June Rainfall: 1.65″ (165 percent of normal)
June Temp Dep: -3.0
Rainfall since May 9: 3.41″ (82 percent of normal)
A frontal zone separating hot summery air from cooler Atlantic air will stretch from eastern Ontario to just east of the Delaware River. Moisture converging across the frontal zone will bring patchy clouds and a few scattered mainly afternoon thunderstorms north of the city.
A large high pressure system over southeastern Canada will drift south to the Gulf of Maine by Monday morning. On Monday, the clockwise easterly flow around the high will push this frontal zone west of the city to near the Appalachians.
As a result, Monday will be a bit cooler as the easterly flow drives ocean cooled air into the region. A cold front extending from the Great Lakes to Oklahoma late on Monday will approach the Eastern Seaboard Monday night and Tuesday.
A southerly flow ahead of the front will draw an area of showers (associated with a disturbance) north from the Gulf of Mexico. The disturbance will interact with the front and produce a corridor of showers and thunderstorms from the interior South to the interior Northeast Monday night.
This corridor of showers and storms will approach the Northeast Seaboard on Tuesday as high pressure retreats into the Atlantic. Rain, perhaps accompanied by a rumble of thunder, will arrive late in the day on Tuesday toward evening and continue overnight. The showers will linger into early Wednesday as a large vortex over east-central Atlantic slows the eastward progress of the front. Some rain will be heavy with totals of 1-1.5″ expected.
On Thursday, a compact area of low pressure should form on this frontal zone near the mid-Atlantic coast. The low will maintain the threat of showers, especially east of the city. The low pressure zone will pull well east of the area late in the week, however, considerable clouds and the risk for a few passing showers will persist as breezes from the east import moist air from the Atlantic inland. These onshore winds will keep temperatures a bit below normal.
Conditions will turn warmer and brighter over the weekend, with mid-summer heat and humidity expected later next week!