WAUWATOSA, WI (WTAQ) - This week’s snowstorm has created a major shortage of blood.

The Blood Center of Wisconsin said lots of appointments for blood donations were canceled Thursday.

As a result, the center expects a shortfall of over 1,000 units over the next several days. All blood types are needed, but officials say there’s a particular need for “O”-Negative – the universal type that’s used in emergency rooms and med-flight helicopters.

The Blood Center also has a critical need for platelets, which are used to help cancer and trauma patients recover from life-threatening injuries.

The Blood Center serves 56 hospitals in Wisconsin. It’s asking everyone to keep their scheduled appointments if they can safely do so – and others who wish to help can make appointments for Saturday, Sunday, and Monday.

The Blood Center’s Wauwatosa location will have extended hours Saturday – and only platelet donors can make appointments for Sunday at the ‘Tosa site.