Forecasters at the National Weather Service on Saturday night slightly lowered their outlook for snow accumulations in Maine from the latest winter storm, but warned that the weather system remained potent and would almost certainly create blizzard conditions Sunday.

John Cannon, a meteorologist at the weather service office in Gary, said forecasters think about a foot of snow will fall around Portland and the rest of southern Maine, down from about 20 inches called for in forecasts from a day or two ago. However, Cannon said some computer models show significant bands of heavy snow that could roll through the Portland area, so he wouldn’t be surprised to see some locally higher amounts.

And midcoast and Down East Maine will see higher amounts of snow, up to about 20 inches by the time the storm moves on Sunday afternoon.

Other than the snowfall totals, the rest of the forecast remains the same, with strong winds expected to blow most of the day Sunday, leading to a lot of blowing and drifting snow. And Cannon said the weather service expects blizzard conditions, which occur when the visibility drops to a quarter-mile or less, there’s heavy or blowing snow and winds are 35 mph or higher.

Mike Cempa, another meteorologist at the weather service office in Gray, said the latest computer models suggest the storm may move slightly farther east than earlier forecasts had indicated and it also may speed up more quickly than expected. But the storm is still expected to lash the state, particularly along the coast, with heavy snow and strong gusts of up to 50 mph Sunday.

The snow will end by about midday along the southwest coast and by early evening Down East, Cempa said, but the winds won’t die down until Sunday night.

Sunday will be cold, with highs in the teens in southern Maine. Cempa said wind chills will be about 5 below zero along the coast to minus 15 to minus 25 inland and in the mountains.

Lows will fall below zero statewide Sunday, he said, and temperatures may only reach 10 above on Monday. Tuesday will be a bit warmer, he said, with highs in the 20s. There’s a chance of snow on Wednesday, but Cempa said at this point, it doesn’t look like a significant storm.

Other forecasters are downgrading their predictions for snowfall more than the weather service. For instance, the Portland Press Herald’s weather blogger and meteorologist, David Epstein, has lowered his snow accumulation forecast to 5 to 9 inches along the southern coast and Down East, and to 1 to 3 inches in the western mountains.

The speed limits on the Maine Turnpike, Intertstate 95 and Intertstate 295 were all reduced to 45 mph early Saturday evening and state transportation officials urged drivers to stay off the roads Sunday.

Mass transit in southern Maine will be curtailed because of the snowstorm.

METRO, the Portland regional bus service, said it will not operate Sunday. The same is true for ZOOM, which serves Biddeford, Saco and Old Orchard Beach and also has routes to Portland. The Amtrak Downeaster, which had planned to run a limited schedule of trains between Brunswick and Boston on Sunday, announced late Saturday afternoon that it has canceled all of its trains Sunday

Parking bans have been posted in communities across the state, including Portland, where a ban was to be in effect from 10 p.m. Saturday until 6 a.m. Monday. There will be parking bans in Falmouth from 6 p.m. Saturday to 6 a.m. Monday and in Scarborough from 6 p.m. Saturday until 6 p.m. Monday.

State officials reported one serious crash Saturday morning at mile 36 of the Maine Turnpike.

Stephen McCausland, spokesman for the Maine State Police, said a van overturned on the turnpike and while state troopers were investigating, two other vehicles collided nearby.

All three vehicles were demolished, McCausland said, but no one was injured.