Ohio Winter Safety Awareness Week: Winter Watches, Advisories and Warning Criteria

Across the US, only one entity has the responsibility of issuing weather alerts – the National Weather Service. It doen’t matter if you receive your weather alerts from The Weather Channel, local television stations, radio your phone app or the Internet. All watches, warnings and advisories ORIGINATE from the NWS.

In our area the Pittsburgh NWS office is responsible for Tuscarawas, Carroll, Harrison, Coshocton, Guernsey, Muskingum and Noble Counties. NWS Cleveland is responsible for Stark, Holmes and Wayne Counties. This is important because each individual office issues weather headlines ONLY FOR THEIR COUNTY WATCH AREA (CWA). For example, the Cleveland office does not issue weather alerts for Carroll or Tuscarawas County and the Pittsburgh office will not alert Holmes or Wayne County.

Wintertime brings several weather-related headlines from NWS that apply only to winter weather. They are all issued under specific criteria and the criteria is tailored for the issuing office CWA. For example, the amount of snow that triggers a ‘Winter Storm Warning’ is typically much higher than here than it would be for a warning in North Carolina.

Knowing when each headline is issued, the criteria in our area and what the specific headline means will not only inform you of impending weather conditions but also help you make decisions and take action.

OUR MOST COMMON WINTER HEADLINE – WINTER STORM
Our most common winter weather NWS headline is for winter storms. The Pittsburgh office issues WINTER STORM WATCHES AND WARNINGS when…

(*) Snow totaling 6 inches or more within a 12 hour period OR 8 inches or more in a 24-hour period;
(*) Ice totaling one-quarter inch or more
(*) Heavy snow, heavy sleet, ice storm, blowing snow or any combination of these

Typically, NWS Pittsburgh will issue a Winter Storm WATCH 24 to 72 hours ahead of any snow or ice event that is forecast to meet the criteria. A ‘Watch’ is your heads-up notification that some nasty winter weather conditions will be POSSIBLE. You should use this notification to make preparations and modify/cancel travel plans.

A Watch is no guarantee that an event WILL happen. It simply means that weather conditions are favorable and that confidence is good that it COULD happen. Typically, certainty of an event is 50% to 80% before a Watch is issued for a particular event.

Advisories and Warnings are issued when an event is in process of happening or is about to happen very soon (probability is typically 80% or better). Warnings mean that conditions meeting the Watch criteria WILL LIKELY OCCUR or ARE CURRENTLY OCCURRING. An Advisory is for less serious weather conditions will likely occur but they may cause significant inconvenience or travel hazards.

BLIZZARDS AND ICE STORMS
These happen less frequently but blizzards and ice storms are extremely dangerous weather events – even life-threatening. A blizzard occurs when wind gusts reach or exceed 35 mph and snowfall or blowing snow reduces visibility to less than a quarter mile. And, ice storms generally mean that ice will accumulate to more than a quarter-inch. This much ice on trees and power lines almost guarantees widespread power outages for extended time.

LAKE EFFECT SNOW
We’re geographically located well downward of the Great Lakes and therefore, less susceptible to lake effect snow events. However, lake effect snow showers are not impossible here. A stiff southeast fetch off Lake Huron or Erie sometimes brings lake effect snow and squalls this far into central and southern Ohio.

Lake effect snows usually affect only limited areas within the Tuscarawas Valley and last only a short time. They can, however, put down a decent amount of snow – 3 to 6 inches – in that short time – enough to cause travel problems in the areas they occur.

Lake effect Watches and Warnings will only be issued by NWS Pittsburgh for northern Ohio and Pennsylvania counties.

WIND CHILL
Cold temperatures and wind combine to produce wind chill – how cold the temperature FEELS LIKE on skin. Wind Chill Advisories are issued when wind chills are expect to reach or exceed -10F. Wind Chill WARNINGS will be issued when wind chills are expected to reach or exceed -25F for three hours with winds at 5 mph or greater for three hours or longer.