Flash flood warning

A Flash Flood Warning (SAME code: FFW) is issued by the United States National Weather Service when a flash flood is imminent or occurring in the warned area. A flash flood is a sudden, violent flood after a heavy rain, or occasionally after a dam break. Rainfall intensity and duration, topography, soil conditions, and ground cover contribute to flash flooding.

Most flash floods occur when there is a heavy amount of precipitation falling in an area and that water is then channeled through streams or narrow gullies. Flash floods may take minutes or hours to develop. It is possible to experience a flash flood without witnessing any rain. In this case, there would be heavy rain in areas upstream of the warned location.[1]

Flash flood alerts

There are two types of alerts for flash floods which are issued by the National Weather Service. One is a flash flood watch, which means that conditions are favorable for flash flooding, and the other is a flash flood warning, meaning that a flash flood is occurring or one will occur imminently and is usually issued when there are strong weather radar echoes for an area that is prone to flash flooding.[2] Flash floods can also occur because of a dam or levee failure,[3] or because of a sudden release of water held by an ice jam.

Residents are usually urged to do the following when flash flooding is imminent:[4]

  • Be aware of any signs of heavy rain
  • Move to higher ground if rapidly rising water is seen or heard
  • Not attempt to cross the flowing water

In addition, some NWS Weather Forecast Offices have instituted an enhanced flash flood warning, referred to as a flash flood emergency (or as termed by the Albany, New York office as a flash flood warning emergency[5]), which indicates a severe flooding situation in densely populated areas, similar to the procedure for declaring a tornado emergency.

On August 27, 2017, as Hurricane Harvey brought torrential rain to southeast Texas, the NWS issued a "Flash Flood Emergency for Catastrophic Life Threatening Flooding."[6]

On September 10, 2017, the NWS issued a Flash Flood Emergency for life-threatening storm surge because of Hurricane Irma in southwestern Florida at the eye landfall. [7] [8]

Example of a flash flood warning and emergency

Warning

This warning was issued following a dam failure along the Minnesota-Wisconsin border.

Flash Flood Warning
MNC115-WIC013-031-192330-
/O.NEW.KDLH.FF.W.0012.180618T2329Z-180619T2330Z/
/00000.U.DM.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Duluth MN
629 PM CDT MON JUN 18 2018

The National Weather Service in Duluth MN has issued a

* Flash Flood Warning for...
  A Dam Failure in...
  East central Pine County in east central Minnesota...
  Southwestern Douglas County in northwestern Wisconsin...
  North central Burnett County in northwestern Wisconsin...

* Until 630 PM CDT Tuesday

* At 629 PM CDT, local law enforcement reported the Radigan Flowage
  Dam west of Dairyland has failed, causing flash flooding
  downstream on the Tamarack River south of the Dam as it flows
  towards the Saint Croix River.

* Locations impacted include...
  Town Rd T west of Dairyland.
  Swedish Highway at the Tamarack River.
  Highway T west of Cozy Corner.
  Markville Road east of Markville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don`t drown when encountering flooded roads. Most flood
deaths occur in vehicles.

Move to higher ground now. Act quickly to protect your life.

Please report flooding to your local law enforcement agency when you
can do so safely.

&&

LAT...LON 4623 9218 4616 9226 4611 9228 4607 9229
      4605 9234 4612 9234 4617 9230 4622 9225

$$

LE

Emergency

Flash Flood Emergency In Initial Bulletin

FLASH FLOOD WARNING
KSC091-209-MOC047-095-270645-
/O.NEW.KEAX.FF.W.0043.160827T0247Z-160827T0645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
947 PM CDT FRI AUG 26 2016

...FLASH FLOOD EMERGENCY FOR THE IMMEDIATE DOWNTOWN KANSAS CITY
AREA!...

THE NATIONAL WEATHER SERVICE IN PLEASANT HILL HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  EASTERN WYANDOTTE COUNTY IN NORTHEASTERN KANSAS...
  NORTHEASTERN JOHNSON COUNTY IN EAST CENTRAL KANSAS...
  NORTHWESTERN JACKSON COUNTY IN WEST CENTRAL MISSOURI...
  SOUTHWESTERN CLAY COUNTY IN WEST CENTRAL MISSOURI...

* UNTIL 145 AM CDT

* AT 943 PM CDT...DOPPLER RADAR INDICATED HEAVY RAIN ACROSS THE
  WARNED AREA. LIFE THREATENING FLASH FLOODING IS ALREADY OCCURRING!

  THIS IS A FLASH FLOOD EMERGENCY FOR THE KANSAS CITY
METRO...PARTICULARLY THE DOWNTOWN KANSAS CITY AREA! THIS IS  A
PARTICULARLY DANGEROUS SITUATION. SEEK HIGHER GROUND NOW!

* SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...
  KANSAS CITY...OVERLAND PARK...INDEPENDENCE...SHAWNEE...LENEXA...
  LEAWOOD...RAYTOWN...LIBERTY...GLADSTONE...PRAIRIE VILLAGE...
  MERRIAM...MISSION...EDWARDSVILLE...NORTH KANSAS CITY...FAIRWAY...
  MISSION HILLS...SUGAR CREEK...RIVERSIDE...WESTWOOD AND CLAYCOMO.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MOVE TO HIGHER GROUND NOW. THIS IS AN EXTREMELY DANGEROUS AND
LIFE-THREATENING SITUATION. DO NOT ATTEMPT TO TRAVEL UNLESS YOU ARE
FLEEING AN AREA SUBJECT TO FLOODING OR UNDER AN EVACUATION ORDER.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGERS OF FLOODING.

A FLASH FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR OCCURRING.
IF YOU ARE IN THE WARNED AREA MOVE TO HIGHER GROUND IMMEDIATELY.
RESIDENTS LIVING ALONG STREAMS AND CREEKS SHOULD TAKE IMMEDIATE
PRECAUTIONS TO PROTECT LIFE AND PROPERTY.

&&

LAT...LON 3917 9466 3915 9466 3916 9460 3919 9460
      3927 9435 3907 9428 3892 9477 3912 9481

$$

GITRO

Flash Flood Emergency In Follow-Up Statement

This particular Flash Flood Emergency also includes the enhanced wording "Particularly Dangerous Situation".

Flash Flood Statement
National Weather Service Chicago/Romeoville Il
827 PM CDT MON JUN 18 2018

ILC007-201-190515-
/O.CON.KLOT.FF.W.0005.000000T0000Z-180619T0515Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Winnebago IL-Boone IL-
827 PM CDT MON JUN 18 2018

...THIS IS A FLASH FLOOD EMERGENCY FOR THE CITY OF ROCKFORD...

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1215 AM CDT FOR
WINNEBAGO AND BOONE COUNTIES...

At 821 PM CDT, Doppler radar indicated heavy rain across the warned
area.  Flash flooding is ongoing and could become worse as heavy
rainfall continues to fall over the area this evening. There have
been numerous reports of people stranded in their cars as well as
reports of flooding in Mercy Hospital leading to evacuations. With
rainfall amounts of over 3 inches already fallen and additional
rainfall amounts expected through the evening conditions are not
likely to improve quickly.

This is a FLASH FLOOD EMERGENCY for The city of Rockford. This is a
PARTICULARLY DANGEROUS SITUATION. SEEK HIGHER GROUND NOW!

Some locations that will experience flooding include...
Rockford, Belvidere, Loves Park, Machesney Park, Rockford Airport,
Roscoe, Poplar Grove, Cherry Valley, Winnebago, Pecatonica, Capron,
Timberlane, Caledonia and New Millford.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move to higher ground now. This is an extremely dangerous and
life-threatening situation. Do not attempt to travel unless you are
fleeing an area subject to flooding or under an evacuation order.

Turn around, don`t drown when encountering flooded roads. Most flood
deaths occur in vehicles.

&&

LAT...LON 4241 8871 4216 8871 4215 8916 4221 8917
      4220 8940 4241 8939

$$

BIRK

See also

Severe weather terminology (United States)

References

  1. ↑ "NOAA".
  2. ↑ "Stormwarn.com".
  3. ↑ "New Orleans Levee Breach Flash Flood Warning".
  4. ↑ "NOAAWatch Home". Archived from the original on 23 January 2014. Retrieved 17 January 2014.
  5. ↑ NWGeek on YouTube. "NWS Albany Flash Flood Warning Emergency EAS - Newfane, VT". NWRGeek. NWRGeek Productions. Retrieved 1 August 2012.
  6. ↑ "IEM Valid Time Extent Code (VTEC) App". Mesonet.agron.iastate.edu. Retrieved 2017-08-27.
  7. ↑ https://web.archive.org/web/20170910195340/http://forecast.weather.gov/showsigwx.php?warnzone=FLZ069&warncounty=FLC021&firewxzone=FLZ069&local_place1=Marco%20FL&product1=Flash+Flood+Warning&lat=25.9541&lon=-81.7246
  8. ↑ http://mesonet.agron.iastate.edu/vtec/#2017-O-NEW-KMFL-FF-W-0007/USCOMP-N0Q-201709101915
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