Catastrophic rain overnight parts of the Northeast, more to come today with severe thunderstorms

Photo bystorm prediction center

Yesterday and overnight rainfall amounts have been nothing short of historic over parts of Southern New England, Long Island, and New Jersey, Areas in Western and Central Connecticut as well as Long Island saw rainfall rates of 2 to 4 inches of rain an hour. Think about it in terms of a months worth of rain compressed in a couple of hours. Rainfall totals have reached over a foot in these hard hit areas. Flash flooding was also common in and around New York City, the lower Hudson Valley, Northern New Jersey and Northeastern Pennsylvania. Roads were washed away, bridges swept by raging waters, search and rescues were the rule overnight. Now comes today and we have one more round of potential thunderstorms and severe weather. The Storm Prediction Center has a risk for isolated severe thunderstorms from Southern Vermont and New Hampshire southward to Eastern Pennsylvania, Southeastern NY, New Jersey, Delaware, Maryland, Eastern Virginia and North Carolina.

Photo byweather prediction center

Given what happened Sunday, we have saturated ground so the risk for additional flash flooding today carries a low threshold. The Weather Prediction Center has a slight risk indicated (15 to 40%) for flash flooding for many areas that got hit hard yesterday and that includes Connecticut and Long Island. The situation today though is different because weather systems are starting to move again from west to east and the log jam caused by Hurricane Ernesto will finally break down. Today is going to be a warm and humid day. The upper trough and cold front will set off thunderstorms and downpours this afternoon and evening but they should not hang around for too long as they move from west to east. Clouds will help to hold temperatures down as highs will reach the upper 70s to lower 80s.

Once thunderstorms are done and offshore we will see a strengthening northwest flow and dew points will collapse overnight and Tuesday. A very large dome of high pressure will build in bringing sunshine and some passing clouds, a nice northwest breeze and high temperatures mostly in the low to middle 70s. Dew points will be dropping into the low 50s and even the 40s giving a nice mid September feel to the air.

Photo byNational Weather Service

Wednesday we have a strong upper low that will be dropping southward from Eastern Canada and into the Northeast. This is likely to create a cold unstable atmosphere aloft and instability. Look for early sunshine giving way to developing clouds Wednesday especially inland. We will include the possibility of some scattered afternoon showers. Temperatures are going to struggle a bit and most highs will be in the upper 60s to lower 70s. In fact many inland areas will have a tough time getting out of the 60s. Wednesday morning and Thursday morning could see widespread lows in the 50s including urban areas like New York City and Philadelphia making this the coolest day since June! Thursday and Friday look like two nice days with no worse than partly sunny skies with highs in the 70s. Dry conditions with relatively low humidity should continue into the start of the weekend.