text: Some operations have been cancelled and extra staff drafted in to deal with a surge of patients over the weekend.
  The Bristol Royal Infirmary, Southmead Hospital and Weston General hospitals are affected.
  More beds are being opened but people are urged not to go to A&E unless they have a "life-threatening" condition.
  Instead they are urged to go to minor injury units, chemists and GP surgeries, or to call the NHS on 111.
  A black alert, the highest level, means hospital services are unable to cope with demand. The three hospitals were last on black alert earlier this month.
  The number of people in hospital for more than two weeks is much higher than usual, said an NHS spokesman.
  A surge of patients during last week's cold snap has added to pressure.
  The black alert is likely to stay in place for days. Extra ambulance staff are being used to transfer patients into hospital, to prevent ambulances queuing and district nurses are being deployed to hospitals, to help find community beds for patients well enough to leave.
  Bristol GP Peter Goyder said an increase in hospital admissions together with "a higher number of very ill patients who need to stay in hospital for longer" had contributed to the situation.
  Analysis of the most recent figures suggests hospitals in England are struggling to meet the four-hour target for treating or admitting 95% of patients.
  Three hospitals in Cornwall also went on black alert this month, as did two in Somerset.
target: Hospitals with A&E departments around Bristol are back on black alert for the second time in a month amid "severe pressure" on services.