Compared to the previous month, severe weather was a bit less widespread in June 2019. However, the same active pattern that we saw in May continued through the first half of the month, with intervals of upper level ridging and troughing. This pattern brought warm-ups followed by cool shots through the first two weeks, especially across New England. By the second half of the month, however, this all started to change. More prominent and longer lasting ridging pushed in increasingly humid and tropical air masses. This allowed temperatures to finally surge well into the 80s and 90s for longer stretches of time across a good chunk of the I-95 corridor. This not only led to a renewed risk in severe weather, but also flooding along the Mason-Dixon line, around Philadelphia, and in southern New Jersey.
The first weekend of June continued with some severe weather, as a series of frontal passages brought showers and thunderstorms. Hail and damaging winds accompanied these storms from Virginia all the way up through the lower Hudson Valley. While temperatures sat in the 70s and 80s across most of the I-95 corridor, a stalled out boundary kept temperatures in the 60s and lower 70s through the first half of the week over much of Massachusetts and northern New England.
Although the severe weather subsided some the following week, it still remained active with daily shower and storm threats in the Northeast. Temperatures as a whole were near average from D.C. to NYC, though slightly below average from Hartford to Boston. Precipitation was also near normal, with most places roughly picking up anywhere from 0.50"-1.00" of rainfall.
By the middle of the 2nd week of June, an active pattern locked in as more disturbances and frontal boundaries became increasing impactful. June 13th started what would be a string of busy weather days, with severe storms dropping heavy rain (1"+ in some areas) and damaging winds across the Mason-Dixon line, southern NJ and around Philadelphia. Two tornadoes also occurred with this severe set-up, with an EF-0 in Gloucester, NJ and an EF-1 in Cecil County, MD.
A ridge of high pressure off the eastern seaboard helped keep this pattern in place during the 3rd week of the month. More disturbances brought daily threats of showers and thunderstorms. Although there were some strong-severe storms between the 16th and the 20th (mainly over the DelMarVa), it was the flooding that became problematic by the end of the week. Slow moving storms brought heavy rainfall from southeast PA into southern NJ, with Philadelphia recording over 4" of rainfall in a short span of time.
A bit of a reprieve from showers and storms arrived by the last week of the month, though this ridge of high pressure helped to bring in more tropical air masses. This led to not only an increase in humidity, but also an increase in temperature. Areas from D.C. to Philly saw back to back days in the 90s, with even areas near Boston finally seeing back to back days in the 80s. Though most of the week ended up quiet, one disturbance on the 29th led to widespread strong to severe storms from the Nation's Capital through New England.
The storm events during the middle to later half of the month led to near to above average rainfall for many. Philadelphia was the biggest outlier of all the major I-95 cities, as they picked up almost double their monthly rainfall. Temperatures also ended up near to slightly above normal for most of the Northeast, thanks to the end of the month warm-up.