In Central Pennsylvania not every county has the same criteria needed when it comes to issuing winter Watches, Warnings and Advisories. Here, we have two National Weather Service offices responsible for issuing these alerts, one in Pittsburgh, and one in State College.
A Winter Storm Warning is issued when the N-W-S expect at least 6 inches of snow to fall within 12 hours or 8 inches of snow to fall within 24 hours.
A Winter Storm Watch is issued 24-48 hours in advance if they believe that the warning criteria will be met. A Winter Storm Advisory is issued if 3-5 inches of snow falls within 12 hours.
A Blizzard Warning IS issued if the winds are 35 mph or greater with considerable falling OR blowing snow that cuts the visibility down to less than 1/4 of a mile. These conditions must last for at least 3 hours.
Where counties differ in criteria is when an Ice Storm Warning is issued. Blair, Bedford, Cambria, Centre, Clearfield, Jefferson and Somerset counties must receive 0.25 inches of ice where Cameron and Elk need 0.50 inch of ice.
A Freezing Rain Advisory will be issued if a trace amount is expected to fall over Central PA.