National Weather Service United States Department of Commerce

Atmospheric River to Impact the Northwest; Windy Conditions in the Northeast

A strong atmospheric river moving into northern California later today will bring a threat for moderate to heavy rainfall and flooding, gusty to high winds, and mountain snows for parts of the Northwest U.S. through Wednesday. Gusty winds and isolated showers are expected today in the Northeast U.S. behind a cold front. Wind Advisories have been issued. Read More >

 

Summer Briefing

 

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Summer Weather Definitions

Tornado or Severe Thunderstorm WATCH:

Conditions are favorable for the development of tornadoes, large hail, and/or damaging winds.

 
Tornado WARNING:

A tornado has been detected on radar or sighted by trained spotters.

 
Severe Thunderstorm WARNING:

A severe thunderstorm has been detected on radar or reported by trained spotters. A severe thunderstorm is a storm that produces hail 1 inch or larger and/or winds 58 mph or greater

 
Severe Thunderstorm Outlook Terms:
  • Marginal Risk:

    Isolated severe thunderstorms are possible.

  • Slight Risk:

    Scattered or short-lived severe thunderstorms are possible.

  • Enhanced Risk:

    Numerous or persistent severe thunderstorms are possible.

  • Moderate Risk:

    Widespread, long-lived, and intense severe thunderstorms are likely.

  • High Risk:

    Widespread, long-lived, and particularly intense severe thunderstorms are expected.

Flood WATCH:

Conditions are favorable for flooding.

 
Flash Flood WARNING:

Life-threatening flooding is detected on radar, indicated by stream gauges, or reported by storm spotters. A flash flood is a flood that occurs very quickly; it is caused by heavy rainfall over a short period of time or from a dam break.

 
Flood WARNING:

Rivers overflowing their banks or water covering a normally dry area. Floods are usually caused by heavy rain over a long period of time, rapidly melting snow, or ice jams.

 
Extreme Heat WARNING:

Heat index 105 degrees or higher, with a minimum heat index of 75 degrees for 48 hours or longer; or heat index of 100 degrees or higher for four consecutive days.

 
Heat ADVISORY:

Heat index 100 degrees or higher; or heat index between 95 and 100 degrees for four consecutive days.