Alert archive / New Jersey / Frost Advisories in 2021

Frost Advisory 1, NWS Philadelphia/Mount Holly

April 22, 20214 states

NWS Philadelphia/Mount Holly issued this frost advisory at Apr 22, 2021, 2:31 PM EDT for 4 states. It took effect at Apr 23, 2021, 1:00 AM EDT. It was in force for 7 hr.

The area

The counties it named.

The facts

Issued
Apr 22, 2021, 2:31 PM EDT (18:31 UTC)
In effect from
Apr 23, 2021, 1:00 AM EDT
Expired
Apr 23, 2021, 7:48 AM EDT
In force
7 hr
Issued by
NWS Philadelphia/Mount Holly

Counties Kent County, DE, New Castle County, DE, Sussex County, DE, Caroline County, MD, Kent County, MD, Queen Anne's County, MD, Talbot County, MD, Burlington County, NJ, Camden County, NJ, Gloucester County, NJ, Salem County, NJ, Delaware County, PA, Philadelphia County, PA

The radar

The Dover AFB radar (KDOX), 64 km from the middle of the area, began a volume at 18:30 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 6.5 hours before the alert went out and 163 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, Wallops Is Stn, VA at 12:00Z on 2021-04-22Temperature 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, Wallops Is Stn, VA at 12:00Z on 2021-04-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -116 square meters per square second.1939587897117136156Sfc1 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
1590 m above ground
0-6 km bulk shear
104 kt
0-1 km storm-relative helicity
-116 m²/s²
0-3 km storm-relative helicity
-31 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

417 
WWUS71 KPHI 221831
NPWPHI

URGENT - WEATHER MESSAGE
National Weather Service Mount Holly NJ
231 PM EDT Thu Apr 22 2021

NJZ001-007>010-012-013-015-020>022-027-PAZ060>062-101>106-231000-
/O.UPG.KPHI.FZ.A.0003.210423T0500Z-210423T1300Z/
/O.NEW.KPHI.FZ.W.0004.210423T0500Z-210423T1300Z/
Sussex-Warren-Morris-Hunterdon-Somerset-Middlesex-
Western Monmouth-Mercer-Ocean-Cumberland-Atlantic-
Southeastern Burlington-Berks-Lehigh-Northampton-Western Chester-
Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-
Lower Bucks-
Including the cities of Newton, Washington, Morristown, 
Flemington, Somerville, New Brunswick, Freehold, Trenton, 
Jackson, Millville, Hammonton, Wharton State Forest, Reading, 
Allentown, Bethlehem, Easton, Honey Brook, Oxford, West Chester, 
Kennett Square, Collegeville, Pottstown, Norristown, Lansdale, 
Chalfont, Perkasie, Morrisville, and Doylestown
231 PM EDT Thu Apr 22 2021

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

* WHAT...Sub-freezing temperatures of 29 to 32 expected.

* WHERE...Portions of northern to southern New Jersey and
  eastern Pennsylvania.

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

* IMPACTS...Freeze conditions will kill crops and other sensitive
  vegetation.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take protective measures now as freezing temperatures will damage
or kill tender plants and vegetation. Potted plants should be 
brought inside.

&&

$$

DEZ001-NJZ016>019-PAZ070-071-231000-
/O.NEW.KPHI.FR.Y.0001.210423T0500Z-210423T1300Z/
New Castle-Salem-Gloucester-Camden-Northwestern Burlington-
Delaware-Philadelphia-
Including the cities of Wilmington, Pennsville, Glassboro, 
Camden, Cherry Hill, Moorestown, Mount Holly, Media, 
and Philadelphia
231 PM EDT Thu Apr 22 2021

...FROST ADVISORY IN EFFECT FROM 1 AM TO 9 AM EDT FRIDAY...

* WHAT...Temperatures between 33 and 36 will result in areas of 
  frost formation, mainly away from the Delaware River and outside
  of the urban centers such as Center City Philadelphia and 
  Wilmington.

* WHERE...In New Jersey, Salem, Gloucester, Camden and 
  Northwestern Burlington. In Pennsylvania, Delaware and 
  Philadelphia. In Delaware, New Castle.

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

* IMPACTS...Frost could kill sensitive outdoor vegetation if 
  left uncovered.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold.

&&

$$

DEZ002-003-MDZ012-015-019-020-231000-
/O.NEW.KPHI.FR.Y.0001.210423T0500Z-210423T1300Z/
Kent-Inland Sussex-Kent MD-Queen Annes-Talbot-Caroline-
Including the cities of Dover, Georgetown, Chestertown, 
Centreville, Easton, and Denton
231 PM EDT Thu Apr 22 2021

...FROST ADVISORY IN EFFECT FROM 1 AM TO 9 AM EDT FRIDAY...

* WHAT...Temperatures between 33 and 36 will result in areas of
  frost formation, mainly away from the coasts of Chesapeake Bay
  and Delaware Bay and also outside of the urban centers.

* WHERE...In Maryland, Kent MD, Queen Annes, Talbot and 
  Caroline. In Delaware, Kent and Inland Sussex.

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

* IMPACTS...Frost could kill sensitive outdoor vegetation if 
  left uncovered.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold.

&&

$$

Gorse
2 follow-up statements
664 
WWUS71 KPHI 230802
NPWPHI

URGENT - WEATHER MESSAGE
National Weather Service Mount Holly NJ
402 AM EDT Fri Apr 23 2021

NJZ001-007>010-012-013-015-020>022-027-PAZ060>062-101>106-231300-
/O.CON.KPHI.FZ.W.0004.000000T0000Z-210423T1300Z/
Sussex-Warren-Morris-Hunterdon-Somerset-Middlesex-
Western Monmouth-Mercer-Ocean-Cumberland-Atlantic-
Southeastern Burlington-Berks-Lehigh-Northampton-Western Chester-
Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-
Lower Bucks-
Including the cities of Newton, Washington, Morristown, 
Flemington, Somerville, New Brunswick, Freehold, Trenton, 
Jackson, Millville, Hammonton, Wharton State Forest, Reading, 
Allentown, Bethlehem, Easton, Honey Brook, Oxford, West Chester, 
Kennett Square, Collegeville, Pottstown, Norristown, Lansdale, 
Chalfont, Perkasie, Morrisville, and Doylestown
402 AM EDT Fri Apr 23 2021

...FREEZE WARNING REMAINS IN EFFECT UNTIL 9 AM EDT THIS MORNING...

* WHAT...Sub-freezing temperatures of 29 to 32 expected.

* WHERE...Portions of northern to southern New Jersey and 
  eastern Pennsylvania.

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

* IMPACTS...Freeze conditions will kill crops and other 
  sensitive vegetation.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take protective measures now as freezing temperatures will damage
or kill tender plants and vegetation. Potted plants should be
brought inside.

&&

$$

DEZ001-NJZ016>019-PAZ070-071-231300-
/O.CON.KPHI.FR.Y.0001.000000T0000Z-210423T1300Z/
New Castle-Salem-Gloucester-Camden-Northwestern Burlington-
Delaware-Philadelphia-
Including the cities of Wilmington, Pennsville, Glassboro, 
Camden, Cherry Hill, Moorestown, Mount Holly, Media, 
and Philadelphia
402 AM EDT Fri Apr 23 2021

...FROST ADVISORY REMAINS IN EFFECT UNTIL 9 AM EDT THIS MORNING...

* WHAT...Temperatures between 33 and 36 will result in areas of 
  frost formation, mainly away from the Delaware River and 
  outside of the urban centers such as Center City Philadelphia 
  and Wilmington.

* WHERE...In New Jersey, Salem, Gloucester, Camden and 
  Northwestern Burlington. In Pennsylvania, Delaware and 
  Philadelphia. In Delaware, New Castle.

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

* IMPACTS...Frost could kill sensitive outdoor vegetation if 
  left uncovered.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold.

&&

$$

DEZ002-003-MDZ012-015-019-020-231300-
/O.CON.KPHI.FR.Y.0001.000000T0000Z-210423T1300Z/
Kent-Inland Sussex-Kent MD-Queen Annes-Talbot-Caroline-
Including the cities of Dover, Georgetown, Chestertown, 
Centreville, Easton, and Denton
402 AM EDT Fri Apr 23 2021

...FROST ADVISORY REMAINS IN EFFECT UNTIL 9 AM EDT THIS MORNING...

* WHAT...Temperatures between 33 and 36 will result in areas of 
  frost formation, mainly away from the coasts of Chesapeake Bay 
  and Delaware Bay and also outside of the urban centers.

* WHERE...In Maryland, Kent MD, Queen Annes, Talbot and 
  Caroline. In Delaware, Kent and Inland Sussex.

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

* IMPACTS...Frost could kill sensitive outdoor vegetation if 
  left uncovered.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take steps now to protect tender plants from the cold.

&&

$$
578 
WWUS71 KPHI 231148
NPWPHI

URGENT - WEATHER MESSAGE
National Weather Service Mount Holly NJ
748 AM EDT Fri Apr 23 2021

NJZ001-007>010-012-013-015-020>022-027-PAZ060>062-101>106-231300-
/O.CAN.KPHI.FZ.W.0004.000000T0000Z-210423T1300Z/
Sussex-Warren-Morris-Hunterdon-Somerset-Middlesex-
Western Monmouth-Mercer-Ocean-Cumberland-Atlantic-
Southeastern Burlington-Berks-Lehigh-Northampton-Western Chester-
Eastern Chester-Western Montgomery-Eastern Montgomery-Upper Bucks-
Lower Bucks-
Including the cities of Newton, Washington, Morristown, 
Flemington, Somerville, New Brunswick, Freehold, Trenton, 
Jackson, Millville, Hammonton, Wharton State Forest, Reading, 
Allentown, Bethlehem, Easton, Honey Brook, Oxford, West Chester, 
Kennett Square, Collegeville, Pottstown, Norristown, Lansdale, 
Chalfont, Perkasie, Morrisville, and Doylestown
748 AM EDT Fri Apr 23 2021

...FREEZE WARNING IS CANCELLED...

Temperatures are above freeze and will continue to increase
through the day.

$$

DEZ001>003-MDZ012-015-019-020-NJZ016>019-PAZ070-071-231300-
/O.CAN.KPHI.FR.Y.0001.000000T0000Z-210423T1300Z/
New Castle-Kent-Inland Sussex-Kent MD-Queen Annes-Talbot-Caroline-
Salem-Gloucester-Camden-Northwestern Burlington-Delaware-
Philadelphia-
Including the cities of Wilmington, Dover, Georgetown, 
Chestertown, Centreville, Easton, Denton, Pennsville, Glassboro, 
Camden, Cherry Hill, Moorestown, Mount Holly, Media, 
and Philadelphia
748 AM EDT Fri Apr 23 2021

...FROST ADVISORY IS CANCELLED...

Temperatures are rising to near 40 and will continue to increase 
through the day.

$$

Gorse

The office that day

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

IssuedProductOfficeCountiesLasted
Apr 22, 8:58 AM EDTFreeze WatchPHIAtlantic, Burlington, Cumberland, Hunterdon, Mercer, Middlesex and 6 more6 hr
Apr 22, 2:31 PM EDTFreeze WarningPHIAtlantic, Burlington, Cumberland, Hunterdon, Mercer, Middlesex and 6 more17 hr
Apr 22, 7:32 PM EDTSmall Craft AdvisoryPHI16 hr

Nearby

Frost Advisories in New Jersey, 2021Frost Advisories in Maryland, 2021Frost Advisories in Delaware, 2021Every frost advisory 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.