A powerful cold front will abruptly end a summerlike Friday with a brief but potentially intense line of gusty showers and thunderstorms. Temperatures will tumble and winds will howl after the front passes, setting the stage for a blustery Saturday and frosty start to Sunday.
The showers and storms will probably arrive between 5 and 9 p.m. Friday as a squall line, first sweeping through our far western suburbs before reaching the Beltway area between 6 and 8 p.m. The narrow line will move through quickly — with storms lasting 30 minutes or less in most spots — but could pack a punch.
The National Weather Service has issued a severe thunderstorm watch for the entire DC region until 8 p.m. Generally, storms are expected to become more intense farther north.
The main hazard will be damaging wind gusts, which could arrive suddenly. Peak gusts could reach 50 to 65 mph, strong enough to bring down trees and cause isolated to scattered power outages.
(National Weather Service)
After the squall line passes, a few additional showers could develop overnight, mainly east of Interstate 95. But the bigger story will be the dramatic drop in temperatures.
Following highs near 80 Friday afternoon, temperatures will plunge through the 70s and 60s as the squall line sweeps through. By dawn Saturday, lows will fall to around 50. In other words, most areas will experience a roughly 30-degree temperature drop in just 12 hours.
Winds will also crank up, with gusts of 20 to 30 mph beginning late Friday night and continuing through much of Saturday. Temperatures will struggle to recover amid the blustery conditions, with highs only reaching the mid-50s — over 25 degrees cooler than Friday.
Frost possible Sunday morning west of Interstate 95
As winds ease under clear skies Saturday night, temperatures will fall to their lowest levels of the season, bringing a risk of frost to colder areas.
Lows are expected to dip into the mid- to upper 30s in most areas, except for the low 40s in downtown Washington and near the Potomac River and Chesapeake Bay.
Patchy frost is possible in colder locations west of Interstate 95, especially in sheltered valleys and other low-lying areas.
Jeff Halverson contributed to this report.