Alert archive / New Jersey / Flash Flood Watches in 2021
Flash Flood Watch 4, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this flash flood watch at Jul 11, 2021, 3:45 PM EDT for 11 counties in New Jersey; 10 counties in Pennsylvania. It took effect at Jul 12, 2021, 11:23 AM EDT. It was in force for 16 hr.
The area
The counties it named.
The facts
- Issued
- Jul 11, 2021, 3:45 PM EDT (19:45 UTC)
- In effect from
- Jul 12, 2021, 11:23 AM EDT
- Expired
- Jul 13, 2021, 3:41 AM EDT
- In force
- 16 hr
- Issued by
- NWS Philadelphia/Mount Holly
- Flood severity
- None
All 21 counties
Burlington County, NJ, Camden County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Morris County, NJ, Somerset County, NJ, Sussex County, NJ, Warren County, NJ, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Delaware County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Philadelphia County, PA
The radar
The Philadelphia radar (KDIX), 76 km from the middle of the area, began a volume at 19:46 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The nearest sounding before it
Brookhaven, NY (KOKX), launched 12:00Z, 7.8 hours before the alert went out and 193 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 17 J/kg
- Mixed-layer CIN
- -45 J/kg
- Mixed-layer LCL
- 715 m above ground
- 0-6 km bulk shear
- 40 kt
- 0-1 km storm-relative helicity
- 14 m²/s²
- 0-3 km storm-relative helicity
- 56 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
294 WGUS61 KPHI 111945 FFAPHI URGENT - IMMEDIATE BROADCAST REQUESTED Flood Watch National Weather Service Mount Holly NJ 345 PM EDT Sun Jul 11 2021 NJZ001-007>010-012-120745- /O.NEW.KPHI.FF.A.0004.210712T1800Z-210713T0900Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Sussex-Warren-Morris-Hunterdon-Somerset-Middlesex- Including the cities of Flemington, Newton, Washington, Morristown, Somerville, and New Brunswick 345 PM EDT Sun Jul 11 2021 ...FLASH FLOOD WATCH IN EFFECT FROM MONDAY AFTERNOON THROUGH LATE MONDAY NIGHT... The National Weather Service in Mount Holly has issued a * Flash Flood Watch for portions of northern New Jersey...and northwest New Jersey...including the following areas...in northern New Jersey...Middlesex, Morris, Somerset, Sussex, and Warren. In northwest New Jersey...Hunterdon. * From Monday afternoon through late Monday night. * A stalled frontal boundary will lead to a period of moderate to heavy rain late Monday into Monday night. Overall, 1 to 3 inches of rain will fall with locally higher amounts. * Heavy rain in a short period of time may cause streams and creeks to rise quickly out of their banks. There is also the potential for flash flooding across more urbanized areas and those areas with poor drainage. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Flash Flood Watch means there is a potential for rapid-onset flooding based on current forecasts. You should monitor later forecasts and be alert for Flash Flood Warnings. && $$ Kruzdlo
4 follow-up statements
919 WGUS61 KPHI 120733 FFAPHI Flood Watch National Weather Service Mount Holly NJ 333 AM EDT Mon Jul 12 2021 NJZ001-007>010-012-121945- /O.CON.KPHI.FF.A.0004.210712T1800Z-210713T0900Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Sussex-Warren-Morris-Hunterdon-Somerset-Middlesex- Including the cities of Flemington, Newton, Washington, Morristown, Somerville, and New Brunswick 333 AM EDT Mon Jul 12 2021 ...FLASH FLOOD WATCH REMAINS IN EFFECT FROM 2 PM EDT THIS AFTERNOON THROUGH LATE TONIGHT... The Flash Flood Watch continues for * Portions of northern New Jersey...and northwest New Jersey... including the following areas...in northern New Jersey... Middlesex, Morris, Somerset, Sussex, and Warren. In northwest New Jersey...Hunterdon. * From 2 PM EDT this afternoon through late tonight. * A warm front will stall and slowly sag southward as a stationary front through tonight, leading to a period of moderate to heavy rain into tonight. Overall, 1 to 3 inches of rain will fall with locally higher amounts possible where thunderstorms train. * Heavy rain in a short period of time may cause streams and creeks to rise quickly out of their banks. There is also the potential for flash flooding across more urbanized areas and those areas with poor drainage. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Flash Flood Watch means there is a potential for rapid-onset flooding based on current forecasts. You should monitor later forecasts and be alert for Flash Flood Warnings. && $$ Davis
576 WGUS61 KPHI 121523 FFAPHI URGENT - IMMEDIATE BROADCAST REQUESTED Flood Watch National Weather Service Mount Holly NJ 1123 AM EDT Mon Jul 12 2021 NJZ013-015-017>019-PAZ054-055-060>062-070-071-101>106-130330- /O.EXB.KPHI.FF.A.0004.210712T1523Z-210713T0900Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Western Monmouth-Mercer-Gloucester-Camden-Northwestern Burlington- Carbon-Monroe-Berks-Lehigh-Northampton-Delaware-Philadelphia-Western Chester-Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-Lower Bucks- Including the cities of Glassboro, Jim Thorpe, Media, Philadelphia, Doylestown, Chalfont, Honey Brook, Lansdale, Norristown, Reading, Mount Holly, Cherry Hill, Moorestown, Freehold, Pottstown, Allentown, Oxford, Kennett Square, Easton, West Chester, Morrisville, Trenton, Collegeville, Camden, Bethlehem, Stroudsburg, and Perkasie 1123 AM EDT Mon Jul 12 2021 ...FLASH FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT... The National Weather Service in Mount Holly has expanded the * Flash Flood Watch to include portions of New Jersey...and Pennsylvania...including the following areas...in New Jersey... Camden, Gloucester, Mercer, Northwestern Burlington, and Western Monmouth. In Pennsylvania...Berks, Carbon, Delaware, Eastern Chester, Eastern Montgomery, Lehigh, Lower Bucks, Monroe, Northampton, Philadelphia, Upper Bucks, Western Chester, and Western Montgomery. * Through late tonight. * A near stationary frontal boundary combined with a hot and humid air mass will cause one or more rounds of thunderstorms with heavy rain to affect the area from this afternoon into tonight. Rainfall amounts could be highly variable, but a general 1 to 3 inches of rain with locally higher amounts is possible through tonight. * Heavy rain in a short period of time may cause streams and creeks to rise quickly out of their banks. There is also the potential for flash flooding across more urbanized areas and those areas with poor drainage. PRECAUTIONARY/PREPAREDNESS ACTIONS... You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued. && $$ NJZ001-007>010-012-130330- /O.EXT.KPHI.FF.A.0004.210712T1523Z-210713T0900Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Sussex-Warren-Morris-Hunterdon-Somerset-Middlesex- Including the cities of Flemington, Newton, Washington, Morristown, Somerville, and New Brunswick 1123 AM EDT Mon Jul 12 2021 ...FLASH FLOOD WATCH NOW IN EFFECT THROUGH LATE TONIGHT... The Flash Flood Watch is now in effect for * Portions of northern New Jersey...and northwest New Jersey... including the following areas...in northern New Jersey... Middlesex, Morris, Somerset, Sussex, and Warren. In northwest New Jersey...Hunterdon. * Through late tonight. * A near stationary frontal boundary combined with a hot and humid air mass will cause one or more rounds of thunderstorms with heavy rain to affect the area from this afternoon into tonight. Rainfall amounts could be highly variable, but a general 1 to 3 inches of rain with locally higher amounts is possible through tonight. * Heavy rain in a short period of time may cause streams and creeks to rise quickly out of their banks. There is also the potential for flash flooding across more urbanized areas and those areas with poor drainage. PRECAUTIONARY/PREPAREDNESS ACTIONS... You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued. && $$ JEO
530 WGUS61 KPHI 130301 FFAPHI Flood Watch National Weather Service Mount Holly NJ 1101 PM EDT Mon Jul 12 2021 NJZ001-007>010-012-013-015-017>019-PAZ054-055-060>062-070-071- 101>106-130900- /O.CON.KPHI.FF.A.0004.000000T0000Z-210713T0900Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Sussex-Warren-Morris-Hunterdon-Somerset-Middlesex-Western Monmouth- Mercer-Gloucester-Camden-Northwestern Burlington-Carbon-Monroe-Berks- Lehigh-Northampton-Delaware-Philadelphia-Western Chester-Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-Lower Bucks- Including the cities of Glassboro, Jim Thorpe, Flemington, Media, Philadelphia, Doylestown, Chalfont, Morristown, Honey Brook, Lansdale, Norristown, Reading, Mount Holly, Cherry Hill, Moorestown, Freehold, Pottstown, Allentown, Oxford, Kennett Square, Easton, West Chester, Morrisville, New Brunswick, Trenton, Newton, Washington, Collegeville, Camden, Bethlehem, Stroudsburg, Perkasie, and Somerville 1101 PM EDT Mon Jul 12 2021 ...FLASH FLOOD WATCH REMAINS IN EFFECT UNTIL 5 AM EDT TUESDAY... The Flash Flood Watch continues for * Portions of New Jersey...and Pennsylvania...including the following areas...in New Jersey...Camden, Gloucester, Hunterdon, Mercer, Middlesex, Morris, Northwestern Burlington, Somerset, Sussex, Warren, and Western Monmouth. In Pennsylvania...Berks, Carbon, Delaware, Eastern Chester, Eastern Montgomery, Lehigh, Lower Bucks, Monroe, Northampton, Philadelphia, Upper Bucks, Western Chester, and Western Montgomery. * Until 5 AM EDT Tuesday. * Most of the heavy rain has tapered off, but many areas picked up between 2 and 4 inches of rain, with a stripe of 6 to 10 inches of rain along the Interstate 95 corridor between Philadelphia and Trenton from this afternoon through this evening. Any additional rain through the overnight hours could result in more flash flooding. * Heavy rain in a short period of time may cause streams and creeks to rise quickly out of their banks. There is also the potential for flash flooding across more urbanized areas and those areas with poor drainage. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Flash Flood Watch means there is a potential for rapid-onset flooding based on current forecasts. You should monitor later forecasts and be alert for Flash Flood Warnings. && $$ MPS
786 WGUS61 KPHI 130741 FFAPHI Flood Watch National Weather Service Mount Holly NJ 341 AM EDT Tue Jul 13 2021 NJZ001-007>010-012-013-015-017>019-PAZ054-055-060>062-070-071- 101>106-130845- /O.CAN.KPHI.FF.A.0004.000000T0000Z-210713T0900Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Sussex-Warren-Morris-Hunterdon-Somerset-Middlesex-Western Monmouth- Mercer-Gloucester-Camden-Northwestern Burlington-Carbon-Monroe-Berks- Lehigh-Northampton-Delaware-Philadelphia-Western Chester-Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-Lower Bucks- Including the cities of Glassboro, Jim Thorpe, Flemington, Media, Philadelphia, Doylestown, Chalfont, Morristown, Honey Brook, Lansdale, Norristown, Reading, Mount Holly, Cherry Hill, Moorestown, Freehold, Pottstown, Allentown, Oxford, Kennett Square, Easton, West Chester, Morrisville, New Brunswick, Trenton, Newton, Washington, Collegeville, Camden, Bethlehem, Stroudsburg, Perkasie, and Somerville 341 AM EDT Tue Jul 13 2021 ...FLASH FLOOD WATCH IS CANCELLED... The Flash Flood Watch for portions of New Jersey...and Pennsylvania...including the following areas...in New Jersey... Camden, Gloucester, Hunterdon, Mercer, Middlesex, Morris, Northwestern Burlington, Somerset, Sussex, Warren, and Western Monmouth. In Pennsylvania...Berks, Carbon, Delaware, Eastern Chester, Eastern Montgomery, Lehigh, Lower Bucks, Monroe, Northampton, Philadelphia, Upper Bucks, Western Chester, and Western Montgomery has been cancelled. The Flood Watch is cancelled. Flooding is no longer expected to pose a threat. Please continue to heed remaining road closures. $$ MPS
The office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 11, 6:18 PM EDT | Heat Advisory | PHI | Burlington, Camden, Gloucester, Ocean | 50 hr |
Nearby
Flash Flood Watches in New Jersey, 2021Flash Flood Watches in Pennsylvania, 2021Every flash flood watch in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.