Alert archive / Pennsylvania / Flash Flood Warnings in 2023

Flash Flood Warning 3, NWS Philadelphia/Mount Holly

April 15, 2023Lehigh County, Pennsylvania

NWS Philadelphia/Mount Holly issued this flash flood warning at Apr 15, 2023, 5:20 PM EDT for Lehigh County, Pennsylvania. It was in force for 3 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, 5:20 PM EDT (21:20 UTC)
Expired: Apr 15, 2023, 8:01 PM EDT
In force: 3 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon
Flood severity: None

County Lehigh County, PA

The radar

The Philadelphia radar (KDIX), 123 km from the middle of the area, began a volume at 21:20 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, 5:31 PM EDT	FLASH FLOOD	1 Ssw Ancient Oaks, PA	REPORT FROM MPING: STREET/ROAD FLOODING; STREET/ROAD CLOSED; VEHICLES STRANDED.
Apr 15, 6:00 PM EDT	HEAVY RAIN 3.45	1 Ssw Ancient Oaks, PA	TIME ESTIMATED.

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

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 9.3 hours before the alert went out and 234 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: 497 J/kg
Mixed-layer CIN: -52 J/kg
Mixed-layer LCL: 598 m above ground
0-6 km bulk shear: 19 kt
0-1 km storm-relative helicity: -14 m²/s²
0-3 km storm-relative helicity: 19 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

071 
WGUS51 KPHI 152120
FFWPHI
PAC077-160130-
/O.NEW.KPHI.FF.W.0003.230415T2120Z-230416T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Mount Holly has issued a

* Flash Flood Warning for...
  Lehigh County in eastern Pennsylvania...

* Until 930 PM EDT.

* At 520 PM EDT, a trained weather spotter reported a water rescue 
  due to flash flooding in Trexlertown. Between 1.5 and 2 inches of 
  rain have fallen. Flash flooding is already occurring.

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Trained spotters 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, Emmaus, Ancient Oaks, Coffeetown, Claussville, 
  Zionsville, Schnecksville, Coplay, Macungie, Coopersburg, 
  Alburtis, and Fullerton.

This includes the following highways...
	Interstate 78 in Pennsylvania between mile markers 45 and 63.
	Northeast Extension between mile markers 47 and 64.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Motorists should not attempt to drive around barricades or drive 
cars through flooded areas.

&&

LAT...LON 4060 7577 4067 7571 4070 7552 4063 7548
      4054 7535 4043 7551 4045 7553 4048 7558
      4049 7560 4050 7561 4050 7562 4052 7564
      4053 7566 4054 7567 4055 7570 4058 7574
      4059 7575

FLASH FLOOD...OBSERVED

$$

Fitzsimmons

1 follow-up statement

760 
WGUS71 KPHI 160001
FFSPHI

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

PAC077-160011-
/O.CAN.KPHI.FF.W.0003.000000T0000Z-230416T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Lehigh PA-
801 PM EDT Sat Apr 15 2023

...FLASH FLOOD WARNING IS CANCELLED FOR LEHIGH COUNTY...

Flood waters are receding. The heavy rain has ended. Flooding is no 
longer expected to pose a threat.

LAT...LON 4060 7577 4067 7571 4070 7552 4063 7548
      4054 7535 4043 7551 4045 7553 4048 7558
      4049 7560 4050 7561 4050 7562 4052 7564
      4053 7566 4054 7567 4055 7570 4058 7574
      4059 7575

$$

Iovino

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, 1:22 PM EDT	Flash Flood Warning	PHI	Lehigh, Northampton	4 hr
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, 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.