In the second attempt this year to tally the county's homeless population, an area homeless services council plans a 24-hour count of the homeless tomorrow to quantify what many have termed an "uncountable" demographic.

Although organizers hold out hope for a successful count, an endeavor that they plan to continue on a biannual basis, the difficulties of locating much of the county's homeless population could prove a stumbling block. Because the summer heat has scattered the homeless throughout the area and into unpredictable locations, organizers and volunteers could be hampered in their efforts this week, said Gayle Sanders, director of the county's Homeless Prevention Center.

"We're going to have a great deal of difficulty because the people who were normally at the winter shelter will be out in the heat, searching for a place to be cool," Sanders said. "They'll not only be scattered but they'll be in unusual places, not where we would normally find them. In this kind of heat, they'll definitely be trying to find a place that is cool, and we won't definitely know where those places are."

Groups of volunteers plan to scour the county's shadows in search of the homeless from 7 a.m. tomorrow to 7 a.m. Tuesday, in what officials deem a "point-in-time count" of the population that will be used to gather information and to better assess Prince William's need for homeless services. Such information also translates into federal and state funding for homeless programs. Most of the tallying will be done from inspection of known homeless sites and from a count at the county's homeless shelters.

"The information obtained in this effort will assist in prioritizing the needs of the homeless population," said Dena McBride, an organizer of the count, which is coordinated by the Prince William Area Homeless Services Network Council. "After establishing need, the homeless service providers can develop the most appropriate programs to assist the homeless on the path to economic independence."

A similar survey Jan. 25 yielded a total of 309 homeless people living in the county, a mere fraction of Prince William's 270,000 residents. Homeless services officials say that the numbers are misleading because many of the homeless are hiding in unknown locations and because many shirk outreach efforts, regardless of the volunteers' tenacity.

Of the 309 homeless people who were contacted in January, 172 were adults. Of the adult population, about 52 percent were white and 35 percent black. Nearly 60 percent of the homeless surveyed were women. About 20 percent of the homeless population reported being married.

Many of the homeless children counted in January were younger than 11, with just fewer than 20 percent between ages 12 and 18.

Sanders said the survey numbers clearly do not represent the total number of homeless in the county. But the data collected, she said, can be quite useful in determing the services needed to help the homeless population.

Sanders said volunteers will provide the homeless they find tomorrow with a "survival pack," including bug spray, baby wipes, soap and other small essentials, as well as contact numbers for the county's array of social services.

"I don't expect completeness, no," Sanders said. "I still think we should be striving toward some sort of central point where we can collect this data, where even those resistant to service would go."

Sanders said the count likely will evolve over time, as organizers develop better ways to assess the homeless population.

The biannual counts were started last winter partly as a result of the public concern over a few dramatic deaths among the homeless population last year, including a campground that burned last fall in Manassas as a group of men tried to stay warm in their wooded enclave.