This evening, the relentless, multi-day heat wave is finally beginning to lose its grip on our region. While it hasn’t been quite as brutal as the last 48 hours, the combination of high temperatures and thick humidity still pushed the heat index up to a stifling 105 to 106 degrees this afternoon. A Heat Advisory remains in effect for the majority of our area until 8:00 PM tonight.

If you are lucky, a pop-up shower or thunderstorm might provide some quick relief and knock temperatures down over the next few hours. However, the true weather story is shifting rapidly from extreme heat to a significant flooding and storm threat as we head into Monday.

Here is what you need to know to prepare for the start of the workweek.

Monday’s Threat: Searing Heat Swaps for Heavy Rain & Flash Flooding

The Weather Prediction Center (WPC) has expanded its Slight Risk (Level 2 of 4) for excessive rainfall to cover almost our entire area on Monday.

As a weak upper-level trough edges closer to us, a stagnant, incredibly moisture-rich airmass will settle over the region. Precipitable Water (PWAT) values—a metric meteorologists use to measure the total amount of water vapor available in the atmosphere—are expected to spike over 2.0 inches. That is roughly 150% of what is normal for early July.

What this means for your Monday commute and afternoon:

• Widespread Storms: Atmospheric models are in strong agreement that widespread thunderstorm development will begin by early Monday afternoon, starting inland and moving toward the coast by evening.
• Torrential Downpours: These storms will be highly efficient rainfall producers and very slow-moving. High-resolution models highlight a 30% chance that some locations could see a blistering 3 inches of rain in just a 3-hour window, with localized totals reaching 3 to 4 inches.
• Flash Flooding: Because the ground is baked and the rainfall rates will be intense, flash flooding is a distinct possibility, particularly in urban, low-lying, and flood-prone areas. A Flood Watch may be issued tonight or early tomorrow morning.

In addition to the rain, the Storm Prediction Center (SPC) has placed the area under a Marginal Risk (Level 1 of 5) for severe weather. A few isolated storms could easily produce damaging wind gusts and frequent, dangerous lightning.

The Silver Lining: A Return to Seasonal Norms

If there is a bright spot in this transition, it is that the intense cloud cover and widespread rain will put a definitive end to our heat headlines.

A weak cold front is slated to cross the area on Wednesday, which promises to give us our coolest day of the week, with afternoon highs potentially staying in the mid-to-upper 80s.

Local Travel & Marine Notes

Marine: While general boating conditions remain below Severe Weather Advisory thresholds, local mariners should keep a close eye on the radar. Strong thunderstorms over the Chesapeake Bay and local rivers could produce sudden, dangerous wind gusts up to 20 knots or higher on both Sunday and Monday evenings.

Equipment Note: Keep in mind that the local KAKQ radar is currently down due to mechanical issues with no estimated return time, so utilize surrounding regional radars or composite loops to track incoming storms.

Stay weather-aware tomorrow, ensure you have a way to receive flash flood warnings, and never drive through flooded roadways.