National Weather Service United States Department of Commerce

Watch versus Warning

⚠️ Watch: Severe thunderstorms and/or tornadoes may develop. Prepare now!

🚨 Warning: A severe thunderstorm and/or tornado is happening or imminent. Take action now!

🔗 For thunderstorm safety tips and resources, visit



Severe Thunderstorm Watch [SV.A]

  • Issued when conditions are favorable for the development of thunderstorms which contain winds of at least 58 mph and/or hail 1 inch or larger.

Tornado Watch [TO.A]

  • Issued when conditions are favorable for thunderstorms to produce tornadoes.



Severe Thunderstorm Warning [SV.W]

  • Thunderstorm winds of 58 mph or greater and/or hail 1 inch in diameter or greater.

Tornado Warning [TO.W]

  • A tornado is spotted or detected on radar.



Significant Weather Advisory [SPS]

  • Gusty winds less than 58 mph and/or small hail less than 1 inch below Severe Thunderstorm Warning thresholds. These storms may strengthen to prompt the issuance of a Severe Thunderstorm Warning.


⚠️ Turn around, Don't drown! ⚠️

🔗 For flood safety tips and resources, visit



Flash Flood Watch: [FF.A]

  • Potential for flash flooding due to non-convective causes (e.g., dam or levee failure or ice jam), or the possibility of flash flooding and debris flows caused by excessive rainfall on burn scars or in debris flow- and landslide-prone areas.

Flood Watch: [FA.A]

  • Conditions are favorable for flooding caused by excessive rainfall and runoff. As of 2021, this combines what was formerly (convective) Flash Flood Watches and Areal Flood Watches.

River Flood Watch: [FL.A]

  • Issued for river forecast points when river flooding is possible, but flooding is not expected to begin within the next 24 hours.



Flash Flood Warning: [FF.W]

  • Short duration (usually less than six hours), flash flooding resulting from storms with rainfall rates of 1 to 2 inches per hour or greater. Also issued when a dam has failed or when a dam failure is imminent.

(Areal) Flood Warning: [FA.W]

  • Long duration (slow to evolve), flooding resulting from steady stratiform rain with rates typically less than 1 inch per hour. Most common during long duration spring rains resulting in widespread flooding.

River Flood Warning: [FL.W]

  • River flooding is occurring or is forecast for a point. Normally issued when flooding is forecast within 24 hours based on accumulated rainfall.



Flood Advisory: [FA.Y]

  • Localized flooding resulting from heavy rain. Water may start to threaten homes and businesses, and minor flooding of roads is possible


⚠️ Prepare for Winter Weather Hazards! ⚠️

🔗 For winter safety tips and resources, visit



Winter Storm Watch: [WS.A]

  • Potential for a blizzard, heavy snowfall, or ice storm within the next 18 to 48 hours. Issued when there is a 50% confidence or greater of at least 6 inches of snow and/or a ¼ inch of ice.

Wind Chill Watch: [WC.A]

  • Wind chill -25ºF or colder with wind speeds 5 mph or greater for at least 3 hours within the next 18 to 48 hours.



Winter Storm Warning: [WS.W]

  • Snow accumulations 6 inches or greater; Freezing rain accumulations ¼ inch or greater.

Blizzard Warning: [BZ.W]

  • Sustained winds 35 mph or greater AND falling/blowing snow reducing visibility to less than ¼ mile for at least three hours.

Ice Storm Warning: [IS.W]

  • Freezing rain accumulations ¼ inch or greater resulting in significant, widespread power outages, tree damage, and dangerous travel.

Lake Effect Snow Warning: [LE.W]

  • Lake effect snow accumulations 6 inches or greater in 12 hours (8 inches or more in 24 hours). This is issued only for northernmost portions of our area.

Snow Squall Warning: [SQ.W]

  • A short-duration (less than 1 hour), polygon-based warning issued when strong snow squalls and flash freezing will cause dangerous and life-threatening conditions, espectially for roadways. Usually issued when ground/road temperatures are sub-freezing and visibility is less than ¼ mile.

Wind Chill Warning: [WC.W]

  • Wind chill of -25ºF or colder with wind speeds 5 mph or greater for at least 3 hours.



Winter Weather Advisory: [WS.Y]

  • Snow accumulations of 3 inches, any freezing rain accumulations less than ¼ inch, or a high impact snow/ice event.

Wind Chill Advisory: [WC.Y]

  • Wind chill -10ºF to -25ºF for at least 3 hours.


⚠️ Practice Heat Safety when outdoors! ⚠️

🔗 For Heat Safety tips and resources, visit



High Wind Watch: [HW.A]

  • Conditions are favorable for development of sustained winds of 40 mph or greater and/or gusts of 58 mph or greater within the next 24 to 48 hours.

Freeze Watch: [FZ.A]

  • Potential for the first freeze of the fall season or for a late spring freeze within the next 18 to 24 hours. Product is discontinued for the season following the first fall "killing" freeze.

Excessive Heat Watch: [HT.A]

  • Potential for heat index values of 105ºF or hotter within the next 24 to 48 hours.



High Wind Warning: [HW.W]

  • Non-convective sustained wind speeds 40 mph and greater and/or wind gusts 58 mph and greater.

Freeze Warning: [FZ.W]

  • When temperatures will be at or below 32ºF over a large area for a significant time during the growing season.

Excessive Heat Warning: [HT.W]

  • Heat Index of 105ºF or greater.

Red Flag/ Fire Weather Warning: [FW.W]

  • Dangerous fire behavior expected within the next 12-24 hours based on weather conditions and dry fuels.



Wind Advisory: [WI.Y]

  • Non-convective sustained wind speeds 30-39 mph with wind gusts 46-57 mph.

Frost Advisory: [FR.Y]

  • When frost is expected during the growing season.

Heat Advisory: [HY.Y]

  • Heat Index of 100ºF to 104ºF.

Dense Fog Advisory: [FG.Y]

  • Fog reducing visibilities to a ¼ mile (0.4 km) or less for at least 3 hours.


*Please note: winter and heat related criteria are based on local climatology. Therefore, NWS Pittsburgh area thresholds for heat and winter related products may differ slightly from neighboring NWS offices' criteria.