Monday, July 28, 2014

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What is the difference between a watch and a warning?

A watch alerts you to potential severe weather approaching your area. It doesn't mean severe weather will occur, but that the right conditions exist which could lead to severe storms. You should be prepared for the weather to deteriorate rapidly.

A warning states the severe weather is imminent or present in your vicinity. You should immediately take precautions to protect yourself and your family. Be sure to read the safety guide for advice on what to do when severe weather strikes the northeast.

Log on to our site or tune in to our news channel when severe weather strikes to receive watches, warnings and advisories from the National Weather Service. Be sure to tune in during alerts for up-to-the-minute, live forecasts and for your area.

Here is what the different advisories mean:

BLIZZARD WARNING

Is issued for a combination of strong winds with frequent gusts of 35 mph and greater along with very low visibility due to blowing or falling snow.

BLIZZARD WATCH

Is issued in advance for the potential of very strong gusty winds of 35 mph or greater combined with blowing or falling snow.

BLOWING SNOW ADVISORY

Is issued when the visibility will be significantly reduced or when the roads become snow covered over a large area.

DENSE FOG ADVISORY

Is issued when widespread fog is expected to reduce visibilities to 1/4 mile or less for more than three hours.

FLASH FLOOD/FLOOD WARNING

Is issued when flooding is being reported or is imminent. Take necessary precautions at once. You may only have seconds!

FLASH FLOOD/FLOOD WATCH

Is issued when flooding is possible within the designated area. It is issued in advance to give people the time to move property and livestock to higher ground. Be alert!

FLOOD ADVISORY

Is issued by the National Weather Service when there is a potential for periods of heavy causing flood problems. An ADVISORY

Will be issued well in advance of the flood threat.

FOG ADVISORY

Is issued when fog will reduce visibility significantly causing potential travel hazards.

FREEZE ADVISORY

Is issued when there is a potential in the next few days of the temperatures dropping to below 32 degrees. It is issued to give people time to take necessary precautions.

FREEZE WARNING

Is issued when the temperature is expected to fall below 32 degrees for three hours or greater. The WARNING is issued in advance of the freeze in order to give people time to protect tender vegetation, pipes and other exposed objects.

FREEZING DRIZZLE ADVISORY

Is issued in advance for the potential of freezing drizzle causing an accumulation of ice on exposed surfaces, including roads, power lines and trees. Freezing Drizzle is drizzle that freezes upon impact because the air temperature is below 32 degrees.

FREEZING RAIN ADVISORY

Is issued in advance for the potential of freezing rain causing an accumulation of ice on exposed surfaces, including roads, power lines and trees. Freezing Rain is rain that freezes upon impact because the air temperature is below 32 degrees.

FROST ADVISORY

Will be issued when the potential of high humidity and falling temperatures below 32 degrees leaves a thin coat of ice on exposed surfaces.

FROST WARNING

Is issued when the formation of frost, or a thin layer of ice crystals, will coat surfaces. Frost develops similar to dew when the temperature falls below 32 degrees.

FROST/FREEZE ADVISORY

Is issued for the potential of temperatures falling below 32 degrees and the humidity being high enough to create a thin layer of ice or ice crystals on exposed surfaces.

HEAT ADVISORY

Is issued between May 1 and June 30 when the Heat Index, a combination of the air temperature and the humidity, is forecast to be 98 to 105 degrees for one day or longer. It is issued between July 1 and September 30 when the heat index is forecast to be 100 to 110 degrees for one day or longer.

HEAT WARNING

Is issued by the National Weather Service when the Heat Index, a combination of the actual air temperature and humidity is expected to exceed 115 degrees during any length of time during the day.

HEAVY SNOW WARNING

Is issued for snowfall of between four and seven inches in a 24-hour period.

HEAVY SNOW WATCH

Will be issued when the potential exists for snowfall of between four and seven inches in a 24-hour period. This WATCH will be issued at least 12 hours in advance of potentially heavy snow.

HIGH WIND ADVISORY

Is issued when the weather service feels there is a threat in the next few days of possible sustained winds of 40 mph or greater and/or sustained gusts of 57 mph or greater.

HIGH WIND WARNING

Is issued when winds will average 35 to 40 mph or greater and/or wind gusts will be greater than 57 mph or greater for one hour.

HIGH WIND WATCH

Is issued in advance of possible sustained winds of 40 mph or greater and/or gusts of 57 mph or greater. The WATCH may be issued up to 12 hours in advance of these wind speeds.

ICE STORM WARNING

Is issued when freezing rain or freezing drizzle will leave accumulated ice on roadways, power lines, trees and other exposed objects.

LAKE EFFECT SNOW ADVISORY

Will be issued when there is a potential for lake effect snowfall accumulation to seven inches or more within a 12-hour period.

LAKE EFFECT SNOW WARNING

Is issued when heavy lake effect snow is occurring or is approaching, or has the probability of occurring in the next 12 hours. Snow accumulations of seven inches along with strong winds will be the main effects.

LAKE EFFECT SNOW WATCH

Is issued for the possibility of heavy lake effect snow accumulation to seven inches or greater. This WATCH will be issued at least 12 hours in advance of potentially heavy snow accumulations.

RIVER FLOOD WARNING

Is issued when flooding is occurring or is imminent at one or more forecast points along a river.

SEVERE THUNDERSTORM WARNING

Is issued when severe thunderstorms are occurring or about to move in to the area. Get to a safe place immediately.

SEVERE THUNDERSTORM WATCH

Is issued when thunderstorms produce any and all of the following weather features: Hail 3/4" in diameter or larger, wind gusts to 58 mph or greater and/or tornadoes.

Thunderstorms producing the following may occur in your area:


  • Hail ¾" in diameter or larger, wind gusts 58 mph or greater and/or tornadoes.

  • Wind gusts 58 mph or greater and/or tornadoes.

  • Frequent lightning and flash flooding may also accompany severe thunderstorms.


SNOW ADVISORY

Is issued when the National Weather Service feel that a certain area may receive significant accumulations over a 12-hour period.

TORNADO WARNING

Is issued when a tornado has been sighted or indicated by weather radar and/or the Skywarn spotter network. Tornado Warnings are issued by the National Weather Service. When a Tornado Warning is issued where you live you should get to a safe place immediately.

Fujita Wind Damage Scale
F0:Up to 72 mphLight Damage
F1:73 - 112 mphModerate
F2:113 - 157 mphConsiderable
F3:15 - 206 mphSevere
F4:207 - 260 mphDevastating
F5:Above 261Incredible

TORNADO WATCH

Is issued in advance of possible tornadoes and severe thunderstorms. Continue with your normal routine but remain alert for approaching storms.

URBAN SMALL STREAM FLOOD ADVISORY

Is issued when local flooding of small streams, streets or low-lying areas such as railroad underpasses is occurring or imminent.

WIND ADVISORY

Is issued when there is a potential of sustained winds of 25 to 39 mph and or sustained gusts of 40 to 56 mph during a given time period.

WIND CHILL ADVISORY

Is issued when the combination of cold temperatures and wind is computed to be -25 degrees or less for at least three hours.

WIND CHILL WARNING

Is issued when winds will combine with cold temperatures to create dangerously cold conditions for exposed skin. Frostbite and hypothermia can occur. Limit time outdoors. When you do go, dress in layers and cover all exposed skin.

WINTER STORM ADVISORY

Will be issued by the National Weather Service when there is a possibility that some type of winter weather will occur in the next few days. The weather types would be snow, sleet and/or freezing rain or freezing drizzle.

WINTER STORM WARNING

Is issued when the threat for snow of seven inches or greater in a 24-hour period OR accumulations of ice due to freezing rain or freezing drizzle will down trees and powerlines.

WINTER STORM WATCH

Is issued when there is a threat of winter weather due to heavy snow, sleet or ice accumulations on trees and power lines. The WATCH is issued at least 12 hours in advance of possible severe winter weather.

WINTER WEATHER ADVISORY

Is issued for a combination of of snow, sleet and/or freezing rain. The ADVISORY is issued in advance of a possible winter weather event that will cause roads to become slippery and to alert motorists that travel is not recommended.

What do the sky conditions tell us?

The average sky cover is part of our daily forecast. This percentage is the amount of sky expected to be covered by opaque clouds, the type that do not allow other clouds, or blue sky to be visible. The following table lists descriptive terms for sky conditions:

TERMINOLOGYAVERAGE SKY COVER
Cloudy90-100 percent
Mostly cloudy70-80 percent
Partly Cloudy/Partly Sunny30-60 percent
Mostly Clear/Mostly Sunny10-30 percent
Clear/Sunny0-10 percent
FairFew clouds and no precipitation or extreme weather


How do you make up the chances for rain?

The forecast for the probability of precipitation is one of the least understood elements of forecasting. The probability of precipitation has the following features:


-The likelihood of precipitation is stated as a percentage
-A measurable amount is defined as .01" (one hundredth of an inch) or more. More than .01" usually produces enough runoff for puddles to form
-The probability is for a specified time period
-The probability forecast is for any point in the forecast area

What are the Moon Phases?

New Moon

When the Moon is not illuminated by direct sunlight.

Waxing Crescent

Occurs when the visible Moon is partly but less than one-half illuminated by direct sunlight while the illuminated part is increasing.

First Quarter

When one-half of the Moon appears illuminated by direct sunlight while the illuminated part is increasing.

Waxing Gibbous

When the Moon is more than one-half but not fully illuminated by direct sunlight while the illuminated part is increasing.

Full Moon

When the visible Moon is fully illuminated by direct sunlight.

Waning Gibbous

The Moon is less than fully but more than one-half illuminated by direct sunlight while the illuminated part is decreasing.

Last Quarter

Is when one-half of the Moon appears illuminated by direct sunlight while the illuminated part is decreasing.

Waning Crescent

Occurs when the Moon is partly but less than one-half illuminated by direct sunlight while the illuminated part is decreasing.

What do those weather terms in the forecast mean?

Atmosphere

The envelope of air surrounding the planet earth. The atmosphere extends from the ground to about 180 miles above the planet.

Atmospheric models

Simulation of the atmosphere's behavior by mathematical equations or by physical models. We display this information using Precisioncast.

Ceiling

The height of the lowest layer of clouds.

Climate

The average of daily and seasonal weather over a long period of time, often 30 years

Cold Front

The leading edge of a cold air mass advancing into a warm air mass

Dew Point

The temperature to which air must be cooled to in order for dew (or frost) to form

El Niño

An extensive warming that begins along the coast of Peru and Ecuador; occurs once every 3 to 7 years. El Nino refers to "the time of your (Christmas) which these countries notice changes in fishing". El Nino means "the little boy" - which refers to the Christ Child.

Fog

A cloud with its base at the Earth's surface

Funnel Cloud

Often the initial phase of a tornado, it's a rotating column of air extending from a cloud but not reaching the ground

Heat Index

An index that combines the air temperature and relative humidity to determine an apparent temperature - how it really feels to the human body

High

A region of air with higher-than-normal barometric pressure, around which winds blow clockwise. Usually associated with fair weather

Heat Lightning

Ordinary lightning that is too far away for its thunder to be heard; a misnomer.

High

A region of air with higher barometric pressure than the area surrounding it, around which winds rotate clockwise; usually associated with fair weather

Hurricane

The largest storm system on the planet, it's the most powerful tropical system with winds of 74 mph or more.


Saffir-Simpson Damage Scale
Wind SpeedsStorm Surge
Category 174-95 mph4-5 Feet
Category 296-110 mph6-8 Feet
Category 3111-130 mph9-12 Feet
Category 4:131-155 mph13-18 Feet
Category 5156+ mphMore than 18 Feet

Jet Stream

Strong winds at about 35,000 feet aloft that divide air masses of different temperatures, and often act as steering currents for weather systems

La Niña

Condition where the central and eastern tropical Pacific Ocean waters turn cooler than normal. Opposite of El Nino!

Low

A region of air with lower barometric pressure then the area surrounding it that rotates counter-clockwise; usually associated with stormy weather

Meteorology

The study of the atmosphere and atmospheric phenomena as well as the atmosphere's interaction with the Earth's surface, oceans and life in general

NEXRAD

An acronym for Next Generation Weather RADar, the main component of NEXRAD is Doppler radar.

Precipitation

Any form of water particles - liquid or solid- that falls from the atmosphere and reaches the ground

Relative Humidity

The ratio of the amount of water vapor in the air compared to the amount of water vapor the air (at a certain temperature) can hold

Showers

Precipitation which comes and goes at an unsteady rate, could be rain or snow.

Stationary Front

A boundary separating two air masses that shows little or no movement

Tornado

The most violent of all storms, it's a strong, rotating column of air extending from the base of a cumulonimbus cloud to the ground

Tropical Depression

A tropical cyclone with maximum sustained winds near the surface of less than 39 mph

Tropical Storm

Tropical cyclone with 39 to 73 mph sustained winds; it's just one step below hurricane status.

Tropical Wave

A disturbance moving off the western coast of Africa toward the Caribbean and eastern North American coastal regions which may eventually develop into a hurricane.

Warm Front

The leading edge of a warm air mass advancing onto a cold air mass

Weather

The condition of the atmosphere at any particular time and place

Wind Chill

The cooling effect of the combination of temperature and wind, expressed as the loss of body heat

Be sure to read the Storm Safety tips so you will be prepared in case of severe weather.

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