FORT CAMPBELL, Ky. (AP) _ Several dozen Army chaplains and an around-the-clock support team offered comfort Friday to families of the 248 Fort Campbell soldiers who died in the crash of a military charter in Newfoundland.

A family assistance center, hastily organized immediately after news of the crash Thursday, was composed mostly of wives and friends of base personnel who volunteered to answer questions by phone or visit homes.

''There continues to be a very somber mood on the base,'' deputy public affairs officer William D. Harralson said. ''There is so much more closeness here than you would experience in any other type of environment.''

Large posters were placed about the assistance center with names of the 101st Airborne Division soldiers who were aboard the chartered DC-8 that crashed. Workers checked off names when they knew families had been notified that their loved were supposed to be on the plane.

The troops were returning home on regular rotation from the Middle East, when the plane crashed just after take-off at Gander International Airport in Newfoundland.

The White House announced Friday afternoon that President Reagan and his wife, Nancy, would fly to Kentucky on Monday morning to attend a memorial service at Fort Campbell.

''It is very appropriate for the president to choose to express the grief and sympathy of the entire nation through such a ceremony,'' Sen. Wendell Ford said in a statement issued by his office in Washington.

At the Pentagon, Maj. Robert Schneider said other members of the peacekeeping force returning to the U.S. would travel in military transport planes, rather than on commercial charters.

''The main concern there was just the peace of mind of those individuals and the families,'' he said, adding that the decision was not prompted by safety considerations.

At the fort, most work went about as usual. Troops continued basic training, soldiers broke for lunch at a crowded fast-food restaurant on the base, and Christmas decorations stayed lit.

But there were signs of mourning, too: A large sign announcing that ''Today's parties have been canceled'' hung outside the Eagle Rendezvous Club for non-commissioned officers.

''My wife is the personnel officer for the dental committee and they were to have their Christmas party this afternoon, but they canceled it too,'' Harralson said. ''It's just not an atmosphere with this tragedy to go out and celebrate.''

Flags waved at half staff in a persistent icy rain.

Media buses were escorted through the base to watch 120 soldiers board a chartered Ryan International 727 jet for a flight to Dover Air Force base in Delaware, where they will serve as an honor guard for their fallen colleagues.

And soldiers admitted that sorrow overshadowed the day-to-day routine.

''That's all that people are talking about right now,'' Capt. Jim Runyan said as he watched a group of soldiers do push-ups in a cold mist.

''There's either somebody you knew or somebody's neighbor across the street,'' he said. ''I knew probably 10 of those men, and some were close friends.

''Everyone's human - when your friend dies, that affects you like everybody else,'' Runyan said. ''This time of year people are more conscious about helping other people, so it extends them that help.''

The volunteers at the assistance center won't answer questions about funeral arrangements until the bodies have been positively identified, Harralson said.

''Right now the No. 1 thing they are trying to do is comfort the families with an individual known to be on the aircraft,'' he said. ''We'll help the families adjust to death and go from that point.''

A ''survival assistance officer'' eventually will be assigned to each family to help with funeral and moving arrangments, Harralson said.

Survivors generally have about 90 days to move off-base, said Maj. Jim Gleisberg, an Army spokesman. That limit can be extended under certain conditions, he said.

For the moment, ''wives clubs are taking care of children and cooking meals,'' Harralson said. ''They are offering other types of assistance that you would find in this type of situation.''

Army families are probably better prepared to handle death than most other civilians, Harralson said. But ''when you have 248 people die at once, that's almost inconceivable in our minds.''

''These people know the constant commitment and sacrifices that their husbands and wives make, but you can never prepare yourself completely for a tragedy of this magnitude,'' he said.