A cold front is slowly moving towards the region today, with scattered thunderstorms, locally heavy, expected tonight and tomorrow as warm and humid conditions continue. The front will move through on Tuesday, with cooler, drier and less humid conditions for the rest of the week. A fluctuating temperature pattern is then likely to follow as the region alternates from trough to ridge with temperatures ranging from below to above average.
Today – Tuesday: Storms Continue; Warmth, Humidity Gradually End
As of 10 AM, a closed upper level low was located north of Michigan, with the surface low pressure located approximately near the same location with the cold front extending southwestward towards Ohio and Kentucky. While the front is still well to the west, a pre-frontal trough moving through as well as several shortwaves will produce scattered showers and thunderstorms across the region. A moist and humid air mass remains with dew points in the low 70s and precipitable water values near 2 inches, capable of supporting heavy rainfall and possible localized flash flooding with the stronger storms, likely to be focused to the north and NE of NYC. The front will then slowly move through the region tonight into Tuesday with additional scattered storms up to the frontal passage.
For the short term, most of the area is currently dry aside from scattered storms in northern Fairfield county in CT and Warren county in NJ. Widespread storms failed to materialize last night, with continued scattered storm activity focused mainly to the north of the area. There is some uncertainty regarding the exact timing of the storms today with the multiple shortwaves moving through, although the overall idea at this time is for another round of storms in the early-mid afternoon hours, with possible starting time ranging from approximately 12 PM to 3 PM, which may last for a few hours before winding down. Highs are expected to reach the low to mid 80s across the area. Less storm activity is likely overnight, with additional scattered storms possible on Tuesday morning prior to the frontal passage, especially near NYC and further south/east. Highs are expected to reach the low to mid 80s again, with a south wind becoming NW and gradually decreasing humidity.
As previously mentioned, there is still some uncertainty regarding the exact timing of storms. Storm updates will occasionally be posted this afternoon both on the blog and on Twitter, including any updates on changes in the forecast.
Wednesday – Beyond: Drier, Fluctuating Temperature Pattern
A cooler and drier air mass will return into the region behind the cold front, with high temperatures on Wednesday and Thursday ranging from the mid-upper 70s inland to the low 80s near NYC, and overnight lows in the mid 50s-low 60s away from NYC and the coast. A strong upper level low will dive southeast through Canada, entering the region on Thursday night into Friday, with a strong yet brief colder air mass moving in with 850mb temperatures dropping below 10C. As a result, clearing skies and chilly temperatures are expected for Thursday night, with lows likely to fall into the mid-upper 40s inland, low-mid 50s in the north/west suburbs of NYC, interior Long Island, and southern CT, and the upper 50s near NYC and the immediate coast; the temperature outlook on Thursday night is subject to minor changes. Mostly sunny skies are then expected for Friday with highs ranging from the upper 60s-low 70s inland to the mid to possibly upper 70s across the rest of the area.
The cooler temperatures on Friday will begin a fluctuating temperature trend, with more frequent ups and downs. The trough will quickly lift out on Friday as the surface high pressure spreads east, bringing a SW wind into the area. This will result in a quick warm up for the weekend, with highs returning into the upper 70s-low 80s on Saturday and the low-mid 80s on Sunday. Meanwhile, another upper level low will brush the region, with a cold front likely to move through around Sunday, possibly producing scattered showers and thunderstorms, followed by another cool down for Monday and possibly Tuesday; temperatures are still uncertain, but may be somewhat similar to those of the Thursday-Friday cool spell, and likely followed by another warm up later into the week. Meanwhile, the tropics will be monitored for the longer range as well, as either invest 97L, currently just east of the Lesser Antilles, or another tropical wave behind it, may develop into a tropical cyclone while tracking near or north of the Greater Antilles (Puerto Rico, Hispaniola, Jamaica, Cuba).