What has changed

No major changes were made to the forecast this afternoon.

Messages

1) Slight chance for a shower or storm this afternoon, then dry conditions anticipated through early portions of the week.

2) Warmer and more humid conditions return mid-week, with thunderstorm chances returning by Thursday.

Discussion

KEY MESSAGE 1. Slight chance for a shower or storm this afternoon, then dry conditions anticipated through early portions of the week.

A closed upper low continues to circulate over the Great Lakes this afternoon, with broader troughing extending outward across most of the eastern CONUS. An associated surface low is located just downstream of the upper low near the Ontario/Quebec border. A cold front attendant to this low has progressed off the Mid-Atlantic coastline, with drier air starting to filter in from the west. Dewpoints have dropped into the 50s and lower 60s behind the front, with temperatures climbing into the upper 70s to mid 80s beneath mostly sunny skies. A few fair weather cumulus have developed in response to daytime heating and resultant mixing. Some CAM solutions show a few showers or storms forming over the next few hours, especially to the east of the Blue Ridge, but most locations should remain dry. Any storms that do form will likely be very short- lived. If a deeper storm were to develop, there could be a conditional threat for some small hail, given cooler, drier thermal profiles, minimal storm energy below the freezing level, and straight line hodographs with very little low- level shear, but respectable shear (around 35-40 knots 0-6 km) through the mid- upper levels. Any showers or storms should quickly dissipate with loss of daytime heating this evening.

High pressure will continue to slowly build toward the area on Monday and Tuesday, resulting in dry conditions and lower humidity levels. High temperatures will generally be in the upper 70s to mid 80s, with overnight lows in the 50s to lower 60s.

KEY MESSAGE 2. Warmer and more humid conditions return mid- week, with thunderstorm chances returning by Thursday.

Heading into Wednesday, dry, pleasant conditions continue into much of the day and afternoon. As an upper level ridge over the midwest begins to flatten in amplitude, southwesterly mid-level winds advect tropical moisture northward into our region. As this tropical air mass moves through our region, humid conditions return through the end of the week.

Temperatures rise back into late-August normals with highs in the 80s and 90s Thursday with models depicting a cold front draping north to south across the Mid-Atlantic. As an upper- level low near Hudson Bay pushes this front across our region, chances for showers and thunderstorms return and could linger into the weekend. Best chances for stronger storms are Thursday and Friday depending on the timing of a short wave deepening an upper- level low over Ontario Canada.