Flash Flooding in Pennsylvania, March 21, 2002

Name: Flash Flooding in Pennsylvania, March 21, 2002
Start: 2002-03-21T06:00
End: 2002-03-21T10:00
Location: Pennsylvania

March 21, 2002 · NWS PBZ · 2 events in 2 counties and zones

50 inches across the Monongahela River basin resulted in minor flooding on the Monongahela River in southwest Pennsylvania. 0 feet).

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.

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

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $10,000
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 PBZ wrote it up.

Heavy rains of 1.00 to 2.50 inches across the Monongahela River basin resulted in minor flooding on the Monongahela River in southwest Pennsylvania. The Monongahela River crested at Charleroi at 28.1 feet (flood stage 28.0 feet) at 7 AM on March 21st, while just a bit further upstream at Elizabeth, the river crested at 7:30 AM on March 21st at 20.2 feet (flood stage 20.0 feet).

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 Pittsburgh, PA wrote its last area forecast discussion before the first event at Mar 21, 4:15 AM EST, 1 hour 45 minutes earlier.

Area forecast discussion, Mar 21, 4:15 AM EST, 1 hour 45 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
415 AM EST THU MAR 21 2002

MODELS CONTINUE TO SHOW A SECONDARY COLD FRONT MOVING THROUGH THE
UPPER OHIO VALLEY THIS AFTERNOON...GIVING A 50-60 PERCENT CHANCE OF
RAIN SHOWERS. WITH TEMPERATURES QUICKLY PLUMMETING THROUGH THE 30S
THIS EVENING...AND UNSTABLE LOWLEVEL FLOW FROM THE
NORTHWEST...SCATTERED LAKE EFFECT SNOW SHOWERS WILL MOVE ACROSS THE
REGION TONIGHT. MOST LOCATIONS WILL GET AN INCH OR LESS...BUT
ACCUMULATIONS OF 2-3 INCHES CAN OCCUR NEAR I-80 AND THE RIDGES. BY
FRIDAY...ONLY FLURRIES EXPECTED SOUTH...BUT SCATTERED LIGHT SNOW
SHOWERS STILL POSSIBLE NORTH AND RIDGES.

AS FLOW ALOFT TURNS FROM NORTHWEST TO WEST THIS WEEKEND...THE COLD
OUTBREAK WILL WANE UNDER THE MARCH SUN. HOWEVER SOUTHWEST WINDS
EMERGING FROM THE GULF MAY YIELD ENOUGH ISENTROPIC/WARM FRONTAL/LIFT
TO GIVE A CHANCE OF PRECIPITATION SUNDAY. TYPE WILL BE GIVEN AS BOTH
SNOW AND RAIN...PARTICULARLY NORTH...CONSIDERING BOUNDARY LAYER
TEMPERATURES. AVN SHOWS PRECIPITATION...MAINLY RAIN...SHOULD
CONTINUE INTO MONDAY AND POSSIBLY TUESDAY...AS A LONG WAVE TROUGH
RE-ESTABLISHES ITS POSITION OVER THE ROCKIES.

TEMPERATURES ADJUSTED PER LATEST GUIDANCE...INCLUDING NEW MRF MOS.

.PBZ...

MD...NONE.
OH...NONE.
PA...RIVER FLOOD WARNING TONIGHT AND THURSDAY PAZ021-029-030-031-032.
WV...NONE.

The radar

The Pittsburgh radar (KPBZ), 38 km away, was scanning. The volume nearest the first event began at 10:59 UTC.

Open the radar archive at this moment

Event by event

2 flash flood. Local standard time, as filed.

Flash Flood, Washington

When: March 21, 6:00 AM EST to 9:00 AM EST
Where: Washington County, Charleroi
Property damage: $5,000
Reported by: OFFICIAL NWS OBS.
Coordinates: 40.189, -80.248 (the zone’s center; the record gives no point)

Flash Flood, Allegheny

When: March 21, 6:00 AM EST to 10:00 AM EST
Where: Allegheny County, Elizabeth
Property damage: $5,000
Reported by: OFFICIAL NWS OBS.
Coordinates: 40.469, -79.981 (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

Every storm in Pennsylvania in 2002 Every state in 2002 This day in weather history Warnings in Pennsylvania, March 2002

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: 5286810, 5286904.