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EMERGENCY MANAGEMENT | Box 4117 | Gaithersburg, MD 20878
240-777-2300 (voice) | 240-777-2345 (fax)

When a winter storm threatens our area, the local weather forecasts will contain a variety of terms for watches/warnings/advisories and precipitation types. The following is a list of the commonly used terms for winter forecasts. hen a winter storm threatens our area, the local weather forecasts will contain a variety of terms for watches/warnings/advisories and precipitation types. The following is a list of the commonly used terms for winter forecasts.

• WATCHES/WARNINGS: Issued for life-threatening weather conditions.

• WINTER STORM WATCH: Issued when at least four inches of snow in 12 hours, or at least six inches in 24 hours, or significant ice accumulations are possible within 12 hours.

• BLIZZARD WARNING: Issued when snow and strong winds will combine to produce low visibility, deep snow drifts, and dangerously low wind chills.

• ADVISORIES: Issued for weather conditions that are hazardous, but not necessarily life threatening.

• SNOW ADVISORY: Issued when one to three inches of snow is expected to accumulate within 12 to 24 hours.

• FREEZING RAIN/DRIZZLE ADVISORY: Issued when freezing rain/drizzle will produce hazardous, but not life threatening, conditions for motorists and pedestrians.

• WINTER WEATHER ADVISORIES: Issued when a variety of winter weather precipitation will cause significant inconvenience and may be hazardous, but probably not life threatening.

Precipitation Terms:

• SNOW: A steady fall of snowflakes for several hours or more.

• SNOW SHOWER: Snow falling at varying intensities for brief periods of time. Some light accumulation is possible.

• SNOW FLURRY: Light snow falling for short duration's and resulting in no accumulation.

• BLOWING SNOW: Wind-driven snow that reduces viability and causes significant drifting. Blowing snow may be loose snow picked up by the wind from the ground.

• SLEET: Raindrops that freeze into ice pellets before reaching the ground. Sleet usually bounces when hitting a hard surface. Long periods of falling sleet can result in a minor accumulation and cause hazard to motorists.

• FREEZING RAIN DRIZZLE: Rain/drizzle with temperatures that are below freezing that strikes a surface, such as a road, bridge, sidewalk, tree, or car. The rain/drizzle freezes instantly on impact, forming a layer of ice.

Common Winter Storm Labels

• NOR'EASTER: An intense area of low pressure that forms along or near the East Coast and rapidly intensifies as it moves toward the north or northeast. These storms are known for producing strong northeast winds, coastal flooding, beach erosion, and heavy precipitation along the U.S. East Coast. These storm systems are also called "winter hurricanes".

• ALBERTA CLIPPER: A name for a fast moving low pressure system that forms over or near the province of Alberta, Canada and tracks south and east across the northern tier of the U.S. This storm brings storm winds and cold air, but not much snow.

• ICE STORM: A label for damaging accumulations of ice resulting from a lengthy period of freezing rain. Significant ice accumulations are usually 1/4 inch or greater.

• SNOWSTORM: A label for a heavy snowfall event. The term is used for events in which at least four inches of snow will fall during a 12 hour period, or six inches will fall during a 24 hour period. Strong winds may accompany the snowfall to produce blowing snow and low wind-chill.

The terms listed above are commonly used in winter season weather forecasts and statements. Understanding the meaning of these forecast terms is very important when determining what weather conditions are expected in the local area.