Pennsylvania, 2001

Flash Flooding in Pennsylvania, July 26, 2001

July 26, 2001 · NWS PHI · 2 events in 1 county or zone

Thunderstorms with heavy rain over extreme northern Montgomery County during the evening of the 25th and runoff from the thunderstorms that same evening over Berks County led to the flooding of two streams in Montgomery County on the 26th. m.

Where it happened

Every event with a place to put it; 2 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

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  • Tropical storms and surge
  • Floods
  • Wind
  • Hail
  • Winter weather
  • Heat and drought
  • Cold
  • Fire, smoke and dust
  • Marine and coastal
  • Other

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The toll

Deaths
0
Injuries
0
Property damage
None recorded
Crop damage
None recorded
Events
2

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS PHI wrote it up.

Thunderstorms with heavy rain over extreme northern Montgomery County during the evening of the 25th and runoff from the thunderstorms that same evening over Berks County led to the flooding of two streams in Montgomery County on the 26th. The West Branch of the Perkiomen Creek and East Greenville was above its 5 foot flood stage from 108 a.m EDT through 341 a.m. EDT. It crested at 5.48 feet at 230 a.m. EDT. The Manatawny Creek at Pottstown was above its 6 foot flood stage from 625 a.m. EDT through 934 a.m. EDT on the 26th. It crested at 6.67 feet at 815 a.m. EDT. Doppler Radar storm total estimates reached 3 inches in extreme northern Montgomery County.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Jul 25, 7:50 PM EST, 4 hours 18 minutes earlier.

Area forecast discussion, Jul 25, 7:50 PM EST, 4 hours 18 minutes before
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
850 PM EDT WED JUL 25 2001

HAVE ISSUED FLASH FLOOD WATCH FOR NRN HALF OF CWA...MOST OF OUR ERN
PA COUNTIES AND NRN HALF OF OUR NJ COUNTIES...AS SVRL FACTORS ARE
COMING TOGETHER TO AT LEAST PROVIDE THE POTL FOR FLSH FLDG WHICH OF
COURSE ALREADY OCCURRED IN MONROE COUNTY PA EARLIER. HOWEVER... WITH
HI PWATS ACTIVATED BY MDT INSTABY FOCUSING ON THE QSNTRY FNTL BNDRY
FM ECNTRL PA TO NRN NJ...FEEL THAT FLASH FLOODING MAY BCM MORE OF A
PBLM OVRNGT. VIGOROUS CONVERGENCE IS NOTED IN THE EWD MOVG CURRENT
ACTIVITY CONTRASTING WITH THE NWD MOVG CONVTN TO OUR SOUTH. WITH
MESO-MODELS SHOWING FNT LINGERING IN OUR NRN ZONES INTO THU
MRNG...AND WITH CLIMATOLOGICALLY FAVORED MONTHLY AND DIURNAL
TIMING...FEEL THAT A WATCH IS JUSTIFIED.

REST AS FM PREVIOUS...

****************************************************************

HEAT WAVE/SOUPY AIRMASS WANING AS COLD FRONT APPROACHES FROM THE
NORTHWEST. QUITE UNSTABLE SOUTH OF THE FRONT THIS AFTERNOON WITH
LI/S APPROACHING -6 C AND CAPES 2500 J/KG. PRECIPITABLE H20 RUNNING
HIGH AROUND 2.00 INCHES. THE MORNING SOUNDING OUT OF KPIT VERIFIES
THIS. HEAT INDICES RUNNING AROUND 100 DEGS ATTM AND WILL ALLOW HEAT
WARNING TO EXPIRE AT 800 PM THIS EVENING.

WEAK WAVES WITH MINOR SURFACE REFLECTION TO MOVE ALONG FRONT THE
NEXT 24 HOURS. ALTHOUGH SURFACE REFLECTIONS ARE MINOR...LOW LEVEL
CONVERGENCE WILL INCREASE. THIS COMBINED WITH THE HIGH PW/S WILL
HELP INDUCE PERIODS OF INTENSE RAINFALL FOR THE CWA STARTING TONIGHT
AND CONTINUING TOMORROW.

SLOW MOVING COLD FRONT SAGS SOUTH OF CWA BEHIND SECOND WEAK WAVE
THURSDAY NIGHT. WILL END PRECIP ACROSS THE NORTH AT THIS TIME...BUT
CONTINUE ACROSS THE SOUTHERN CWA INTO EARLY 4TH PERIOD.

AFTER FROPA...GRIDDED H8 TEMPS DROP A GOOD 5 TO 9 DEGS C WITH
NORTHERN AREAS BOTTOMING OUT NEAR 9 DEGS C. THIS WILL HELP PUSH
TEMPERATURES BACK INTO THE 70S AND LOWER 80S THURSDAY AND FRIDAY.

THE EXTENDED PORTION WILL INDICATE A CHANGE FOR SATURDAY WITH
SHOWERS AND THUNDERSTORMS POSSIBLE ACROSS THE SOUTH AS ABOVE
MENTIONED COLD FRONT SITS JUST TO OUR SOUTH. WITH RETURN FLOW
AFFECTING THE CWA SUNDAY AND MONDAY WILL KEEP POPS GOING. REST OF
EXTENDED WILL BE DRY.

KRUDZLO

****************************************************************

.PHI...
DE...SMALL CRAFT ADVISORY COAxST.
MD...NONE.
NJ...FLASH FLOOD WATCH TONIGHT NJZ001-007>010-0120015.
     ...SMALL CRAFT ADVISORY COAST.
PA...FLASH FLOOD WATCH TONIGHT PAZ054-055-060>062-067>069.

In the hours before

Local storm report, Jul 25, 6:41 PM EST, 5 hours 27 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY, NJ
741 PM EDT WED JUL 25 2001

TIME(EDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0600 PM    EASTON                    PA   WIND DAMAGE
07/25/01   NORTHAMPTON                    TREES DOWN

0655 PM    UPPER SAUCON TOWNSHIP     PA   WIND DAMAGE
07/25/01   LEHIGH                         LARGE BRANCHES DOWN

The radar

The Philadelphia radar (KDIX), 86 km away, was scanning. The volume nearest the first event began at 05:10 UTC.

Open the radar archive at this moment

Event by event

2 flash flood. Local standard time, as filed.

Flash Flood, Montgomery

When
July 26, 12:08 AM EST to 2:41 AM EST
Where
Montgomery County, North Portion
Reported by
AWOS,ASOS,MESONET,ETC
Coordinates
40.211, -75.367 (the zone’s center; the record gives no point)

Flash Flood, Montgomery

When
July 26, 5:25 AM EST to 8:34 AM EST
Where
Montgomery County, North Portion
Reported by
AWOS,ASOS,MESONET,ETC
Coordinates
40.211, -75.367 (the zone’s center; the record gives no point)

What these are

Flash Flood
Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Pennsylvania in 2001Every state in 2001This day in weather historyWarnings in Pennsylvania, July 2001

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5260501, 5260502.