Flash flood watch
 | This article contains too many or overly lengthy quotations. (December 2019) |
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 and may precede a flash flood warning, usually when grounds are already saturated by water from recent rains, and/or when heavy upcoming rains will have the potential to cause a flash flood. These watches are also occasionally issued when a nearby vulnerable dam may break in the near future.[1]
Countries such as Australia also issue similarly worded weather watches.[2]
Example Flash Flood Watch
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
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
- Tornado warning
- Tornado watch
- Severe thunderstorm warning
- Severe thunderstorm watch
- Flash flood warning
- Particularly dangerous situation
References
- ^ "Flash flood watch definition". Weather.gov. 16 August 2019.
- ^ "Flood Warning Services". Bureau of Meteorology. Retrieved 19 June 2014.
- ^ "IEM::Valid Time Event Code". Iowa State University. Iowa Environmental Mesonet. Retrieved 15 December 2021.