An area of low pressure and strong upper-level disturbance (vorticity max) may deliver some much needed rainfall across the Washington Region late next week. The image above (courtesy Tropical Tidbits) shows the latest GFS model with a 500-mb vorticity max (dark red colors moving from near St. Louis MO, toward the DC Region) possibly approaching our area Thursday into Friday of next week.
Precipitable Water (measure of the depth of liquid water at the surface that would result after precipitating all of the water vapor in a vertical column over a given location, usually extending from the surface to 300 mb.) will be increasing mid to late next week as a Bermuda high pressure system pumps very moist air into the Mid-Atlantic while a surface low pressure system approaches from the west.
The latest GFS model run from this afternoon shows the potential for some much needed rainfall across the Washington Region Thursday through Friday night (timing subject to change of course).
The latest European 500-mb chart (image above courtesy pivotal weather) shows the unrelenting upper-level high pressure system over the western United States strengthening while a shortwave trough builds into the northeastern corridor late next week. If this forecast verifies, the Mid-Atlantic and New England may be in for another stretch of some cooler weather after we possibly receive some much needed rainfall.