Maryland had one of the largest job losses in the nation last month, grim news that came Friday as BP Solar announced it is laying off 320 manufacturing workers at a sprawling plant in Frederick.

The U.S. Department of Labor counted 13,800 fewer jobs in the state last month than in January, a decline topped only by Virginia, California, Michigan and Pennsylvania. It was Maryland's largest one-month loss of the recession, which began December 2007.

Economists suspect the February wallop was caused at least in part by the back-to-back snowstorms and could prove temporary. But BP Solar's layoffs are not.

The company said it immediately shuttered its Frederick manufacturing operation, which handled silicon casting, wafering and cell manufacturing. That leaves 110 workers in sales, research and project development, at least while the company decides where those jobs should go long-term.

With February's job numbers, Maryland's unemployment rate rose to 7.7 percent, from 7.5 percent in January. That narrowed the gap with the national rate, which was 9.7 percent both months. The figures are preliminary and adjusted to account for seasonal changes in hiring and layoffs.

BP Solar said the Frederick plant was its last wholly owned manufacturing operation. Like many other employers, it has shifted that work to lower-cost, joint-venture facilities in India and China, as well as to outside manufacturers in Europe and Mexico.

"This is a very difficult day for us, and clearly for the employees that have been affected," said Pete Resler, a BP Solar spokesman, who added that laid-off workers will get three months' pay and benefits with a severance package to follow.

Richard Griffin, director of the Department of Economic Development for the city of Frederick, said the BP Solar plant has been in town for at least two decades. City officials are hopeful the company will keep its research and development work there and eventually expand it.

"We're making the best of obviously not-so-great an event," said Griffin.

The last major announcement of layoffs in Frederick also came from BP Solar, which cut 120 jobs last year when it shut down one of its manufacturing lines. Though city officials were aware the company was looking to cut costs this year, they were not prepared for a shutdown.

Gov. Martin O'Malley, a Democrat, said state agencies will be setting up at the Holiday Inn in Frederick for six days during the next three weeks to help workers apply for unemployment benefits, look for work and sign up for other assistance.

"While Maryland's unemployment rate remains below the national average, today's announcement is a reminder for all of us that families in our state are not immune from the global economic downturn," he said in a statement.

While the unemployment rate has risen, the picture painted by last month's numbers could be worse than reality. A job disappears from the count if the person who holds it isn't paid when the government does its survey, which last month was the pay period that included Feb. 12 - two days after the second snowstorm. Many employees couldn't get to work that week, though not all had their pay docked.

According to the Labor Department, the snow had little effect on the jobs estimate because workers would be counted as long as they were paid for at least a single hour during the week or two weeks that made up their pay period. But several economists, and officials with the Maryland Department of Labor, Licensing and Regulation, said it sure looks like the record-breaking snowstorms decreased the job count.

Two of the other states with the biggest job losses last month - Pennsylvania and Virginia - also were hard-hit by the storms, said Glenn Wingard, an economist at Moody's Economy.com. He doubts that's a coincidence.

Charles W. McMillion, president and chief economist of MBG Information Services in Washington, said another clue is that the losses in Maryland were "pretty broad-based" last month.

"There were just entire parts of the economy that were essentially shut down for a week," said Bernie Kohn, a state labor department spokesman. "It's hard to believe that wouldn't have some impact."

Blizzards aside, McMillion said he thinks the worst is over for the job market.

"I expect that meager job growth will return in the next few months," he said. "Nobody should expect a strong recovery - that just ain't out there. But it does just feel like it's stabilizing, and certainly in this region."

Wingard said temporary hiring at the U.S. Census Bureau's Suitland headquarters will help push Maryland employment in the near term, probably followed by a decline as those 2010 Census jobs end. But he does expect permanent job growth by year's end.

The jobless rate likely will rise rather than fall this year, though, because discouraged workers who gave up earlier will start looking for work again. Wingard doesn't expect the rate to improve to about 4.5 percent - normal for Maryland - until late 2014 at the earliest.

Job losses in construction also have weighed heavily on the state. Employment in the sector is down 27 percent since the middle of 2007, while total job loss in the state during that time is 5 percent.

"Construction has really taken it on the chin," said Champe C. McCulloch, president of the Maryland chapter of the Associated General Contractors of America.

The manufacturing employment base in Maryland also has withered, with 13 percent fewer jobs in February than in the middle of 2007.

State Sen. Alex X. Mooney, a Republican whose district includes the BP Solar plant, called the closure a "huge loss, especially with a struggling economy."

"Those were high-paying jobs, and it's not like those laid-off employees have anywhere to go," he said. "They were supposed to be expanding, and now this."

Del. C. Sue Hecht, a Frederick County Democrat who helped win stimulus money for BP and pushed solar tax credit legislation that would benefit them, said she is "extremely sad and disappointed."

"We were really proud to have them in Frederick, and we have worked really hard to help them stabilize and expand," she said. "To think that we're going to lose all of those jobs, it breaks my heart."