailment plan with each of the five states it serves.

If the states approve Allegheny's plan, a spokesman for its subsidiary Potomac Edison Co. in Hagerstown said, unecessary outdoor lighting would be turned off, night operations of retail business would be cut back and public buildings would be closed earlier.

As supplies decline further, the utilities would first cut back on commercial and industrial users, then provide them almost no power, and, in a final move, would rotate blackouts among all its users.

Even these drastic steps, however, would only stretch out fuel supplies, Gakner noted.

Other utilities have taken steps similar to those of Allegheny.

The Appalachian Power Co. in Charleston, W.Va., a subsidiary of the giant American Electric Power System, has less than a 60-day supply left, and already has asked customers to cut off nonessential lights. Duquesne Power and Light in Pittsburgh is in shape similar to Allegheny.

The areas most deeply affected by the strike include western Maryland, western Pennsylvania, Ohio, West Virginia. Virginia, parts of Indiana, Illinois and Kentucky.

In these areas, utilities are more heavily dependent on coal to fire the boilers that generate electricity than are utilities in other parts of the country.

Allegheny Power's generating capacity is 95 percent coal, for example, and most of the nearby utilities are similarly dependent on coal.

The companies are in the heart of UMW country, too, noted one federal official, which prevents them from getting any coal shipments, which trickle to other utilities in the East.

Overall, the nation's supplies of coal should last another 84 days, according to the latest figures from the Department of Energy, covering the period through Jan. 14. Utilities had 110 days strike.

But those figures not only mask regional variations in coal inventories, they also can mask variations within an individual utility, according to Gakner.

For example, he said, Tenessee Valley Authority has an 80- to 85-day supply of coal for its entire system. But nearly half of its stock is at one plant - Paradise. There is enough coal at Paradise to keep its generators operating at full capacity for 145 days.

TVA had been doing just that, to cover for plants like Gallatin, where coal stores were inadequate. But a week ago, a generating unit at Paradise had a serious failure.

TVA decided to move some of the coal it had stored at Paradise to the Gallatin plant, but the night before the railroad cars were to move the coal, the railroad trestle out of Paradise burned down, Gakner said.

So, while TVA may have 85 days' worth of coal, much of it cannot be burned.

In times of spot shortages, utilities can borrow electricity from electric companies with a surplus.

But, Gakner noted, while power can be transferred around to help one or two utilities, there are not enough interconnections to help 10 utilities - even if there were enough power at other U.S. power companies to begin with.

The first customers to lose power in a systemwide curtailment are industrial and commercial. U.S. Steel Chairman Edgar B. Speer said last week that he expects big users like steel companies to begin to face cutbacks by the middle of February.

So far the strike has had few side-effects on the economy, according to Federal Reserve Board industrial production expert Joan Hosley.

About 160,000 miners are not working - including nearly 24,000 nonunion miners - and big coal-hauling railroads like the Norfolk & Western and the Chessie System have laid off workers. Nearly 4,300 of Norfolk & Western's 25,000 employes are laid off because of the coal strike.

But if the strike goes on much longer - it appears Labor and management may get back to the bargaining table soon - power cutbacks will begin. At first it would be a trickle, but by the end of February there could be some noticeable layoffs in states like Pennsylvania and Ohio.

Some governors, like Ohio's James A. Rhodes, have urged the administration to take steps to end the strike.

But administration officials said neither the president nor his advisers have seriously considered invoking the Taft-Hartley injunction to send miners back to work for a 90-day cooling-off period.