Sunset behind the George Washington Masonic Temple in Alexandria, Virginia; photo by Dyoshida
Humidity will become noticeably higher Tuesday afternoon as south-south-easterly flow at the surface begins to pump juicy dew points in the lower 70s into the Washington Area.
Highs Monday and Tuesday will soar into the lower to middle 90s with heat indexes approaching 100 degrees on Monday.
Tuesday will be the most miserable day of the work week (it will feel like the Deep South around here) with temperatures in the 90s and dew points in the 70s. Heat indexes could potentially eclipse 105 degrees and a heat advisory may be needed during the afternoon hours (the image below, courtesy pivotal weather shows dew points of 70 degrees or greater in purple Tuesday through Wednesday evening).
A “back door cold front” will move in from the northeast on Wednesday acting as a surface trigger for numerous showers and thunderstorms. This cold front will push south and west of the Washington Area becoming stalled out across the Appalachians through Friday before working back northward through DC as a warm front on Friday. The image below courtesy pivotal weather shows showers and thunderstorms developing Wednesday afternoon across the DC Region.
You can see the North American Model picking up this back door cold front by watching the dew points in the image below. Notice the dryer dew points moving southwest from the Delaware and New Jersey coastline as the marine layer begins to push into our area Wednesday evening.
Scattered showers and thunderstorms will again be possible each day Thursday through the upcoming weekend.