Flash Flood — Montgomery, Pennsylvania

2009-08-02 · near Narberth, Montgomery, Pennsylvania

Event narrative

Thunderstorms with torrential downpours caused flash flooding in several municipalities and a major mudslide across southern Montgomery County. Doppler Radar storm total estimates averaged between 2.5 inches and 4.5 inches.

In Lower Merion Township, a mudslide closed both directions of the Schuylkill Expressway at the Conshohocken Curve from 11 a.m. EDT through 230 p.m. EDT. The westbound lanes were reopened first and the eastbound lanes were reopened at 730 p.m. EDT. Motorists were stranded on the expressway when the mudslide initially occurred. Elsewhere in the township, the Mill Creek flooded and washed out a couple of roads in its basin. There were about a half dozen water rescues. West Mill Creek Park was closed indefinitely. The Mill Creek Pumping Station was under five feet of water. Most roads that were closed were reopened by the 3rd, but River Road was under five feet of water and rocks. In the Wynnewood section, Indian Creek also flooded.

In Upper Dublin Township, flooding occured along the Wissahickon Creek Basin and also included the Rapp and Pine Runs. The Fort Washington Office Park was severely affected and was surrounded by water. Many businesses were flooded and damaged. At least one vehicle was submerged. Ten people were evacuated from one office building. Virginia Drive flooded was severely flooded. The Fort Washington exit ramp off of the Pennsylvania Turnpike and U.S. Route 309 were flooded and closed. A Hilton Inn on West Pennsylvania Avenue was flooded with up to three feet of water on its first floor. It was expected to be closed for a month. Damage to the Industrial Park was estimated at 10 million dollars.

In Whitpain Township, about a dozen residents were asked to evacuate from Maple Street after a culvert flooded. The BoRit asbestos site was damaged as Chestnut Avenue was flooded. In Ambler Borough, several businesses suffered water damage as up to five feet of water accumulated on Main Street. The Butler Pike was closed after a landslide. In Whitemarsh Township, one home had nine feet of water in it. About four streets were flooded. In Springfield Township, the Valley Green Inn was closed for about 24 hours because of Wissahickon Creek flooding.

Event precipitation totals included 5.19 inches in Flourtown, 4.09 inches in Willow Grove, 3.40 inches in Ambler and 2.76 inches in Blue Bell.

Wider weather episode

A warm front that moved northeast in the morning and a cold front that arrived from the west late in the day on the 2nd resulted in numerous showers and thunderstorms across the area with heavy rain and flash flooding. The region was already saturated from all of the heavy rain that fell during the last week of July. Doppler Radar storm total estimates reached as high as 4 to 5 inches across eastern Chester, southern Montgomery and southwestern Bucks Counties and caused flash flooding. Doppler Radar storm total estimates also exceeded 3 inches in parts of western and southern Berks County. Because of the flooding, Pennsylvania Governor Ed Rendell requested and received approval from the United States Small Business Administration to have disaster area declaration for Berks, Bucks, Chester, Delaware, Lehigh, Montgomery and Philadelphia Counties.

View location on OpenStreetMap → (40.0239, -75.2821)

Source: NOAA Storm Events Database, event_id 193356. Narrative written by the NWS forecast office that issued the report.