Baltimore and Washington DC are bracing for a day of sweltering heat and the threat of severe thunderstorms, as reported by the National Weather Service (NWS). The forecast, published early this morning, has residents eyeing the skies and thermometers, with the mercury expected to reach the mid to upper 90s. Humidity is stacking the odds for discomfort and the atmosphere is primed for tumult. This includes damaging winds, large hail, and isolated instances of flooding due to high precipitable water values of around 1.5 inches, where urban and poor drainage areas are most vulnerable. National Weather Service has noted, "Isolated instances of urban and poor drainage flooding are also possible given increased PWAT values around 1.5 inches."

The cold front from the Ohio River Valley is the main attraction, slated to sweep across the region late this afternoon into early Thursday morning. After passing the cold front, relief is somewhat in sight, with dropped temperatures and drier air trailing behind it. However, the heat is loitering just around the corner, with another heated wave foreshadowed for the weekend. "Ahead of the front, south to southwesterly flow will help boost afternoon temperatures into the mid to upper 90s," states the National Weather Service. However, they've also mentioned that the extent of this heat could be tempered by morning cloud cover.

Thursday and Friday will see a mild reprieve as high pressure sneaks in from the north and west. Despite a dip in the temps, the specter of showers around the Shenandoah Valley and Virginia Piedmont could still be looming come Friday evening. Airports in the region, meanwhile, are preparing for potential disruptions with VFR conditions expected to degrade as the thunderstorms roll in. The forecast calls for conditions to stabilize briefly through Thursday night before the cycle renews with shower possibilities on Friday.

Looking toward the weekend, the expectation is a sultry outlook with temperatures predicted to hop back into the low 90s. The integrated heat and moisture may shove conditions dangerously close to Heat Advisory thresholds. With thunderstorm threats increasing in this unstable atmosphere, "Heat indices into the 100 to 105-degree range." could become a stark reality, warns the National Weather Service, emphasizing the perils of excessive heat returning mid-week.

The marine front is also under a weather siege with the potential for strong to severe thunderstorms leading to choppy conditions and advisories. This includes the Chesapeake Bay and tidal Potomac, where the Small Craft Advisory is a reflection apprehensive of the impending weather onslaught predicted to start around 21z. Boaters are being urged to stay vigilant as the waters might turn aggressive, coinciding with the frontline's arc bringing with it vigorous winds and rain.

Switching gears to tides and coastal flooding, there's an air of cautious optimism. While water levels spiked up to about 1.25 feet over normal due to southerly winds, the immediate risk of flooding appears slim. The impending cold front should help draw down the tides, with "a cold frontal passage tonight should help lower the tides into Thursday." as reported by the National Weather Service. It seems that, for now, the waterfront communities might evade the fingers of flooding.

Climate records are flirting with breaking points amidst this heated episode, with Wednesday's high temperatures threatening to shatter previous benchmarks. Indeed, if the forecast holds, Washington-National (DCA) could see the temperature gauges push into the upper brackets of the 90s, approaching the historical 101F set in 1952.