Update: Flood Watch Issued in Thursday ‘Firehose’ Rain

MOUNT HOLLY NJ – Hazardous weather outlook and flash flood watch notices for western Montgomery County, and specifically for the boroughs of Pottstown and Collegeville, were issued Wednesday (Sept. 22, 2021) at 3:24 a.m. by the National Weather Service office in Mount Holly NJ in anticipation of a storm now expected Thursday afternoon through Friday morning (Sept. 23-24).

The weather service said “showers and thunderstorms will develop ahead of, and with, the passage of a cold front Thursday afternoon through late Thursday night. Rain will be heavy at times. Widespread rainfall totals will range from 2 to 3 inches, with locally higher amounts.”

“Flash flooding is possible during this time,” it added. It suggested area residents “monitor later forecasts and be prepared to take action should flash flood warnings be issued.”

Read a story about earlier predictions for this week’s storm, published Tuesday (Sept. 21) by The Post, below:

Slow Storm May Bring ‘Firehose’ Rain this Week

STATE COLLEGE PA – A slow-moving storm that will creep eastward Tuesday through Thursday (Sept. 21-23, 2021) from near Chicago and St. Louis toward the East Coast is expected to create occasional “firehose effect” downpours in Southeastern Pennsylvania later during the week, forecasters with AccuWeather Inc. reported.

Developing low pressure is anticipated to slow down the storm front, as an area of high pressure off the coast creates what AccuWeather described as “an atmospheric roadblock.” It means rain could last longer in any one location – opening the firehose, so to speak – and pose potential flood threats due to rain duration and intensity.

An AccuWeather map (at top) shows how locally severe thunderstorms from Wednesday until Thursday night, at their peak occasionally producing 1-2 inches of rain per hour, may result in flash flooding that could delay traffic and disrupt travel plans. AccuWeather’s Alex Sosnowski said local amounts may climb to 4 inches in the mid-Atlantic region.

Rainfall of this magnitude is not only likely to trigger rapid flooding in urban areas, but very fast rises in water levels can occur along small streams and some of the rivers in the region. AccuWeather forecasters reminded drivers to heed the adage “turn around, don’t drown,” and never drive through floodwaters.

Weather map graphic supplied by AccuWeather Inc.