NWS Little Rock - Watch, Warning and Advisory Criteria

Important Note: These criteria are for the National Weather Service Forecast Office in Little Rock, Arkansas. These values do not necessarily apply to other offices around the country.

Winter Storm Watch
Issued when there is the possibility of occurrence of the following weather elements, either separately or in combination:

• Snow accumulations of 3 inches or more per event in much of southern, central, and eastern Arkansas, and 4 inches or more in the north and west (including the Ozark and Ouachita Mountains).

• Freezing rain or freezing drizzle accumulations of 1/4 inch or more.

• Sleet accumulations of 1/2 inch or more.

Blizzard Warning
Issued for sustained wind or frequent gusts of 35 mph or stronger, accompanied with considerable falling and/or blowing snow, frequently reducing visibility to less than 1/4 mile, and for three hours or longer.

Ice Storm Warning
Issued when significant or possibly damaging accumulations of freezing rain and/or freezing drizzle are expected. This usually equates to accumulations of 1/4 inch or more of ice.

Snow Squall Warning
Issued when a brief period of intense snowfall (moderate to heavy in intensity) is expected, accompanied by gusty surface winds resulting in reduced visibility. One or more of the following conditions must be met:

• Visibility 1/4 mile or less in snow with sub-freezing ambient road temperatures.

• Plunging temperatures behind an arctic front sufficient to produce flash freezes, along with a significant reduction in visibility from falling and/or blowing snow.

Winter Storm Warning
Issued when there is hazardous winter weather occurring, imminent, or has a high probability of occurrence. Winter storm warnings are issued for the following conditions, whether they occur separately or in combination:

• Snow accumulations of 3 inches or more per event in much of southern, central, and eastern Arkansas, and 4 inches or more in the north and west (including the Ozark and Ouachita Mountains).

• Sleet accumulations of 1/2 inch or more.

• Freezing rain or freezing drizzle accumulations of 1/4 inch or more. (If freezing rain or freezing drizzle is not in combination with sleet and/or snow, then an Ice Storm Warning may be issued instead)

Winter Weather Advisory
Issued when the following conditions are expected, whether they occur separately or in combination:

• Snow accumulations of 1 to 3 inches. An advisory may be issued for 1 inch less if the time of year or special circumstances exist where extra caution is warranted by the forecaster (such as light snow falling on very cold roads and freezing on contact, causing significant travel hazards)

• Sleet accumulations of less than 1/2 inch.

• Freezing rain or freezing drizzle accumulations of less than 1/4 inch.

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Severe Thunderstorm Watch
Is issued by the Storm Prediction Center when conditions are favorable for the development of severe thunderstorms over a larger-scale region. Tornadoes are not expected in such situations, but isolated tornado development cannot be ruled out.

Severe Thunderstorm Warning
Issued when there is evidence based on radar or a reliable spotter report that a thunderstorm is producing, or about to produce, wind gusts of 58 mph or stronger, structural wind damage, and/or hail 1 inch in diameter or larger.

Tornado Watch
Is issued by the Storm Prediction Center when conditions are favorable for the development of severe thunderstorms and tornadoes over a larger-scale region.

Tornado Warning
Issued when there is evidence based on radar or a reliable spotter report that a tornado is imminent or occurring.

Significant Weather Advisory
Issued for strong thunderstorms that are below severe levels, but still may have some adverse impacts. Usually issued for the threat of wind gusts of 40-58 mph or hail up to 1 inch in diameter.

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Flash Flood Watch
Issued generally when there is the possibility of flash flooding or urban flooding over portions or all of the area. This product is usually issued 6 to 48  hours in advance.

Flash Flood Warning
Issued when flash flooding is occurring or imminent, generally within the next 1 to 6 hours. Usually issued based on observed heavy rainfall (measured or radar estimated), but may also be issued for significant dam breaks that have occurred or are imminent. Flash flood warnings can also be issued for excessive (but controlled) reservoir releases.

Flood Watch
Issued when there is the possibility of widespread general flooding (such as areal or river flooding) over a portion or all of the area. This product is usually issued 6 to 48 hours in advance.

Flood Warning (for river forecast point)
Issued when a river gauge has exceeded, or is forecast to exceed, a predetermined flood stage.

Flood Advisory
Issued when flooding is imminent or occurring, generally within the next 1 to 3 hours, but is not expected to substantially threaten life and property.

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Excessive Heat Watch
Issued when heat index values of 110°F or hotter are possible, or temperatures of 105°F or hotter are possible. This product is usually issued 12 to 48 hours in advance.

Fire Weather Watch
Issued when Red Flag conditions are possible in the next 12 to 72 hours.

Extreme Cold Watch
Issued when temperatures and/or wind chill values are expected to be -15°F or colder. These conditions are expected to persist for approximately 1 hour or longer.

Extreme Cold Warning
Issued when temperatures and/or wind chill values will reach -15°F or colder. These conditions are expected to persist for 1 hour or longer.

Cold Weather Advisory
Issued when temperatures and/or wind chill values will reach 0°F to -15°F. These conditions are expected to persist for 3 hours or longer.

High Wind Watch
Issued when sustained winds of 40 mph or stronger are possible for 1 hour or longer, or for non-thunderstorm wind gusts of 58 mph or stronger, with no time limit. This product is usually issued when these conditions are possible in the next 12 to 48 hours.

Dust Storm Warning
Issued when widespread or localized blowing dust is expected to reduce visibility to 1/4 mile or less, generally with sustained winds of 25 mph or stronger.

Excessive Heat Warning
Issued when heat index values are expected to reach 110°F or hotter, or temperatures of 105°F or hotter.

Freeze Watch
Issued when temperatures of 32°F or colder are possible during the growing season (locally defined and usually occurs in the late Fall or early Spring). This product is usually issued 12 to 48 hours in advance.

Freeze Warning
Issued when temperatures are expected to reach 32°F or colder in the growing season. This product is usually issued during the locally defined growing season, or to highlight the first few freezes of the fall, or unusually late freezes in the spring. This product can also be issued for over a widespread area for when the temperature will remain below 32°F for a prolonged period.

High Wind Warning
Issued when sustained winds of 40 mph or stronger are expected for 1 hour or longer, or for non-thunderstorm wind gusts of 58 mph or stronger, with no time limit.

Red Flag Warning
Issued when Red Flag conditions are occurring or imminent, and extreme fire danger conditions are expected, generally within 24 hours. Local Red Flag conditions include (all criteria must be met):

• Afternoon minimum relative humidity levels of 25% or drier

• When 20ft (above ground level) winds are 14 mph or stronger

• Fuel moisture levels are critically low, determined in coordination with USDA Forest Service (usually less than 10% fuel moisture levels for 10 hour fuels)

Dense Fog Advisory
Issued when fog is expected to reduce visibilities to 1/4 mile or less over a widespread area.

Freezing Fog Advisory
Issued when very light ice accumulations are expected from freezing fog, causing hazardous driving conditions.

Frost Advisory
Issued when frost is expected with nighttime minimum temperatures ranging from 33°F to 36°F in the growing season (locally defined and usually only issued in the late Fall or early Spring).

Heat Advisory
Issued when heat index values are expected to reach 105°F or hotter, or the temperature of 103°F or hotter.

Wind Advisory
Issued when sustained winds are 25 mph or higher (excluding gusts) for at least an hour.

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