Alert archive / New Jersey / Excessive Heat Watches in 2021

Excessive Heat Watch 1, NWS Philadelphia/Mount Holly

August 9, 20215 counties in Pennsylvania; New Castle County, Delaware; 10 counties in New Jersey

NWS Philadelphia/Mount Holly issued this excessive heat watch at Aug 9, 2021, 3:43 PM EDT for 5 counties in Pennsylvania; New Castle County, Delaware; 10 counties in New Jersey. It took effect at Aug 11, 2021, 12:00 PM EDT. It was in force for .

The area

The counties it named.

The facts

Issued
Aug 9, 2021, 3:43 PM EDT (19:43 UTC)
In effect from
Aug 11, 2021, 12:00 PM EDT
Expired
Aug 10, 2021, 3:33 AM EDT
In force
Issued by
NWS Philadelphia/Mount Holly

Counties New Castle County, DE, Burlington County, NJ, Camden County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Morris County, NJ, Ocean County, NJ, Somerset County, NJ, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 49 km from the middle of the area, began a volume at 19:43 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, 7.7 hours before the alert went out and 192 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.

Skew-T log-pSkew-T log-p diagram, Brookhaven, NY at 12:00Z on 2021-08-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 12 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Brookhaven, NY at 12:00Z on 2021-08-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -2 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
12 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
473 m above ground
0-6 km bulk shear
14 kt
0-1 km storm-relative helicity
-2 m²/s²
0-3 km storm-relative helicity
10 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

273 
WWUS71 KPHI 091943
NPWPHI

URGENT - WEATHER MESSAGE
National Weather Service Mount Holly NJ
343 PM EDT Mon Aug 9 2021

DEZ001-NJZ008>010-012-013-015-017>020-027-PAZ070-071-101>106-
101200-
/O.NEW.KPHI.EH.A.0001.210811T1600Z-210814T0000Z/
New Castle-Morris-Hunterdon-Somerset-Middlesex-Western Monmouth-
Mercer-Gloucester-Camden-Northwestern Burlington-Ocean-
Southeastern Burlington-Delaware-Philadelphia-Western Chester-
Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-
Lower Bucks-
Including the cities of Wilmington, Morristown, Flemington, 
Somerville, New Brunswick, Freehold, Trenton, Glassboro, Camden, 
Cherry Hill, Moorestown, Mount Holly, Jackson, 
Wharton State Forest, Media, Philadelphia, Honey Brook, Oxford, 
West Chester, Kennett Square, Collegeville, Pottstown, 
Norristown, Lansdale, Chalfont, Perkasie, Morrisville, 
and Doylestown
343 PM EDT Mon Aug 9 2021

...EXCESSIVE HEAT WATCH IN EFFECT FROM WEDNESDAY AFTERNOON
THROUGH FRIDAY EVENING...

* WHAT...Dangerously hot conditions with heat index values around 105
  possible.

* WHERE...Portions of central, northern, northwest and southern 
  New Jersey, southeast Pennsylvania and northern Delaware.

* WHEN...From Wednesday afternoon through Friday evening.

* IMPACTS...Extreme heat and humidity will significantly 
  increase the potential for heat related illnesses, 
  particularly for those working or participating in outdoor 
  activities.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the latest forecasts and warnings for updates on this
situation. Be prepared to drink plenty of fluids, stay in an air-
conditioned room, stay out of the sun, and check up on relatives
and neighbors.

Young children and pets should never be left unattended in
vehicles under any circumstances. This is especially true during
warm or hot weather when car interiors can reach lethal
temperatures in a matter of minutes.

&&

$$
1 follow-up statement
810 
WWUS71 KPHI 100733
NPWPHI

URGENT - WEATHER MESSAGE
National Weather Service Mount Holly NJ
333 AM EDT Tue Aug 10 2021

DEZ001-NJZ008>010-012-013-015-017>020-027-PAZ070-071-101>106-
102130-
/O.UPG.KPHI.EH.A.0001.210811T1600Z-210814T0000Z/
/O.NEW.KPHI.EH.W.0002.210811T1600Z-210813T0000Z/
New Castle-Morris-Hunterdon-Somerset-Middlesex-Western Monmouth-
Mercer-Gloucester-Camden-Northwestern Burlington-Ocean-
Southeastern Burlington-Delaware-Philadelphia-Western Chester-
Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-
Lower Bucks-
Including the cities of Wilmington, Morristown, Flemington, 
Somerville, New Brunswick, Freehold, Trenton, Glassboro, Camden, 
Cherry Hill, Moorestown, Mount Holly, Jackson, 
Wharton State Forest, Media, Philadelphia, Honey Brook, Oxford, 
West Chester, Kennett Square, Collegeville, Pottstown, 
Norristown, Lansdale, Chalfont, Perkasie, Morrisville, 
and Doylestown
333 AM EDT Tue Aug 10 2021

...EXCESSIVE HEAT WARNING IN EFFECT FROM NOON WEDNESDAY TO 8 PM
EDT THURSDAY...

* WHAT...Dangerously hot conditions with heat index values to
  around 105 on Wednesday and up to 110 Thursday.

* WHERE...Portions of central, northern, northwest and southern 
  New Jersey, southeast Pennsylvania and northern Delaware.

* WHEN...From noon Wednesday to 8 PM EDT Thursday.

* IMPACTS...Extreme heat and humidity will significantly 
  increase the potential for heat related illnesses, 
  particularly for those working or participating in outdoor 
  activities.

* ADDITIONAL DETAILS...An extended period of excessively hot and
  humid conditions is expected Wednesday and Thursday and may
  continue through Friday. Overnight low temperatures in the mid
  70s will not provide much relief from the heat. The hottest
  period is expected Thursday and Thursday night.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Drink plenty of fluids, stay in an air-conditioned room, stay out
of the sun, and check up on relatives and neighbors. Young
children and pets should never be left unattended in vehicles
under any circumstances.

Take extra precautions if you work or spend time outside. When
possible reschedule strenuous activities to early morning or
evening. Know the signs and symptoms of heat exhaustion and heat
stroke. Wear lightweight and loose fitting clothing when
possible. To reduce risk during outdoor work, the Occupational
Safety and Health Administration recommends scheduling frequent
rest breaks in shaded or air conditioned environments. Anyone
overcome by heat should be moved to a cool and shaded location.
Heat stroke is an emergency! Call 9 1 1.

&&

$$

NJZ001-007-014-026-PAZ060>062-102130-
/O.NEW.KPHI.HT.Y.0008.210811T1600Z-210813T0000Z/
Sussex-Warren-Eastern Monmouth-Coastal Ocean-Berks-Lehigh-
Northampton-
Including the cities of Newton, Washington, Sandy Hook, 
Long Beach Island, Reading, Allentown, Bethlehem, and Easton
333 AM EDT Tue Aug 10 2021

...HEAT ADVISORY IN EFFECT FROM NOON WEDNESDAY TO 8 PM EDT
THURSDAY...

* WHAT...Heat index values to around 100 on Wednesday and up to
  104 Thursday.

* WHERE...In New Jersey, Sussex, Warren, Eastern Monmouth and 
  Coastal Ocean. In Pennsylvania, Berks, Lehigh and Northampton.

* WHEN...From noon Wednesday to 8 PM EDT Thursday.

* IMPACTS...Hot temperatures and high humidity may cause heat 
  illnesses to occur.

* ADDITIONAL DETAILS...An extended period of hot and humid
  conditions is expected Wednesday and Thursday and may continue
  through Friday. Overnight low temperatures in the low to mid 
  70s will not provide much relief from the heat. The hottest 
  period is expected Thursday and Thursday night.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Drink plenty of fluids, stay in an air-conditioned room, stay out
of the sun, and check up on relatives and neighbors. Young
children and pets should never be left unattended in vehicles
under any circumstances.

Take extra precautions if you work or spend time outside. When
possible reschedule strenuous activities to early morning or
evening. Know the signs and symptoms of heat exhaustion and heat
stroke. Wear lightweight and loose fitting clothing when
possible. To reduce risk during outdoor work, the Occupational
Safety and Health Administration recommends scheduling frequent
rest breaks in shaded or air conditioned environments. Anyone
overcome by heat should be moved to a cool and shaded location.
Heat stroke is an emergency! Call 9 1 1.

&&

$$

DEZ002-003-MDZ012-015-019-020-NJZ016-021-022-102130-
/O.NEW.KPHI.HT.Y.0008.210811T1600Z-210813T0000Z/
Kent-Inland Sussex-Kent MD-Queen Annes-Talbot-Caroline-Salem-
Cumberland-Atlantic-
Including the cities of Dover, Georgetown, Chestertown, 
Centreville, Easton, Denton, Pennsville, Millville, and Hammonton
333 AM EDT Tue Aug 10 2021

...HEAT ADVISORY IN EFFECT FROM NOON WEDNESDAY TO 8 PM EDT
THURSDAY...

* WHAT...Heat index values to around 105 expected.

* WHERE...In New Jersey, Salem, Cumberland and Atlantic. In 
  Maryland, Kent MD, Queen Annes, Talbot and Caroline. In 
  Delaware, Kent and Inland Sussex.

* WHEN...From noon Wednesday to 8 PM EDT Thursday.

* IMPACTS...Hot temperatures and high humidity may cause heat 
  illnesses to occur.

* ADDITIONAL DETAILS...An extended period of hot and humid
  conditions is expected Wednesday and Thursday and may continue
  through Friday. Overnight low temperatures in the mid 70s will 
  not provide much relief from the heat. The hottest period is 
  expected Thursday and Thursday night.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Drink plenty of fluids, stay in an air-conditioned room, stay out
of the sun, and check up on relatives and neighbors. Young
children and pets should never be left unattended in vehicles
under any circumstances.

Take extra precautions if you work or spend time outside. When
possible reschedule strenuous activities to early morning or
evening. Know the signs and symptoms of heat exhaustion and heat
stroke. Wear lightweight and loose fitting clothing when
possible. To reduce risk during outdoor work, the Occupational
Safety and Health Administration recommends scheduling frequent
rest breaks in shaded or air conditioned environments. Anyone
overcome by heat should be moved to a cool and shaded location.
Heat stroke is an emergency! Call 9 1 1.

&&

$$

Staarmann

The office that day

Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 9, 4:36 PM EDTAreal Flood AdvisoryPHIChester, Delaware104 min
Aug 9, 5:12 PM EDTAreal Flood AdvisoryPHIChester, Delaware85 min
Aug 9, 5:34 PM EDTSpecial Weather StatementPHIPhiladelphia26 min
Aug 9, 5:40 PM EDTAreal Flood AdvisoryPHIPhiladelphia82 min
Aug 9, 6:10 PM EDTSpecial Weather StatementPHIPhiladelphia35 min
Aug 9, 6:24 PM EDTSpecial Weather StatementPHILehigh36 min
Aug 9, 6:29 PM EDTAreal Flood AdvisoryPHIBerks, Montgomery70 min
Aug 9, 6:49 PM EDTSpecial Weather StatementPHIMontgomery26 min
Aug 9, 7:14 PM EDTSpecial Weather StatementPHICarbon31 min
Aug 9, 2:10 PM EDTSpecial Weather StatementPHISussex50 min
Aug 9, 2:41 PM EDTAreal Flood AdvisoryPHIKent, New Castle, Sussex3 hr
Aug 9, 3:01 PM EDTFlash Flood WarningPHIKent, Sussex2 hr
Aug 9, 4:35 PM EDTSevere Thunderstorm WarningPHIKent40 min
Aug 9, 4:59 PM EDTFlash Flood WarningPHIKent79 min
Aug 9, 5:12 PM EDTSevere Thunderstorm WarningPHIKent20 min
Aug 9, 4:45 PM EDTSpecial Weather StatementPHIAtlantic30 min
Aug 9, 6:37 PM EDTSpecial Weather StatementPHIMercer38 min

Nearby

Excessive Heat Watches in New Jersey, 2021Excessive Heat Watches in Pennsylvania, 2021Excessive Heat Watches in Delaware, 2021Every excessive heat 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.