Why Today’s Storms Could Be So Wet: Understanding Precipitable Water

Published August 1, 2025 – Rowan County Weather

One of the most important ingredients driving today’s risk for heavy rain and flash flooding in Rowan County is something called "precipitable water." While the term might sound technical, the impact is very real—especially when thunderstorms are involved.

What Is Precipitable Water?

Precipitable water (often abbreviated as PWAT on weather maps) is a measure of how much water vapor is in the entire column of air above a given location. If you could condense all that moisture and wring it out like a sponge, precipitable water tells you how much rainfall you'd get.

On a typical summer day, precipitable water values around 1.5 inches are common across the Carolinas. Today, however, values over Rowan County are pushing 2 inches—well above normal. This signals that the atmosphere is holding a much higher amount of moisture than usual.

Why It Matters Today

When you combine high precipitable water with slow-moving thunderstorms or storms that repeatedly track over the same area, you increase the risk for very heavy rainfall in a short period of time. That can overwhelm drainage systems, especially in urban areas, and lead to flash flooding.

Here’s what’s contributing to the elevated flood threat today:

• A stalled frontal boundary is slowly drifting through the region

• The air mass is extremely moist, with PWAT values near 2 inches

• Storms are expected to develop this afternoon and evening, potentially clustering or training over the same spots

These factors have prompted the Weather Prediction Center to issue a Slight Risk (Level 2 of 4) for excessive rainfall across Rowan County, meaning isolated flash flooding is possible.

The Local Impacts

While not every storm will produce flooding, the ones that do could do so quickly. Urban areas such as downtown Salisbury, Spencer, and other parts of the county with poor drainage are most at risk, along with any areas that have already received significant rainfall this week.

Even if you’re not in a flood-prone zone, strong downpours could temporarily reduce visibility and create ponding on roadways.

What to Watch For

• Keep an eye on the radar this afternoon between 2 PM and 9 PM

• If a Flash Flood Warning is issued, move to higher ground and never drive across flooded roads

• Expect storms to be capable of producing 1 to 2 inches of rain per hour, locally higher in stronger cells

Looking Ahead

A wedge of cooler and drier air is on the way for the weekend, bringing a welcome drop in humidity and highs in the 70s. But first, Rowan County has to get through one last round of hot and humid weather with a chance for storms that could soak parts of the region.

As always, stay tuned to Rowan County Weather for real-time updates.