Alert archive / New Jersey / Freeze Watches in 2021

Freeze Watch 2, NWS Philadelphia/Mount Holly

April 20, 20215 counties in New Jersey; 5 counties in Pennsylvania

NWS Philadelphia/Mount Holly issued this freeze watch at Apr 20, 2021, 8:48 PM EDT for 5 counties in New Jersey; 5 counties in Pennsylvania. It took effect at Apr 22, 2021, 2:00 AM EDT. It was in force for .

The area

The counties it named.

The facts

Issued
Apr 20, 2021, 8:48 PM EDT (00:48 UTC)
In effect from
Apr 22, 2021, 2:00 AM EDT
Expired
Apr 21, 2021, 3:26 AM EDT
In force
Issued by
NWS Philadelphia/Mount Holly

Counties Hunterdon County, NJ, Morris County, NJ, Somerset County, NJ, Sussex County, NJ, Warren County, NJ, Berks County, PA, Bucks County, PA, Lehigh County, PA, Montgomery County, PA, Northampton County, PA

The radar

The Philadelphia radar (KDIX), 96 km from the middle of the area, began a volume at 00:48 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 00:00Z, 0.8 hours before the alert went out and 191 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 00:00Z on 2021-04-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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 00:00Z on 2021-04-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 152 square meters per square second.1939587897Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1938 m above ground
0-6 km bulk shear
39 kt
0-1 km storm-relative helicity
152 m²/s²
0-3 km storm-relative helicity
161 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

394 
WWUS71 KPHI 210048
NPWPHI

URGENT - WEATHER MESSAGE
National Weather Service Mount Holly NJ
848 PM EDT Tue Apr 20 2021

NJZ001-007-008-PAZ061-062-211400-
/O.NEW.KPHI.FZ.A.0002.210422T0600Z-210422T1300Z/
Sussex-Warren-Morris-Lehigh-Northampton-
Including the cities of Newton, Washington, Morristown, 
Allentown, Bethlehem, and Easton
848 PM EDT Tue Apr 20 2021

...FREEZE WATCH IN EFFECT FROM LATE WEDNESDAY NIGHT THROUGH
THURSDAY MORNING...

* WHAT...Sub-freezing temperatures as low as 29 possible.

* WHERE...In New Jersey, Sussex, Warren and Morris. In 
  Pennsylvania, Lehigh and Northampton.

* WHEN...From late Wednesday night through Thursday morning.

* IMPACTS...Frost and freeze conditions will kill crops and 
  other sensitive vegetation.

* ADDITIONAL DETAILS...Breezy conditions should prevent frost
  formation, however below freezing temperatures are possible
  Wednesday night and early Thursday morning.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold.

&&

$$

NJZ009-010-PAZ060-103-105-211400-
/O.NEW.KPHI.FZ.A.0002.210422T0600Z-210422T1300Z/
Hunterdon-Somerset-Berks-Western Montgomery-Upper Bucks-
Including the cities of Flemington, Somerville, Reading, 
Collegeville, Pottstown, Chalfont, and Perkasie
848 PM EDT Tue Apr 20 2021

...FREEZE WATCH IN EFFECT FROM LATE WEDNESDAY NIGHT THROUGH
THURSDAY MORNING...

* WHAT...Sub-freezing temperatures as low as 31 possible.

* WHERE...In New Jersey, Hunterdon and Somerset. In 
  Pennsylvania, Berks, Western Montgomery and Upper Bucks.

* WHEN...From late Wednesday night through Thursday morning.

* IMPACTS...Frost and freeze conditions will kill crops and 
  other sensitive vegetation.

* ADDITIONAL DETAILS...Breezy conditions should prevent frost
  formation, however below freezing temperatures are possible
  Wednesday night and early Thursday morning.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold.

&&

$$

Staarmann
1 follow-up statement
031 
WWUS71 KPHI 210726
NPWPHI

URGENT - WEATHER MESSAGE
National Weather Service Mount Holly NJ
326 AM EDT Wed Apr 21 2021

NJZ001-007>010-PAZ060>062-103-105-212100-
/O.UPG.KPHI.FZ.A.0002.210422T0600Z-210422T1300Z/
/O.NEW.KPHI.FZ.W.0003.210422T0500Z-210422T1300Z/
Sussex-Warren-Morris-Hunterdon-Somerset-Berks-Lehigh-Northampton-
Western Montgomery-Upper Bucks-
Including the cities of Newton, Washington, Morristown, 
Flemington, Somerville, Reading, Allentown, Bethlehem, Easton, 
Collegeville, Pottstown, Chalfont, and Perkasie
326 AM EDT Wed Apr 21 2021

...FREEZE WARNING IN EFFECT FROM 1 AM TO 9 AM EDT THURSDAY...

* WHAT...Sub-freezing temperatures in the mid 20s to lower 30s
  expected.

* WHERE...In New Jersey, Sussex, Warren, Morris, Hunterdon, and
  Somerset Counties. In Pennsylvania, Berks, Lehigh, Northampton,
  Western Montgomery, and Upper Bucks Counties.

* WHEN...From 1 AM to 9 AM EDT Thursday.

* IMPACTS...Frost and freeze conditions will kill crops and 
  other sensitive vegetation.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold.

&&

$$

PAZ101-102-212100-
/O.NEW.KPHI.FZ.W.0003.210422T0500Z-210422T1300Z/
Western Chester-Eastern Chester-
Including the cities of Honey Brook, Oxford, West Chester, 
and Kennett Square
326 AM EDT Wed Apr 21 2021

...FREEZE WARNING IN EFFECT FROM 1 AM TO 9 AM EDT THURSDAY...

* WHAT...Sub-freezing temperatures around 30 degrees expected.

* WHERE...Chester County in Pennsylvania.

* WHEN...From 1 AM to 9 AM EDT Thursday.

* IMPACTS...Frost and freeze conditions will kill crops and 
  other sensitive vegetation.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold.

&&

$$

CMS

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 21, 3:26 AM EDTFreeze WarningPHIHunterdon, Morris, Somerset, Sussex, Warren30 hr
Apr 21, 12:25 PM EDTSevere Thunderstorm WarningPHIWarren50 min
Apr 21, 12:51 PM EDTSevere Thunderstorm WarningPHISussex, Warren21 min
Apr 21, 12:55 PM EDTSevere Thunderstorm WarningPHIHunterdon, Warren27 min
Apr 21, 1:10 PM EDTSevere Thunderstorm WarningPHIBurlington, Camden, Gloucester, Mercer, Salem50 min
Apr 21, 1:17 PM EDTSpecial Weather StatementPHIHunterdon, Morris, Somerset, Sussex58 min
Apr 21, 1:28 PM EDTSevere Thunderstorm WarningPHIAtlantic, Burlington, Camden, Gloucester36 min
Apr 21, 1:30 PM EDTSpecial Marine WarningPHI60 min
Apr 21, 1:43 PM EDTSevere Thunderstorm WarningPHIHunterdon, Middlesex, Morris, Somerset33 min
Apr 21, 1:58 PM EDTSpecial Weather StatementPHIBurlington, Camden, Monmouth, Ocean62 min
Apr 21, 2:02 PM EDTSevere Thunderstorm WarningPHIBurlington, Camden, Monmouth, Ocean43 min
Apr 21, 2:03 PM EDTSpecial Weather StatementPHICumberland27 min
Apr 21, 2:17 PM EDTSevere Thunderstorm WarningPHIAtlantic, Cumberland, Gloucester, Salem43 min
Apr 21, 2:28 PM EDTSpecial Weather StatementPHIMiddlesex, Monmouth47 min
Apr 21, 2:30 PM EDTSpecial Marine WarningPHI60 min
Apr 21, 2:38 PM EDTSevere Thunderstorm WarningPHIMonmouth, Ocean37 min
Apr 21, 2:40 PM EDTSpecial Marine WarningPHI55 min
Apr 21, 2:43 PM EDTSpecial Weather StatementPHICape May32 min
Apr 21, 2:50 PM EDTSevere Thunderstorm WarningPHIAtlantic, Burlington, Ocean40 min
Apr 21, 3:02 PM EDTSevere Thunderstorm WarningPHIAtlantic28 min
Apr 21, 3:07 PM EDTSpecial Marine WarningPHI53 min
Apr 21, 12:03 PM EDTSpecial Weather StatementPHIChester, Lehigh42 min
Apr 21, 12:17 PM EDTSevere Thunderstorm WarningPHIBerks, Bucks, Chester, Lehigh, Montgomery, Northampton43 min
Apr 21, 12:54 PM EDTSpecial Weather StatementPHIDelaware36 min

Nearby

Freeze Watches in New Jersey, 2021Freeze Watches in Pennsylvania, 2021Every freeze 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.