Alert archive / Pennsylvania / Areal Flood Advisories in 2020
Areal Flood Advisory 96, NWS Philadelphia/Mount Holly
NWS Philadelphia/Mount Holly issued this areal flood advisory at Jul 23, 2020, 11:10 PM EDT for Chester County, Delaware County, Pennsylvania; New Castle County, Delaware. It was in force for 2 hr.
The area
The counties it named.
The facts
- Issued
- Jul 23, 2020, 11:10 PM EDT (03:10 UTC)
- Expired
- Jul 24, 2020, 1:15 AM EDT
- In force
- 2 hr
- Issued by
- NWS Philadelphia/Mount Holly
- Area
- Storm-based polygon
Counties New Castle County, DE, Chester County, PA, Delaware County, PA
The radar
The Philadelphia radar (KDIX), 102 km from the middle of the area, began a volume at 03:11 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.
What forecasters said that day
The local office's own words before this areal flood advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Philadelphia/Mount Holly wrote its last area forecast discussion before this areal flood advisory went out at Jul 23, 3:28 PM EDT, 7 hours 42 minutes earlier.
Area forecast discussion, Jul 23, 3:28 PM EDT, 7 hours 42 minutes before
Area Forecast Discussion National Weather Service Mount Holly NJ 328 PM EDT Thu Jul 23 2020 .SYNOPSIS... A weak cold front will slowly sink southward through the region from tonight through Friday. The front will finally sink to our south by Saturday as high pressure builds in from the north and remains over us through Monday. A cold front will approach on Tuesday as low pressure tracks through southern Canada. That front should move through Tuesday night or Wednesday with another area of high pressure building in towards the end of the week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... A severe thunderstorm watch has been issued for north NJ and ne PA into the evening. Damaging winds are possible and also there is some threat for heavy rains as well. The watch will continue until 10 PM. Daytime heating along with an approaching front and improving upper dynamics will contribute to increasing chcs for showers and tstms for the rest of the afternoon and into the evening. The chcs will get higher N/W first then they will spread S/E for the early overnight. Locally heavy rains and gusty winds with some of the tstms. SPC maintains a slight risk for nrn NJ and NE PA for the present period with a marginal risk surrounding that. Winds seem to be the greatest threat with the nrn areas favored due to the presence of better mid- level winds across NY/New England. It will remain warm and humid overnight with lows only dropping into the mid/upper 60s for the north areas and low/mid 70s for Delmarva and srn NJ. Patchy fog may develop later tonight in areas that receive rain the rest of today. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Friday... Some low clouds and light fog across the area during the morning will mix out by mid-late morning with more showers and tstms developing across the area for the afternoon. Once again, very warm and humid with highs in the mid/upper 80s with dew points in the upper 60s to low 70s. Pops are in the chc range for now, but a higher chc is possible for some areas when it becomes clear which boundaries remain after todays convection. Friday night... Like today, scattered showers and tstms will be across the area with the weak front pushing thru the area. Activity will diminish overnight and patchy fog will develop overnight. Lows in the upper 60s to low 70s region-wide. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Overview... After an active stretch, a more benign pattern develops for the weekend and into next week. Ridging over the center of the country begins to shift east and gradually break down as a rather strong trough, the most robust we've seen in awhile, digs into the Great Lakes region. As the ridge folds over, a chunk of warmer air from out to the west will be advected towards the region, and is likely to lead to another uptick in the heat for the start of next week. The main surface feature to watch next week will be a cold front approaching from the west as low pressure tracks through southern Canada ahead of the approaching trough. Timing of this front remains uncertain (the overall trend is slower) but when it comes through it will likely bring a round of showers and thunderstorms. A trend towards high pressure and drier weather is then favored for late week. For sensible weather concerns this period, overall it looks like a fairly low impact stretch. Sunday through Tuesday will be quite hot and fairly humid. While each day will be marginal in terms of needing any heat advisories, the combined effects of these three days, continued warm overnights, and the recent lengthy stretch of similarly hot and humid conditions with no breaks may lead to some problems. Other than that, will monitor for any severe weather or hydro concerns with the frontal passage, but it does not look too alarming at the moment with shear on the weak side and the magnitude of frontal forcing in question. Dailies... Saturday-Saturday night... Raised PoPs a bit on Saturday (mostly slgt chc, some low end chc) especially to the south. This has seemed possible for awhile, and while Saturday by no means looks like a day with widespread showers and storms, does look like some isolated to widely scattered convection is possible. This is mainly driven by a continued warm and humid air mass and the continued nearby presence of the weak and diffuse surface front from earlier in the week. Additional surface boundaries such as the sea breeze may aid in producing isolated convection. Still a mainly dry day overall as high pressure will be starting to build in from the north. Warm and humid again Saturday with highs near 90 as the "cold front" to the south is very weak and will be mostly washed out by then. Sunday-Sunday night... Rain chances drop further on Sunday with weakening high pressure to the north moving a little further south. Still a warm and fairly humid air mass in place, but little forcing for ascent so while I can't totally rule out a shower especially over Delmarva or southern NJ, should be a mainly dry day and another warm night. Heat index values during the day Sunday rise towards 95 to 100, so approaching advisory criteria but more likely to stay below. Monday-Monday night... The trend is slower with the approach of a cold front next week as weak high pressure looks to remain our primary influence on Monday. Cut PoPs back to below mentionable levels on Monday. Monday will be quite hot ahead of the front, with highs getting into the low to mid 90s. Humidity, while not oppressive, will remain elevated, and heat index values may approach advisory criteria in some areas. Another warm and humid night. Tuesday-Wednesday... Likely to be the most active part of the period as low pressure tracks towards the southern Hudson Bay and into Quebec by midweek. A cold front will approach from the west as it does so and as a large trough digs into the Great Lakes. Ahead of the front, PWAT values will rise and humidity will probably peak on Tuesday, another very warm day. A band of showers and thunderstorms will likely move through ahead of the front, but the timing remains somewhat uncertain. Current trends favor the best rain chances being late Tuesday into Tuesday night. May dry out by Wednesday, but given what's happened with the last couple of cold fronts, would not be too surprised if this one also slows down enough to keep warmer and more humid air and even a storm risk still around on Wednesday, especially to the south. Am not currently too concerned with severe or hydro issues from this system. Wind fields look pretty weak and always worry about a lack of forcing with low centers tracking this far north. Just something to keep an eye on. Later next week... Once the midweek front passes, assuming it doesn't stall or wash out, then we should trend towards drier weather towards the end of next week. With the more robust troughing digging in to our west, we may finally see a somewhat more substantial drop in temperatures or at least humidity towards the end of next week, but still some uncertainty on that. && .AVIATION /19Z THURSDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...Scattered to numerous showers and tstms across the area this evening will decrease in coverage overnight. Areas of fog are possible once the rains end and skies clear partially. Timing for the rains and thunder look to be early N/W and more towards mid- evening S/E. Winds will generally be southwest to west at 5 to 10 mph but locally higher in and near tstms. Confid is medium at best. Friday...There will be some local restrictions in CIGS and VSBYS in the morning during the pre-mixing period with some areas of low level moisture across the region. After mixing occurs, mostly VFR is expected across the area. Scattered showers and tstms will again develop with more restrictions possible. Outlook... Fri night...Showers and scattered tstms ending and localized fog developing. Saturday-Saturday night... Mainly VFR during the day Saturday. Slight chance of afternoon showers or thunderstorms mainly near and south of PHL. Overnight, fog development is possible, with some areas of IFR or lower possible. Winds light and variable. High confidence overall except low confidence in how widespread fog will be overnight. Sunday-Sunday night... Mainly VFR. Patchy fog possible Sunday morning. Southwest wind 5 to 10 kt. Moderate to high confidence. Monday-Monday night... Mainly VFR. Southwest wind 5 to 10 kt. Moderate to high confidence. Tuesday-Wednesday... Prevailing VFR, but a band of showers and thunderstorms will likely move through the region ahead of a cold front with a period of restrictions. Winds mainly west-southwest at 5 to 10 kt, becoming more west or west-northwest on Wednesday. Low confidence. && .MARINE... A summerlike pattern continuing with sub-SCA conditions exected along with late afternoon/evening scattered showers and tstms later today and Friday. Winds will be mostly west to southwest at around 10 knots much of the time. Locally winds winds and seas near tstms. Outlook... Through Tuesday night... No marine headlines are anticipated. Mainly dry weather expected over the waters with only isolated tstms possible Saturday. Light southeast winds on Saturday then mainly SW at 10 to 15 kt for the remainder of the period. Seas 2 to 4 ft. Fri night...sub-SCA expected. Scattered evening showers and tstms mostly for the DE and srn NJ waters. Rip Currents... With light winds and seas continuing, the risk for the formation of dangerous rip currents is expected to remain low through Friday. && .EQUIPMENT... The NOAA Weather Radio All-Hazards broadcast from Hibernia Park, Pennsylvania (Station WNG-704) will remain off the air until further notice due to damage suffered in the June 3 derecho. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && Synopsis...O'Brien Near Term...O'Hara Short Term...O'Hara Long Term...O'Brien Aviation...O'Brien/O'Hara Marine...O'Brien/O'Hara Equipment...WFO PHI
Hazardous weather outlook, Jul 23, 3:23 PM EDT, 7 hours 47 minutes before
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Special weather statement, Jul 23, 6:53 PM EDT, 4 hours 17 minutes before
Special Weather Statement
National Weather Service Mount Holly NJ
653 PM EDT Thu Jul 23 2020
NJZ015-PAZ106-232330-
Mercer-Lower Bucks-
653 PM EDT Thu Jul 23 2020
...A STRONG THUNDERSTORM WILL AFFECT MERCER AND EAST CENTRAL BUCKS
COUNTIES...
At 652 PM EDT, a strong thunderstorm was located over Ewing, or over
Trenton, moving east at 20 mph.
Wind gusts up to 40 mph and pea size hail are possible with this
storm.
Heavy rainfall is also occurring with this storm...and may cause
ponding on roadways and poor drainage areas. Do not drive your
vehicle through flooded roadways.
Occasional cloud to ground lightning is occurring with this storm.
Lightning can strike 15 miles away from a thunderstorm. If you see
lightning or hear thunder seek a safe shelter inside a building or
vehicle.
Locations impacted include...
Trenton, Ewing, Princeton, Pennington, Yardley, Edinburg, White
Horse, Windsor, Mercerville-Hamilton Square, Lawrenceville, Woodside,
Plainsboro Center, Kingston, Levittown, Morrisville, Princeton
Junction, Woodbourne, Princeton North, Fairless Hills and
Yardville-Groveville.
This includes the following highways...
New Jersey Turnpike near exit 8.
Interstate 195 in New Jersey between mile markers 0 and 8.
Interstate 295 in New Jersey between mile markers 60 and 76.
If outdoors, consider seeking shelter inside a building.
LAT...LON 4019 7456 4017 7488 4027 7491 4039 7463
4037 7462 4034 7463 4032 7459 4022 7454
TIME...MOT...LOC 2252Z 252DEG 19KT 4024 7480
RobertsonSpecial weather statement, Jul 23, 7:10 PM EDT, 4 hours before
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Special Weather Statement
National Weather Service Mount Holly NJ
729 PM EDT Thu Jul 23 2020
NJZ012-013-015-020-240000-
Ocean-Western Monmouth-Middlesex-Mercer-
729 PM EDT Thu Jul 23 2020
...A STRONG THUNDERSTORM WILL AFFECT NORTHERN OCEAN...SOUTHEASTERN
MERCER...WESTERN MONMOUTH AND SOUTHERN MIDDLESEX COUNTIES...
At 729 PM EDT, a strong thunderstorm was located over Roosevelt, or
15 miles east of Trenton, moving east at 20 mph.
Wind gusts up to 40 mph and pea size hail are possible with this
storm.
Heavy rainfall is also occurring with this storm...and may cause
ponding on roadways and poor drainage areas. Do not drive your
vehicle through flooded roadways.
Occasional cloud to ground lightning is occurring with this storm.
Lightning can strike 15 miles away from a thunderstorm. If you see
lightning or hear thunder seek a safe shelter inside a building or
vehicle.
Locations impacted include...
Toms River, Lakewood, Old Bridge, Jackson, Howell, East Brunswick,
Marlboro, Manalapan, Matawan, Jamesburg, Hightstown, Cranbury,
Allentown, Roosevelt, Leisure Village, Windsor, Princeton Meadows,
Brownville, East Freehold and Six Flags Theme Park.
This includes the following highways...
New Jersey Turnpike between exits 8A and 9.
Interstate 195 in New Jersey between mile markers 8 and 30.
Garden State Parkway between mile markers 87 and 90, and near mile
marker 121.
LAT...LON 4001 7414 4008 7456 4014 7459 4035 7461
4044 7425
TIME...MOT...LOC 2329Z 266DEG 19KT 4021 7447
RobertsonLocal storm report, Jul 23, 7:32 PM EDT, 3 hours 38 minutes before
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Special Weather Statement
National Weather Service Mount Holly NJ
752 PM EDT Thu Jul 23 2020
NJZ012>014-020-026-240030-
Eastern Monmouth-Coastal Ocean-Ocean-Western Monmouth-Middlesex-
752 PM EDT Thu Jul 23 2020
...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NORTHEASTERN OCEAN...
MONMOUTH AND SOUTHEASTERN MIDDLESEX COUNTIES...
At 751 PM EDT, radar indicated strong thunderstorms were located
along a line extending from Robertsville to West Freehold to Six
Flags Theme Park. Movement was east at 25 mph.
Wind gusts up to 40 mph and pea size hail are possible with these
storms.
Locations impacted include...
Long Branch, Asbury Park, Sandy Hook, Lakewood, Middletown, Old
Bridge, Howell, Marlboro, Tinton Falls, Holmdel, Red Bank, Matawan,
Manasquan, Highlands, Point Pleasant Beach, Farmingdale, Allenwood,
Brownville, East Freehold and Six Flags Theme Park.
This includes the following highways...
Interstate 195 in New Jersey between mile markers 17 and 34.
Garden State Parkway between mile markers 91 and 121.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 15 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
LAT...LON 4032 7396 4006 7404 4011 7449 4021 7438
4039 7439 4045 7421 4044 7420 4046 7418
4041 7400 4041 7399 4044 7399 4048 7402
4047 7399 4044 7398
TIME...MOT...LOC 2351Z 260DEG 21KT 4034 7430 4023 7428 4014 7440
StaarmannThe office that day
Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 23, 8:04 PM EDT | Severe Thunderstorm Warning | PHI | Middlesex, Monmouth | 26 min |
| Jul 23, 11:16 PM EDT | Severe Thunderstorm Warning | PHI | Gloucester, Salem | 44 min |
| Jul 23, 11:27 PM EDT | Special Marine Warning | PHI | 63 min | |
| Jul 24, 12:14 AM EDT | Special Weather Statement | PHI | Middlesex | 31 min |
| Jul 24, 12:23 AM EDT | Severe Thunderstorm Warning | PHI | Mercer, Middlesex, Monmouth, Somerset | 52 min |
| Jul 24, 12:31 AM EDT | Areal Flood Advisory | PHI | Hunterdon, Mercer, Middlesex, Monmouth, Somerset | 119 min |
| Jul 24, 12:51 AM EDT | Special Marine Warning | PHI | 54 min | |
| Jul 24, 1:13 AM EDT | Severe Thunderstorm Warning | PHI | Hunterdon, Mercer, Middlesex, Monmouth, Somerset | 62 min |
| Jul 24, 1:28 AM EDT | Flash Flood Warning | PHI | Mercer, Middlesex, Monmouth, Somerset | 4 hr |
| Jul 24, 1:36 AM EDT | Special Marine Warning | PHI | 84 min | |
| Jul 24, 2:18 AM EDT | Severe Thunderstorm Warning | PHI | Hunterdon, Middlesex, Morris, Somerset | 42 min |
| Jul 24, 5:04 AM EDT | Special Marine Warning | PHI | 56 min | |
| Jul 24, 10:43 AM EDT | Flash Flood Warning | PHI | Camden | 76 min |
| Jul 24, 11:42 AM EDT | Special Marine Warning | PHI | 63 min | |
| Jul 24, 12:43 PM EDT | Areal Flood Advisory | PHI | Ocean | 3 hr |
| Jul 24, 1:09 PM EDT | Areal Flood Advisory | PHI | Monmouth, Ocean | 110 min |
| Jul 24, 1:40 PM EDT | Special Weather Statement | PHI | Atlantic | 35 min |
| Jul 24, 1:43 PM EDT | Areal Flood Advisory | PHI | Burlington, Mercer, Monmouth | 3 hr |
| Jul 24, 2:02 PM EDT | Areal Flood Advisory | PHI | Atlantic, Burlington, Camden, Gloucester | 3 hr |
| Jul 24, 2:19 PM EDT | Areal Flood Advisory | PHI | Burlington, Camden, Gloucester | 2 hr |
| Jul 24, 2:26 PM EDT | Flash Flood Warning | PHI | Burlington | 2 hr |
| Jul 24, 2:39 PM EDT | Areal Flood Advisory | PHI | Burlington, Ocean | 3 hr |
| Jul 24, 2:42 PM EDT | Areal Flood Advisory | PHI | Burlington, Ocean | 2 hr |
| Jul 24, 3:34 PM EDT | Flash Flood Warning | PHI | Atlantic, Burlington, Ocean | 2 hr |
| Jul 24, 4:22 PM EDT | Areal Flood Advisory | PHI | Atlantic, Cape May | 3 hr |
| Jul 24, 4:58 PM EDT | Areal Flood Advisory | PHI | Cape May | 2 hr |
| Jul 23, 10:26 PM EDT | Severe Thunderstorm Warning | PHI | Chester | 49 min |
| Jul 23, 10:44 PM EDT | Areal Flood Advisory | PHI | Chester | 2 hr |
| Jul 23, 11:38 PM EDT | Special Weather Statement | PHI | Chester | 37 min |
| Jul 23, 11:44 PM EDT | Severe Thunderstorm Warning | PHI | Chester, Delaware, Montgomery, Philadelphia | 46 min |
| Jul 24, 12:24 AM EDT | Flash Flood Warning | PHI | Chester | 114 min |
| Jul 24, 12:32 AM EDT | Special Weather Statement | PHI | Bucks, Montgomery | 28 min |
| Jul 24, 12:42 AM EDT | Severe Thunderstorm Warning | PHI | Bucks, Montgomery | 48 min |
| Jul 23, 11:00 PM EDT | Severe Thunderstorm Warning | PHI | New Castle | 45 min |
| Jul 24, 12:37 AM EDT | River Flood Warning | PHI | New Castle | 102 min |
| Jul 24, 4:35 PM EDT | Special Weather Statement | PHI | New Castle | 25 min |
| Jul 24, 5:34 PM EDT | Special Weather Statement | PHI | Sussex | 26 min |
Nearby
Areal Flood Advisories in Pennsylvania, 2020Areal Flood Advisories in Delaware, 2020Every areal flood advisory in 2020
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; radar from the NEXRAD Level II archive.