Flash flood watch
A flash flood watch (SAME code: FFA; also referred as a "green box" by meteorologists) is issued by the National Weather Service 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 Flash Flood Watch
Below is an example issued by the National Weather Service in Cleveland, Ohio.
421 WGUS61 KCLE 230740 FFACLE URGENT - IMMEDIATE BROADCAST REQUESTED FLOOD WATCH NATIONAL WEATHER SERVICE CLEVELAND OH 340 AM EDT SAT JUL 23 2011 OHZ003-006>013-017>023-027>033-036>038-047-231545- /O.NEW.KCLE.FF.A.0002.110723T0800Z-110724T1000Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ LUCAS-WOOD-OTTAWA-SANDUSKY-ERIE OH-LORAIN-CUYAHOGA-LAKE-GEAUGA- HANCOCK-SENECA-HURON-MEDINA-SUMMIT-PORTAGE-TRUMBULL-WYANDOT- CRAWFORD-RICHLAND-ASHLAND-WAYNE-STARK-MAHONING-MARION-MORROW- HOLMES-KNOX- INCLUDING THE CITIES OF...TOLEDO...BOWLING GREEN...PORT CLINTON... FREMONT...SANDUSKY...LORAIN...CLEVELAND...MENTOR...CHARDON... FINDLAY...TIFFIN...NORWALK...MEDINA...AKRON...RAVENNA...WARREN... UPPER SANDUSKY...CAREY...BUCYRUS...MANSFIELD...ASHLAND... WOOSTER...CANTON...YOUNGSTOWN...MARION...MOUNT GILEAD... MILLERSBURG...MOUNT VERNON 340 AM EDT SAT JUL 23 2011 ...FLASH FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT... THE NATIONAL WEATHER SERVICE IN CLEVELAND HAS ISSUED A * FLASH FLOOD WATCH FOR PORTIONS OF NORTH CENTRAL OHIO... NORTHEAST OHIO AND NORTHWEST OHIO...INCLUDING THE FOLLOWING AREAS...IN NORTH CENTRAL OHIO...ASHLAND...CRAWFORD...ERIE OH... HURON...KNOX...LORAIN...MARION...MORROW AND RICHLAND. IN NORTHEAST OHIO...CUYAHOGA...GEAUGA...HOLMES...LAKE... MAHONING...MEDINA...PORTAGE...STARK...SUMMIT...TRUMBULL AND WAYNE. IN NORTHWEST OHIO...HANCOCK...LUCAS...OTTAWA... SANDUSKY...SENECA...WOOD AND WYANDOT. * THROUGH LATE TONIGHT * SHOWERS AND THUNDERSTORMS ARE LIKELY TODAY AND SOME OF THE THUNDERSTORMS WILL HAVE HEAVY RAIN. RECENT RAINS HAVE MADE THE GROUND WET...AND ANY ADDITIONAL HEAVY RAIN WILL BRING THE POTENTIAL FOR FLOODING. * THERE IS ALSO A CHANCE FOR REPEAT THUNDERSTORMS TODAY AND TONIGHT. AREAS THAT GET MULTIPLE THUNDERSTORMS WILL BE AT RISK FOR FLOODING. PRECAUTIONARY/PREPAREDNESS ACTIONS... A FLASH FLOOD WATCH MEANS THE THREAT OF FLASH FLOODING EXISTS ALONG RIVERS AND CREEKS AND LOW LYING AREAS. IF YOU ARE IN THE WATCH AREA YOU SHOULD MONITOR WEATHER CONDITIONS CLOSELY. BE READY TO MOVE TO HIGHER GROUND IF FLOODING IS OBSERVED OR A WARNING IS ISSUED. STAY TUNED TO WEATHER RADIO FOR FURTHER UPDATES. && $$
PDS watches
In the event that a flash flood watch is likely to lead to a major flash flood disaster, 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
References
- "Flash flood watch definition". Weather.gov. 16 August 2019.
- "Flood Warning Services". Bureau of Meteorology. Retrieved 19 June 2014.
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