Flash flood watch

A flash flood watch (SAME code: FFA; also referred as a "green box" by meteorologists) is severe weather watch product of the National Weather Service that is issued when conditions are favorable for flash flooding in flood-prone areas, usually when grounds are already saturated from recent rains, or when upcoming rains will have the potential to cause a flash flood. These watches are also occasionally issued when a dam may break in the near future.[1]

Countries such as Australia also issue similarly worded warnings.[2]

Example of a flash flood watch

[edit]

Below is an example issued by the National Weather Service in Mount Holly, New Jersey.

  688 WGUS61 KPHI 071932 FFAPHI  URGENT - IMMEDIATE BROADCAST REQUESTED Flood Watch National Weather Service Mount Holly NJ 332 PM EDT Wed Jul 7 2021  NJZ001-007-PAZ054-055-060>062-080745- /O.NEW.KPHI.FF.A.0003.210708T1600Z-210709T1600Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Sussex-Warren-Carbon-Monroe-Berks-Lehigh-Northampton- Including the cities of Jim Thorpe, Allentown, Newton, Washington, Bethlehem, Stroudsburg, Reading, and Easton 332 PM EDT Wed Jul 7 2021  ...FLASH FLOOD WATCH IN EFFECT FROM THURSDAY AFTERNOON THROUGH FRIDAY MORNING...  The National Weather Service in Mount Holly has issued a  * Flash Flood Watch for portions of northern New Jersey...and   Pennsylvania...including the following areas...in northern New   Jersey...Sussex and Warren. In Pennsylvania...Berks, Carbon,   Lehigh, Monroe, and Northampton.  * From Thursday afternoon through Friday morning.  * Heavy rainfall will develop over portions of eastern PA and NW New   Jersey ahead of Tropical Storm Elsa Thursday afternoon. The heavy   rains will see 1 to 2 inches with locally higher amounts and then   will see another 1 to 2 inches with the heavy rainfall associated   with Tropical Storm Elsa Thursday evening through the overnight   hours.  * Heavy rain in short periods of time will cause the potential for   streams and creeks to quickly rise out of their banks as well as   the potential for flash flooding in areas of poor drainage.  $$  DEZ001>004-MDZ012-015-019-020-NJZ008>010-012>027-PAZ070-071-101>106- 080745- /O.NEW.KPHI.FF.A.0003.210708T2100Z-210709T1600Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ New Castle-Kent-Inland Sussex-Delaware Beaches-Kent MD-Queen Annes- Talbot-Caroline-Morris-Hunterdon-Somerset-Middlesex-Western Monmouth- Eastern Monmouth-Mercer-Salem-Gloucester-Camden-Northwestern Burlington-Ocean-Cumberland-Atlantic-Cape May-Atlantic Coastal Cape May-Coastal Atlantic-Coastal Ocean-Southeastern Burlington-Delaware- Philadelphia-Western Chester-Eastern Chester-Western Montgomery- Eastern Montgomery-Upper Bucks-Lower Bucks- Including the cities of Glassboro, Denton, Jackson, Flemington, Media, Philadelphia, Doylestown, Chalfont, Morristown, Pennsville, Honey Brook, Centreville, Norristown, Georgetown, Mount Holly, Ocean City, Cherry Hill, Moorestown, Freehold, Pottstown, Hammonton, Cape May Court House, Oxford, Kennett Square, Sandy Hook, Chestertown, Morrisville, West Chester, Millville, Wilmington, New Brunswick, Dover, Trenton, Lansdale, Wharton State Forest, Atlantic City, Collegeville, Long Beach Island, Camden, Easton, Perkasie, Rehoboth Beach, and Somerville 332 PM EDT Wed Jul 7 2021  ...FLASH FLOOD WATCH IN EFFECT FROM THURSDAY AFTERNOON THROUGH FRIDAY MORNING...  The National Weather Service in Mount Holly has issued a  * Flash Flood Watch for portions of Delaware...northeast Maryland...   New Jersey...and southeast Pennsylvania...including the following   areas...in Delaware...Delaware Beaches, Inland Sussex, Kent, and   New Castle. In northeast Maryland...Caroline, Kent MD, Queen   Annes, and Talbot. In New Jersey...Atlantic, Atlantic Coastal Cape   May, Camden, Cape May, Coastal Atlantic, Coastal Ocean,   Cumberland, Eastern Monmouth, Gloucester, Hunterdon, Mercer,   Middlesex, Morris, Northwestern Burlington, Ocean, Salem,   Somerset, Southeastern Burlington, and Western Monmouth. In   southeast Pennsylvania...Delaware, Eastern Chester, Eastern   Montgomery, Lower Bucks, Philadelphia, Upper Bucks, Western   Chester, and Western Montgomery.  * From Thursday afternoon through Friday morning.  * Tropical Storm Elsa will move across portions of DelMarVa, New   Jersey, and eastern PA Thursday night, bringing heavy rainfall to   the region. Expected rainfall totals across DelMarVa and New   Jersey range from 2 to 3 inches, with locally higher amounts up to   5 inches possible. Further west of the I-95 corridor could expect   to see 1-2 inches, with locally higher amounts to 3 inches   possible.  * Heavy rain in short periods of time will cause the potential for   streams and creeks to quickly rise out of their banks as well as   the potential for flash flooding in urban areas.  $$  Deal  

Source:[3]

PDS watches

[edit]

If a flash flood watch is likely to lead to a major flash flood disaster, then enhanced wording with the words This is a particularly dangerous situation (PDS) can be added to the watch; this is occasionally issued. Below is an example issued by the National Weather Service in Memphis, Tennessee.

URGENT - IMMEDIATE BROADCAST REQUESTED  FLOOD WATCH  NATIONAL WEATHER SERVICE MEMPHIS TN  239 PM CDT SUN APR 24 2011    ...VERY HEAVY RAINFALL THROUGH THE MIDDLE OF THIS WEEK WILL LIKELY  LEAD TO SIGNIFICANT...WIDESPREAD FLASH FLOODING...    ...THIS IS A PARTICULARLY DANGEROUS SITUATION...    A BOUNDARY WILL CONTINUE TO REMAIN STATIONARY ACROSS SOUTHERN  MISSOURI INTO KENTUCKY THROUGH MONDAY. REPEATED ROUNDS OF  THUNDERSTORMS WILL TRACK ALONG THE FRONT BRINGING HEAVY RAINFALL.  THEN A LOW PRESSURE SYSTEM WILL TRACK ALONG IT INTO MISSOURI AND  PUSH THE FRONT FURTHER SOUTH TO ALONG THE I-40 CORRIDOR MONDAY  NIGHT THROUGH TUESDAY NIGHT. THIS WILL SHIFT THE HEAVY RAIN AXIS  FURTHER SOUTH TO ALONG AND JUST NORTH OF THE I-40 CORRIDOR.    A SECOND LOW PRESSURE SYSTEM WILL TRACK ALONG THE NEWLY STALLED  BOUNDARY AND SET OFF ADDITIONAL TRAINING THUNDERSTORMS LATE  TUESDAY NIGHT AND WEDNESDAY. THE FINAL COLD FRONT WILL PASS  THROUGH LATE WEDNESDAY AFTERNOON...ENDING THE PERSISTENT HEAVY  RAINFALL.    ARZ026>028-035-036-048-049-058-MSZ001>014-TNZ003-004-019>021-  048>055-088>092-250400-  /O.NEW.KMEG.FF.A.0007.110426T0000Z-110428T0000Z/  /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/  CRAIGHEAD-POINSETT-MISSISSIPPI-CROSS-   CRITTENDEN-ST. FRANCIS-  LEE AR-PHILLIPS-DESOTO-MARSHALL-BENTON MS-TIPPAH-ALCORN-  TISHOMINGO-TUNICA-TATE-PRENTISS-   COAHOMA-QUITMAN-PANOLA-LAFAYETTE-     UNION-WEAKLEY-HENRY-DYER-GIBSON-CARROLL-LAUDERDALE-TIPTON-HAYWOOD-  CROCKETT-MADISON-CHESTER-HENDERSON-   DECATUR-SHELBY-FAYETTE-  HARDEMAN-MCNAIRY-HARDIN-  INCLUDING THE CITIES OF...JONESBORO...HARRISBURG...BLYTHEVILLE...  WYNNE...WEST MEMPHIS...FORREST CITY...HELENA...   SOUTHAVEN...  OLIVE BRANCH...CORINTH...IUKA...TUNICA...[[Booneville,   Mississippi|BOONEVILLE]]...  CLARKSDALE...BATESVILLE...OXFORD...NEW ALBANY...   MARTIN...  DRESDEN...PARIS...DYERSBURG...HUMBOLDT...MILAN...HUNTINGDON...  COVINGTON...JACKSON...LEXINGTON...BARTLETT...GERMANTOWN...  COLLIERVILLE...MEMPHIS...MILLINGTON...SOMERVILLE...   BOLIVAR...  SAVANNAH  239 PM CDT SUN APR 24 2011    ...FLASH FLOOD WATCH IN EFFECT FROM MONDAY EVENING THROUGH  WEDNESDAY EVENING...    THE NATIONAL WEATHER SERVICE IN MEMPHIS HAS ISSUED A    * FLASH FLOOD WATCH FOR PORTIONS OF EAST ARKANSAS...NORTH MISSISSIPPI  AND WEST TENNESSEE...INCLUDING THE FOLLOWING AREAS...IN EAST  ARKANSAS...CRAIGHEAD...CRITTENDEN...CROSS...  LEE...MISSISSIPPI...PHILLIPS...POINSETT AND ST. FRANCIS. IN  NORTH MISSISSIPPI...ALCORN...BENTON...COAHOMA...DESOTO...  LAFAYETTE...MARSHALL...PANOLA...PRENTISS...QUITMAN...TATE...  TIPPAH...TISHOMINGO...TUNICA AND UNION. IN WEST TENNESSEE...  CARROLL...CHESTER...CROCKETT...DECATUR...DYER...FAYETTE...  GIBSON...HARDEMAN...HARDIN...HAYWOOD...HENDERSON...HENRY...  LAUDERDALE...MADISON...MCNAIRY...SHELBY...TIPTON AND WEAKLEY.    * FROM MONDAY EVENING THROUGH WEDNESDAY EVENING.  * THIS IS A PARTICULARLY DANGEROUS SITUATION  * TOTAL RAINFALL AMOUNTS OF 5 TO 8 INCHES ARE EXPECTED ALONG AND  NORTH OF I-40 WITH 2 TO 5 INCHES EXPECTED SOUTH OF I-40. LOCALLY  HIGHER AMOUNTS ARE LIKELY.    * RAINFALL AMOUNTS SUCH AS THESE MAY LEAD TO WIDESPREAD...  SIGNIFICANT...AND LIFE THREATENING FLASH FLOODING. THIS EVENT  MAY BE AS SEVERE AS THE MAY 1–2, 2010 FLOODING IN PLACES. FLASH  FLOODING OF CITIES...RURAL AREAS...RIVERS...AND SMALL STREAMS  ARE POSSIBLE.    PRECAUTIONARY/PREPAREDNESS ACTIONS...    A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD  TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.    YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION  SHOULD FLASH FLOOD WARNINGS BE ISSUED.    &&    $$    ARZ008-009-017-018-MOZ113-115-TNZ001-002-250400-  /O.EXT.KMEG.FF.A.0006.000000T0000Z-110428T0000Z/  /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/  RANDOLPH-CLAY-LAWRENCE-GREENE-DUNKLIN-PEMISCOT-LAKE-OBION-  INCLUDING THE CITIES OF...WALNUT RIDGE...PARAGOULD...KENNETT...  CARUTHERSVILLE...UNION CITY  239 PM CDT SUN APR 24 2011    ...FLASH FLOOD WATCH NOW IN EFFECT THROUGH WEDNESDAY EVENING...    THE FLASH FLOOD WATCH IS NOW IN EFFECT FOR    * PORTIONS OF EAST ARKANSAS...SOUTHEAST MISSOURI AND WEST  TENNESSEE...INCLUDING THE FOLLOWING AREAS...IN EAST ARKANSAS...  CLAY...GREENE...LAWRENCE AND RANDOLPH. IN SOUTHEAST MISSOURI...  DUNKLIN AND PEMISCOT. IN WEST TENNESSEE...LAKE AND OBION.    * THROUGH WEDNESDAY EVENING.  * THIS IS A PARTICULARLY DANGEROUS SITUATION  * ADDITIONAL RAINFALL AMOUNTS OF 6 TO 9 INCHES ARE EXPECTED.  LOCALLY HIGHER AMOUNTS ARE LIKELY. THIS...IN COMBINATION OF  THE 2 TO 4 INCHES THAT HAVE ALREADY FALLEN MAY LEAD TO TOTAL  RAINFALL AMOUNTS IN EXCESS OF 12 INCHES IN MANY LOCATIONS.    * RAINFALL AMOUNTS SUCH AS THESE WILL LIKELY LEAD TO WIDESPREAD...  SIGNIFICANT...AND LIFE THREATENING FLASH FLOODING. THIS EVENT  MAY BE AS SEVERE AS THE MAY 1-2 2010 FLOODING IN MANY PLACES.  FLASH FLOODING OF CITIES...RURAL AREAS...RIVERS...AND SMALL  STREAMS ARE POSSIBLE.    PRECAUTIONARY/PREPAREDNESS ACTIONS...    A FLASH FLOOD WATCH MEANS THAT CONDITIONS MAY DEVELOP THAT LEAD  TO FLASH FLOODING. FLASH FLOODING IS A VERY DANGEROUS SITUATION.    YOU SHOULD MONITOR LATER FORECASTS AND BE PREPARED TO TAKE ACTION  SHOULD FLASH FLOOD WARNINGS BE ISSUED.    &&    $$    BORGHOFF  

See also

[edit]

References

[edit]
  1. ^ "Flash flood watch definition". Weather.gov. 16 August 2019.
  2. ^ "Flood Warning Services". Bureau of Meteorology. Retrieved 19 June 2014.
  3. ^ "IEM::Valid Time Event Code". Iowa State University. Iowa Environmental Mesonet. Retrieved 15 December 2021.