A severe thunderstorm warning ( SAME code: SVR) is a type of public warning for

severe weather Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. These vary depending on the latitude, altitude, topography, and atmospheric conditions. High ...

that is issued by

weather forecasting Weather forecasting or weather prediction is the application of science and technology forecasting, to predict the conditions of the Earth's atmosphere, atmosphere for a given location and time. People have attempted to predict the weather info ...

agencies worldwide when one or more

severe thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...

s have been detected by

Doppler weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pu ...

, observed by weather spotters, or reported by an

emergency management Emergency management (also Disaster management) is a science and a system charged with creating the framework within which communities reduce vulnerability to hazards and cope with disasters. Emergency management, despite its name, does not actu ...

agency, law enforcement, or the general public. Unlike a watch, a warning is issued to areas in the direct path of active severe thunderstorms, that are expecting a direct impact typically within an hour. Severe thunderstorms can cause property damage and injury due to large

hail Hail is a form of solid Precipitation (meteorology), precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailsto ...

, high winds, and

flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

ing due to torrential rainfall. The exact criteria to issue a warning varies from country to country. In the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, the

National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...

issues a warning when an observed thunderstorm is producing wind gusts of at least , or hail of at least in diameter. Most forecasting agencies have similar criteria, but some agencies, such as

Environment Canada Environment and Climate Change Canada (ECCC; )Environment and Climate Change Canada is the applied title under the Federal Identity Program; the legal title is Department of the Environment (). is the Ministry (government department), department ...

, also include high rainfall rate. Others may instead issue a flood advisory or in the case of the National Weather Service, a flash flood warning.

Definition

A severe thunderstorm warning indicates the warned area is in impending danger from hail or wind speeds meeting warning criteria as well as from lightning and hydrological impacts associated with the

storm cell A storm cell is an air mass that contains up and down vertical draft, drafts in convective loops and that moves and reacts as a single entity, functioning as the smallest unit of a storm-producing system. An organized grouping of thunder clouds wi ...

. Severe thunderstorms can and occasionally do produce tornadoes without warning. While not all severe thunderstorms produce tornadoes, they can produce serious straight line wind damage as severe as a lower-category tornado or hurricane, and can actually cover a much wider area than that exceeded by a tornado's comparatively narrow path width. If a tornado is detected on radar or is sighted visually, a tornado warning will be issued either in replacement of or concurrently to the existing severe thunderstorm warning. Generally, but not always, a severe thunderstorm watch or tornado watch (or a regional equivalent thereof) will precede a warning. If a tornado warning is issued, based on Doppler

weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation (meteorology), precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern w ...

, it means strong rotation has been detected within a thunderstorm. Usually, if a thunderstorm is producing only weak rotation, it will only yield hazardous weather warranting a severe thunderstorm warning. However, the public will usually be advised this type of rotation has been detected and that the storm in question should be watched closely in the near future for further intensification.

Regional basis and criteria

United States

In the United States, the

(NWS) defines a severe thunderstorm as having large hail of in diameter or larger, surface

wind speed In meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer. Wind spe ...

s of or greater, and/or a

tornado A tornado is a violently rotating column of air that is in contact with the surface of Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the ...

. Prior to January 2010, the hail size for which a thunderstorm would be considered severe was ; public complacency due to overly frequent issuances of severe thunderstorm warnings and recent studies stating hail did not produce significant damage on the ground until it reached one inch in diameter caused the upgrade in hail criteria. Severe thunderstorm warnings are issued by the National Weather Service through the agency's local Weather Forecast Offices, which utilize WarnGen software integrated into the Advance Weather Interactive Processing System ( AWIPS) to generate the warning statement; it is then disseminated through various communication routes accessed by the media and various agencies, on the internet, to

NOAA The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...

satellites, over

NOAA Weather Radio NOAA Weather Radio (NWR), also known as NOAA Weather Radio All Hazards, is an automated 24-hour network of Very high frequency, VHF Frequency modulation, FM weather radio stations in the United States which broadcast weather information direct ...

and, depending on the storm's severity and at the office's discretion, via activation of the

Emergency Alert System The Emergency Alert System (EAS) is a Emergency population warning, national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via Cable television, cable ...

to local broadcast media and Wireless Emergency Alerts for cellular phones. Local NWS forecast offices outline warnings for tornadoes and severe thunderstorms in

polygon In geometry, a polygon () is a plane figure made up of line segments connected to form a closed polygonal chain. The segments of a closed polygonal chain are called its '' edges'' or ''sides''. The points where two edges meet are the polygon ...

al shapes for map-based weather hazard products distributed to the main agency, individual forecast office websites and the

Storm Prediction Center The Storm Prediction Center (SPC) is a US government agency that is part of the National Centers for Environmental Prediction (NCEP), operating under the control of the National Weather Service (NWS), which in turn is part of the National Oceani ...

(including open-source

API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...

s available for free use to public weather websites and mobile apps), based on the storm's projected path as determined by

at the time of the warning's issuance. In NWS text products, warnings are usually illustrated by individual

counties A county () is a geographic region of a country used for administrative or other purposesL. Brookes (ed.) '' Chambers Dictionary''. Edinburgh: Chambers Harrap Publishers Ltd, 2005. in some nations. The term is derived from the Old French denoti ...

parishes A parish is a territorial entity in many Christian denominations, constituting a division within a diocese. A parish is under the pastoral care and clerical jurisdiction of a priest, often termed a parish priest, who might be assisted by one or ...

or other county-equivalent jurisdictions (sections or the entirety thereof, and in list format if it covers more than one jurisdiction), particularly dependent on the jurisdiction's total land area. Prior to October 2007, warnings were issued by the National Weather Service on a per-county basis. SPC and NWS products, as well as severe weather alert displays used by some television stations, typically highlight severe thunderstorm warnings with a yellow or orange polygon or filled county/parish/equivalent jurisdiction outline. The NWS has the option of adding enhanced wording to severe thunderstorm warnings and update statements issued as a Severe Weather Statement (SVS)—" particularly dangerous situation" (PDS), "severe thunderstorm emergency", or, as used by some Central and Southern Region offices as indicative PDS wording, "this is a very dangerous storm"—when an extremely intense severe thunderstorm expected to impact a densely populated area contains very large hailstones and/or intense straight-line winds capable of causing major structural damage (especially to roofs, windows, siding and structures of poor construction such as outbuildings and

mobile home A mobile home (also known as a house trailer, park home, trailer, or trailer home) is a prefabrication, prefabricated structure, built in a factory on a permanently attached chassis before being transported to site (either by being towed or ...

s), and severe injury if not death to people and animals exposed outdoors (from either repeated hail-induced

blunt trauma A blunt trauma, also known as a blunt force trauma or non-penetrating trauma, is a physical trauma due to a forceful impact without penetration of the body's surface. Blunt trauma stands in contrast with penetrating trauma, which occurs when a ...

or wind-generated

debris Debris (, ) is rubble, wreckage, ruins, litter and discarded waste, garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can ref ...

). Although it is an unofficial alert product, a "severe thunderstorm emergency" statement—an extension of the tornado emergency statements issued to warn of a violent tornado impacting populated areas—is the highest and most urgent level relating to non-tornadic severe thunderstorms. When a threat of tornadic activity exists (especially if a tornado watch is in effect), local NWS forecast offices, particularly those in the

Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...

or Southeastern U.S., will sometimes include a safety precaution action statement indicating "Severe thunderstorms can produce tornadoes with no advance warning..." or similar wording in their severe thunderstorm warnings to advise the public to keep abreast of possible tornado development and any tornado warnings that may be issued. As part of the agency’s March 2012 implementation of a multi-tier Impact Based Warning (IBW) system to notify the public and emergency management officials of the severity of specific severe weather phenomena, National Weather Service-issued severe thunderstorm warnings and associated Severe Weather Statements providing updated storm information include event tags at the bottom of the product text providing summarical estimates of straight-line wind speeds (sustained or gusts) and hail size and, when applicable, an indication of possible tornadic development. The product text will also provide a summary of impacts to life and property that may be caused by the hailstones and winds being produced by the parent thunderstorm. Initially implemented at six NWS offices in Kansas and Missouri, the categorical threat and damage indicator text—which are applicable to all of the agency’s Weather Forecast Offices, primarily those operating within the agency's Central and Southern Region divisions—were expanded to 33 additional Central Region WFOs in March 2013; eight additional offices operating within the Eastern, Southern and Western Region divisions began using the IBW indicators in March 2014. The entire agency began using the format in 2016. The threat indicators consist of three coded taglines, ascending by observational level: * Tornado – indicates the mesocyclone of the parent severe thunderstorm is producing circulation at or near the cloud base, which may warrant the issuance of a tornado warning if base-level rotation strengthens. When incorporated into the storm impact summary, the tornado tag (appearing in applicable severe thunderstorm warning products as “TORNADO...POSSIBLE”) will precede the wind and hail tags. * Hail – indicates the estimated size of hail (measured in inches) being produced by the parent severe thunderstorm (e.g., “HAIL...1.25IN”). When included, the “Impact” section of the warning text will describe potential damage impacts from the hailstones, with the impact message varying in severity depending on radar estimated or observed reports of measured large hail (e.g., “Hail damage to vehicles is expected.”) and the “Hazard” section will provide a comparison of the size of hailstones to objects of similar size (e.g., “baseball size hail” for hailstones measuring 2.75"). (If the tag lists either “HAIL...0.00IN”, indicating no hail is accompanying the storm, or “HAIL...<.75IN”, indicating hailstones below severe criteria that may range in equivalent size from peas 25"to pennies 75" no hail size will be indicated in the “Hazard” row nor will a description of damage risk be included in the “Impact” section.) * Wind – indicates estimated speed (in miles per hour) of wind gusts produced by the parent thunderstorm (e.g., “WIND...70MPH”). When included, the “Impact” section of the warning text will describe potential damage impacts from the straight-line winds, varying in severity depending on wind strength (e.g., “Expect considerable tree damage. Wind damage is also likely to mobile homes, roofs, and outbuildings.”). Since July 28, 2021 (or as late as August 2 in certain County Warning Areas), the NWS has incorporated categorical damage threat indicators for higher-end hail and/or wind events at the bottom of text products for severe thunderstorm warnings (including update statements to existing warnings issued as Severe Weather Statements): * Considerable – to be used when hail of or larger and/or winds at or above is indicated by radar or observed. * Destructive – to be used when hail of or larger and/or winds at or above is indicated by radar or observed. (Warnings assigned this indicator incorporate the notation "THIS IS A DESTRUCTIVE STORM FOR ..—which superseded the boilerplate "this is a particularly dangerous situation" wording—between the storm summary and hazard information in the product text to indicate certain areas under greatest threat from the specified wind speeds and/or hail size.) Similar to the indicators used for tornado warnings since the 2013 implementation of its Impact Based Warning system, the categorical criteria—which will be applicable to all NWS Weather Forecast Offices—was introduced to further explain to the public of the dangers of some thunderstorms, especially those that occur in the Great Plains, that can produce massive hailstones of baseball size () or larger that may fall fast enough to severely injure if not kill a person by repeated blunt trauma, and winds that can cause damage equivalent to hurricanes and tornadoes (especially to roofs and weaker structures such as outbuildings and mobile homes). When deemed necessary, initial warnings and Severe Weather Statement updates containing the "destructive" tag will be disseminated into the Wireless Emergency Alerts system as well.

Canada

In Canada, a severe thunderstorm is defined as having wind gusts of greater than , hail with a diameter of greater than , rainfall rates of greater than in one hour or greater than in three hours, or tornadoes. Environment and Climate Change Canada issues severe thunderstorm warnings through regional offices of the Meteorological Service of Canada based in

Vancouver Vancouver is a major city in Western Canada, located in the Lower Mainland region of British Columbia. As the List of cities in British Columbia, most populous city in the province, the 2021 Canadian census recorded 662,248 people in the cit ...

Edmonton Edmonton is the capital city of the Provinces and territories of Canada, Canadian province of Alberta. It is situated on the North Saskatchewan River and is the centre of the Edmonton Metropolitan Region, which is surrounded by Central Alberta ...

Winnipeg Winnipeg () is the capital and largest city of the Provinces and territories of Canada, Canadian province of Manitoba. It is centred on the confluence of the Red River of the North, Red and Assiniboine River, Assiniboine rivers. , Winnipeg h ...

Toronto Toronto ( , locally pronounced or ) is the List of the largest municipalities in Canada by population, most populous city in Canada. It is the capital city of the Provinces and territories of Canada, Canadian province of Ontario. With a p ...

Montreal Montreal is the List of towns in Quebec, largest city in the Provinces and territories of Canada, province of Quebec, the List of the largest municipalities in Canada by population, second-largest in Canada, and the List of North American cit ...

and Dartmouth for specified municipalities and

census subdivisions The census geographic units of Canada are the census subdivisions defined and used by Canada's federal government statistics bureau Statistics Canada to conduct the country's quinquennial census. These areas exist solely for the purposes of sta ...

, sometimes including areas adjacent to a particular warned thunderstorm that are not in the immediate approximate path but may experience severe weather from adjacent thunderstorms during the warning timeframe. Warnings are disseminated to the public through broadcast and online media outlets, and Weatheradio Canada; depending on storm severity and regional office discretion, the warning may require activation of the National Public Alerting System (Alert Ready) () and feeding provincial alerting systems (such as

Alberta Emergency Alert Alberta Emergency Alert (AEA) was a public warning system in Alberta. The system was implemented in October 2011, replacing the former Alberta Emergency Public Warning System (EPWS). Based on Common Alerting Protocol (CAP), alerts were dissemin ...

and SaskAlert) to distribute the alert to local broadcast media and cellular phones.

United Kingdom

In United Kingdom, a severe thunderstorm is defined as having hail in excess of and straight-line winds in excess of . The

Met Office The Met Office, until November 2000 officially the Meteorological Office, is the United Kingdom's national weather and climate service. It is an executive agency and trading fund of the Department for Science, Innovation and Technology and ...

issues de facto severe thunderstorm warnings through general-purpose weather warning products disseminated by the National Severe Weather Warning Service (classified as yellow, amber or red, depending on storm severity and proximity to the time of expected onset of storm impacts).

Australia

In Australia, a severe thunderstorm is defined as having damaging winds in excess of , large hail of or larger, heavy rainfall, and

flash flood A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice and snow. Flash f ...

ing. Severe thunderstorm warnings are issued by regional offices of the

Bureau of Meteorology The Bureau of Meteorology (BOM or BoM) is an executive agency of the Government of Australia, Australian Government that is responsible for providing Weather forecasting, weather forecasts and Meteorology, meteorological services to Australia a ...

(BOM) based in Melbourne Docklands,

Adelaide Adelaide ( , ; ) is the list of Australian capital cities, capital and most populous city of South Australia, as well as the list of cities in Australia by population, fifth-most populous city in Australia. The name "Adelaide" may refer to ei ...

, Darwin,

Perth Perth () is the list of Australian capital cities, capital city of Western Australia. It is the list of cities in Australia by population, fourth-most-populous city in Australia, with a population of over 2.3 million within Greater Perth . The ...

and

Brisbane Brisbane ( ; ) is the List of Australian capital cities, capital and largest city of the States and territories of Australia, state of Queensland and the list of cities in Australia by population, third-most populous city in Australia, with a ...

. BOM-issued severe thunderstorm warnings are outlined as either a broad-based warning, covering expected impacts within a weather reporting area, or as a detailed warning, when a thunderstorm is within weather-watch radar range and includes a map depicting any existing thunderstorms and the forecast direction of movement for up to 60 minutes.

New Zealand

In New Zealand, a severe thunderstorm is defined by the Meteorological Service of New Zealand (MetService) () as having large hail of , damaging winds of , rainfall rates of at least per hour and/or tornadoes producing winds above (rated F1 or stronger on the

Fujita Scale The Fujita scale (F-Scale; ), or Fujita–Pearson scale (FPP scale), is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation. The official Fujita scale category is determ ...

). MetService issues severe thunderstorm warnings to alert

region In geography, regions, otherwise referred to as areas, zones, lands or territories, are portions of the Earth's surface that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and ...

s expected to experience severe weather phenomena meeting regional criteria and utilize the Common Alerting Protocol (CAP) to generate the warning statement. The warning is then disseminated to the public through terrestrial television and radio stations, online media, mobile app and SMS messaging through Emergency Mobile Alert (EMA); if a tornado has been sighted or indicated by radar within the warned area during the severe thunderstorm warning's duration, civil defense sirens, if present, are usually activated within the region to be affected to inform people who are present outdoors of the approaching tornado threat.

Philippines

In the Philippines, a severe thunderstorm is defined by the

Philippine Atmospheric, Geophysical and Astronomical Services Administration The Philippine Atmospheric, Geophysical and Astronomical Services Administration (, abbreviated as PAGASA , which means "hope" as in the Tagalog word ''pag-asa'') is the National Meteorological and Hydrological Services (NMHS) agency of the P ...

(PAGASA) as having strong winds, large hail, torrential rainfall, tornadoes, flash flooding and/or

landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...

s. PAGASA, through its regional services divisions, issue thunderstorm advisories to alert

regions In geography, regions, otherwise referred to as areas, zones, lands or territories, are portions of the Earth's surface that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and ...

and/or

provinces A province is an administrative division within a country or state. The term derives from the ancient Roman , which was the major territorial and administrative unit of the Roman Empire's territorial possessions outside Italy. The term ''provi ...

expected to experience severe weather phenomena meeting regional criteria within a period of two hours. Warnings are disseminated to the public through terrestrial television and radio outlets, online media, and via SMS messages through the

National Disaster Risk Reduction and Management Council The National Disaster Risk Reduction and Management Council (NDRRMC), formerly known as the National Disaster Coordinating Council (NDCC) until August 2011, is a working group of various government, non-government, civil sector and private sect ...

's Emergency Cell Broadcast System.

Criteria in various countries

Examples of severe thunderstorm warnings

Here is an example of a Severe Thunderstorm Warning issued by the National Weather Service in San Angelo, Texas.

Severe Thunderstorm Warning
VAC059-153-600-683-685-140130-
/O.NEW.KLWX.SV.W.0529.190814T0058Z-190814T0130Z/
Severe Thunderstorm Warning
TXC151-253-042245-
/O.NEW.KSJT.SV.W.0017.220404T2223Z-220404T2245Zny

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service San Angelo TX
523 PM CDT Mon Apr 4 2022

The National Weather Service in San Angelo has issued a

* Severe Thunderstorm Warning for...
  Western Jones County in west central Texas...
  East central Fisher County in west central Texas...

* Until 545 PM CDT.

* At 521 PM CDT, a severe thunderstorm was located near Neinda,
  moving east at 40 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Hail damage to vehicles is expected. Expect wind damage
           to roofs, siding, and trees.

* This severe thunderstorm will be near...
  Neinda around 525 PM CDT.
  Anson around 540 PM CDT.

Other locations impacted by this severe thunderstorm include Truby
and The Intersection Of Us-180 And Ranch Road 126.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

To report severe weather, contact your nearest law enforcement
agency. They will send your report to the National Weather Service
office in San Angelo.

Large hail and damaging winds and continuous cloud to ground
lightning is occurring with this storm. Move indoors immediately.
Lightning is one of nature`s leading killers. Remember, if you can
hear thunder, you are close enough to be struck by lightning.

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 3261 10025 3276 10031 3294 9990 3263 9981
TIME...MOT...LOC 2221Z 258DEG 33KT 3271 10012

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

TP

This is a Severe Thunderstorm Warning issued for a cluster of severe thunderstorms.

Severe Thunderstorm Warning
ALC003-FLC033-113-130200-
/O.NEW.KMOB.SV.W.0225.200713T0114Z-200713T0200Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Mobile AL
814 PM CDT Sun Jul 12 2020

The National Weather Service in Mobile has issued a

* Severe Thunderstorm Warning for...
  Southeastern Baldwin County in southwestern Alabama...
  West central Santa Rosa County in northwestern Florida...
  Escambia County in northwestern Florida...

* Until 900 PM CDT.

* At 813 PM CDT, a cluster of severe thunderstorms was located near
  Bay Minette, moving southeast at 35 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect damage to roofs, siding, and trees.

* Locations impacted include...
  Ensley, Gonzalez, Bay Minette, Pace, Lillian, Molino and Perdido
  Beach.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Damaging winds and continuous cloud to ground lightning is occurring
with this storm. Move indoors immediately.
Lightning is one of nature's leading killers. Remember, if you can
hear thunder, you are close enough to be struck by lightning.

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 3022 8750 3092 8781 3099 8770 3070 8706
TIME...MOT...LOC 0113Z 301DEG 31KT 3084 8779

HAIL...<.75IN
WIND...60MPH

$$

CGAL

This is a Severe Thunderstorm Warning for winds associated with a strong

outflow boundary An outflow boundary, also known as a gust front, is a storm-scale or mesoscale meteorology, mesoscale boundary separating thunderstorm-cooled air (Outflow (meteorology), outflow) from the surrounding air; similar in effect to a cold front, with ...

, as opposed to a traditional thunderstorm.

287 
WUUS53 KLOT 162204
SVRLOT
ILC031-043-063-093-097-111-197-162245-
/O.NEW.KLOT.SV.W.0073.240616T2204Z-240616T2245Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Chicago/Romeoville
504 PM CDT Sun Jun 16 2024

The National Weather Service in Chicago has issued a

* Severe Thunderstorm Warning for...
  Southeastern Kendall County in northeastern Illinois...
  Lake County in northeastern Illinois...
  Will County in northeastern Illinois...
  Northeastern Grundy County in northeastern Illinois...
  Northeastern McHenry County in northeastern Illinois...
  DuPage County in northeastern Illinois...
  Cook County in northeastern Illinois...

* Until 545 PM CDT.

* At 502 PM CDT, severe outflow winds from thunderstorms were 
  located along a line extending from Channel Lake to Elk Grove 
  Village to near Romeoville to near Morris, moving east at 35 mph. 
  This strong surge of outflow winds from weakening thunderstorms 
  will produce wind gusts of 50 to locally 60 mph, strong enough to 
  down some trees and powerlines. These strong winds will be 
  accompanied by little or no rain.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Expect damage to roofs, siding, and trees.

* Severe thunderstorms will be near...
  Chicago, Joliet, Waukegan, Arlington Heights, Bolingbrook, Des 
  Plaines, Mount Prospect, Downers Grove, Glenview, and Elmhurst 
  around 510 PM CDT.
  Skokie, Orland Park, Berwyn, Oak Park, Austin, Highland Park, 
  Wilmette, Zion, Brookfield, and Justice around 515 PM CDT.
  Cicero, Evanston, Oak Lawn, Irving Park, West Ridge, Burbank, 
  Mokena, Palos Hills, Logan Square, and Humboldt Park around 520 PM 
  CDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Wind damage with these storms will occur before any rain or
lightning. Do not wait for the sound of thunder before taking cover.
SEEK SHELTER IMMEDIATELY inside a sturdy structure and stay away from
windows.

&&

LAT...LON 4249 8780 4227 8783 4213 8774 4206 8767
      4190 8761 4190 8760 4188 8762 4185 8761
      4178 8756 4173 8757 4129 8793 4129 8801
      4128 8802 4128 8847 4160 8822 4199 8809
      4250 8825
TIME...MOT...LOC 2202Z 258DEG 32KT 4247 8815 4201 8801 4162 8813 4136
8833

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...<.75 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Izzi

This is a Severe Thunderstorm Warning with a "considerable" tag to denote that 70 mph wind gusts were possible. � 664 WUUS53 KLBF 052239 SVRLBF NEC017-031-052300- /O.NEW.KLBF.SV.W.0108.210805T2239Z-210805T2300Z/ BULLETIN - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Warning National Weather Service North Platte NE 539 PM CDT Thu Aug 5 2021 The National Weather Service in North Platte has issued a * Severe Thunderstorm Warning for... East central Cherry County in north central Nebraska... Southwestern Brown County in north central Nebraska... * Until 600 PM CDT. * At 539 PM CDT, a severe thunderstorm was located 12 miles southwest of Johnstown, or 18 miles southwest of Ainsworth, moving southeast at 30 mph. HAZARD...70 mph wind gusts and quarter size hail. SOURCE...Radar indicated. IMPACT...Hail damage to vehicles is expected. Expect considerable tree damage. Wind damage is also likely to mobile homes, roofs, and outbuildings. * Locations impacted include... Moon Lake, Willow Lake State Wildlife Management Area and Long Lake State Wildlife Management Area. PRECAUTIONARY/PREPAREDNESS ACTIONS... For your protection move to an interior room on the lowest floor of a building. && LAT...LON 4244 10033 4249 10019 4227 9991 4219 10022 TIME...MOT...LOC 2239Z 327DEG 26KT 4242 10018 THUNDERSTORM DAMAGE THREAT...CONSIDERABLE HAIL THREAT...RADAR INDICATED MAX HAIL SIZE...1.00 IN WIND THREAT...RADAR INDICATED MAX WIND GUST...70 MPH $$ Sporer This is a Severe Thunderstorm Warning with "destructive" wording to denote that three-inch hail was possible with this storm, with a request for activation of Wireless Emergency Alerts (as indicated by the wording "BULLETIN - EAS ACTIVATION REQUESTED" at the top of the warning). � 115 WUUS53 KLBF 052249 SVRLBF NEC089-149-052330- /O.NEW.KLBF.SV.W.0109.210805T2249Z-210805T2330Z/ BULLETIN - EAS ACTIVATION REQUESTED Severe Thunderstorm Warning National Weather Service North Platte NE 549 PM CDT Thu Aug 5 2021 The National Weather Service in North Platte has issued a * Severe Thunderstorm Warning for... Northeastern Rock County in north central Nebraska... Southwestern Holt County in north central Nebraska... * Until 630 PM CDT. * At 548 PM CDT, a severe thunderstorm was located near Newport, or 15 miles east of Bassett, moving southeast at 40 mph. THIS IS A DESTRUCTIVE STORM APPROACHING STUART! HAZARD...Three inch hail and 70 mph wind gusts. SOURCE...Radar indicated. IMPACT...People and animals outdoors will be severely injured. Expect shattered windows, extensive damage to roofs, siding, and vehicles. * Locations impacted include... O'neill, O'Neill, Atkinson, Stuart, Newport and Emmet. This includes the following highways... Highway 20 between mile markers 265 and 308. Highway 281 between mile markers 183 and 189. PRECAUTIONARY/PREPAREDNESS ACTIONS... For your protection move to an interior room on the lowest floor of a building. Prepare immediately for large hail and damaging winds. People outside should move immediately to shelter inside a strong building. Stay away from windows. This is a dangerous storm. Prepare immediately for large destructive hail capable of producing significant damage. People outside should move to shelter inside a strong building, and stay away from windows. && LAT...LON 4256 9946 4274 9928 4252 9857 4224 9884 TIME...MOT...LOC 2248Z 300DEG 33KT 4262 9924 THUNDERSTORM DAMAGE THREAT...DESTRUCTIVE HAIL THREAT...RADAR INDICATED MAX HAIL SIZE...3.00 IN WIND THREAT...RADAR INDICATED MAX WIND GUST...70 MPH $$ Sporer On August 16, 2019 at 1:31 a.m. MDT, the National Weather Service in

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incorporated the "emergency" wording into a Severe Thunderstorm Warning. In this instance, the "severe thunderstorm emergency" statement was included to denote that diameter hail (as confirmed by storm spotter reports) was imminent in portions of Scotts Bluff,

Banner A banner can be a flag or another piece of cloth bearing a symbol, logo, slogan or another message. A flag whose design is the same as the shield in a coat of arms (but usually in a square or rectangular shape) is called a banner of arms. Also, ...

and

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Counties in

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, specifically areas around the towns of Scottsbluff and Gering.

�
187 
WWUS55 KCYS 160731
SVSCYS

Severe Weather Statement
National Weather Service Cheyenne WY
131 AM MDT Fri Aug 16 2019

NEC007-157-165-160815-
/O.CON.KCYS.SV.W.0342.000000T0000Z-190816T0815Z/
Scotts Bluff NE-Banner NE-Sioux NE-
131 AM MDT Fri Aug 16 2019

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 215 AM MDT
FOR SCOTTS BLUFF...NORTHEASTERN BANNER AND SOUTHEASTERN SIOUX
COUNTIES...

...THIS IS A SEVERE THUNDERSTORM EMERGENCY FOR SCOTTSBLUFF AND 
GERING!...

At 129 AM MDT, a severe thunderstorm was located near Scotts Bluff 
National Monument, or near Scottsbluff, moving east at 40 mph. 3 
INCH DIAMETER HAIL IS IMMINENT! PREPARE NOW FOR DESTRUCTIVE HAIL!

This is a very dangerous storm!

HAZARD...Three inch hail and 60 mph wind gusts.

SOURCE...Trained weather spotters.

IMPACT...People and animals outdoors will be severely injured. 
         Expect shattered windows, extensive damage to roofs, 
         siding, and vehicles.

Locations impacted include...
Scottsbluff, Gering, Mitchell, Terrytown, Minatare, Wildcat Hills
State Recreation Area, Lake Minatare Campground, Wildcat Hills
Campground, Scotts Bluff National Monument, Hubbard Hill, Scottsbluff
Airport, Lake Minatare, Lake Alice, Melbeta and McGrew.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

This is a dangerous storm. Prepare immediately for large destructive
hail capable of producing significant damage. People outside should
move to a shelter, inside a strong building and away from windows.

&&

LAT...LON 4185 10394 4233 10379 4230 10344 4209 10345
      4209 10340 4200 10340 4198 10336 4156 10337
      4170 10388
TIME...MOT...LOC 0729Z 288DEG 34KT 4189 10374

HAIL...3.00IN
WIND...60MPH
 
$$

Lyons

References

External links

Bureau of Meteorology: Severe Thunderstorm Warnings

Meteorological Service of Canada

United States National Weather Service
{{SevWea nav Weather warnings and advisories