Alert archive / Pennsylvania / Flash Flood Warnings in 2023

Flash Flood Warning 1, NWS Philadelphia/Mount Holly

April 15, 2023Lehigh County, Northampton County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Apr 15, 2023, 1:22 PM EDT for Lehigh County, Northampton County, Pennsylvania. It was in force for 4 hr. 2 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Apr 15, 2023, 1:22 PM EDT (17:22 UTC)
Expired: Apr 15, 2023, 5:30 PM EDT
In force: 4 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

Counties Lehigh County, PA, Northampton County, PA

The radar

The Philadelphia radar (KDIX), 115 km from the middle of the area, began a volume at 17:26 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 was reported inside it

Time	Report	Where	Remark
Apr 15, 1:30 PM EDT	FLASH FLOOD	1 Nw Upper Saucon Twp, PA	US ROUTE 309 IS CLOSED AT HUCKLEBERRY DRIVE.
Apr 15, 2:00 PM EDT	FLASH FLOOD	Fountain Hill, PA	ROADWAY FLOODING.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Brookhaven, NY (KOKX), launched 12:00Z, 5.4 hours before the alert went out and 219 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 26 J/kg
Mixed-layer CIN: -187 J/kg
Mixed-layer LCL: 927 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: -16 m²/s²
0-3 km storm-relative helicity: 26 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

851 
WGUS51 KPHI 151722
FFWPHI
PAC077-095-152130-
/O.NEW.KPHI.FF.W.0001.230415T1722Z-230415T2130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Mount Holly NJ
122 PM EDT Sat Apr 15 2023

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Eastern Lehigh County in eastern Pennsylvania...
  Central Northampton County in eastern Pennsylvania...

* Until 530 PM EDT.

* At 122 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 2.5 inches of 
  rain have fallen. Additional rainfall amounts of 1 to 2 inches are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flooding of small creeks and streams, urban areas,
           highways, streets, and underpasses as well as other
           drainage and low lying areas.

* Some locations that may experience flash flooding include...
  Allentown, Bethlehem, Emmaus, Northampton, Hellertown, Nazareth, 
  Bath, Steuben, Lehigh University, Beersville, Danielsville, and 
  Zionsville.

This includes the following highways...
	Interstate 78 in Pennsylvania between mile markers 56 and 69.
	Northeast Extension between mile markers 46 and 53.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most 
flood deaths occur in vehicles.

&&

LAT...LON 4080 7554 4083 7529 4056 7530 4049 7541
      4042 7549 4045 7553

FLASH FLOOD...RADAR INDICATED

$$

Fitzsimmons

1 follow-up statement

564 
WGUS71 KPHI 151855
FFSPHI

Flash Flood Statement
National Weather Service Mount Holly NJ
255 PM EDT Sat Apr 15 2023

PAC077-095-152130-
/O.CON.KPHI.FF.W.0001.000000T0000Z-230415T2130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Lehigh PA-Northampton PA-
255 PM EDT Sat Apr 15 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 530 PM EDT THIS 
AFTERNOON FOR EASTERN LEHIGH AND CENTRAL NORTHAMPTON COUNTIES...

At 255 PM EDT, doppler radar indicated thunderstorms producing heavy 
rain with upwards of 2 to 2.5 inches of rain having already fallen. 
Emergency management also reported US Route 309 is closed at 
Huckleberry Drive in Upper Saucon Township due to flash flooding.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Emergency management reported.

IMPACT...Flooding of small creeks and streams, urban areas,
         highways, streets, and underpasses as well as other
         drainage and low lying areas.

Some locations that may experience flash flooding include...
  Allentown, Bethlehem, Emmaus, Northampton, Hellertown, Nazareth, 
  Bath, Steuben, Lehigh University, Beersville, Danielsville, and 
  Zionsville.

This includes the following highways...
	Interstate 78 in Pennsylvania between mile markers 56 and 69.
	Northeast Extension between mile markers 46 and 53.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around...don't drown when encountering flooded roads. Most 
flood deaths occur in vehicles.

&&

LAT...LON 4080 7554 4083 7529 4056 7530 4049 7541
      4042 7549 4045 7553

FLASH FLOOD...OBSERVED

$$

Fitzsimmons

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 15, 12:42 PM EDT	Special Weather Statement	PHI	Northampton	48 min
Apr 15, 1:03 PM EDT	Severe Thunderstorm Warning	PHI	Carbon, Lehigh, Monroe, Northampton	27 min
Apr 15, 1:34 PM EDT	Severe Thunderstorm Warning	PHI	Monroe, Northampton	26 min
Apr 15, 1:51 PM EDT	Severe Thunderstorm Warning	PHI	Chester	24 min
Apr 15, 1:58 PM EDT	Severe Thunderstorm Warning	PHI	Monroe, Northampton	32 min
Apr 15, 2:02 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Lehigh, Northampton	28 min
Apr 15, 2:17 PM EDT	Areal Flood Advisory	PHI	Chester	3 hr
Apr 15, 4:05 PM EDT	Severe Thunderstorm Warning	PHI	Bucks, Philadelphia	25 min
Apr 15, 4:56 PM EDT	Severe Thunderstorm Warning	PHI	Bucks	14 min
Apr 15, 5:20 PM EDT	Flash Flood Warning	PHI	Lehigh	3 hr
Apr 15, 6:05 PM EDT	Areal Flood Advisory	PHI	Bucks	96 min

Nearby

Flash Flood Warnings in Pennsylvania, 2023 Every flash flood warning in 2023

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.