A strong trough is currently in place over the area, resulting in cooler than average temperatures and mostly sunny skies across the region. A frontal boundary will slowly approach the area on Tuesday and Wednesday, resulting in increased cloud cover and scattered showers, with a wave of low pressure producing rain and thunder, possibly heavy, from Thursday through early Saturday, followed by another round of slightly cooler than average temperatures.
Today – Wednesday: Cooler Than Average
The current upper level pattern, shown to the left with the initialized 0z GFS 500mb heights across North America (image credit: NCEP MAG), shows a strong upper level low over the Hudson Bay, with troughing extending southeast to reach the Northeast US region. The ULL is trapped beneath relatively strong ridging to the north and west, which will force it to swing to the south, lifting the current trough out of the region and setting up for a more westerly flow aloft overhead, which will advect a warmer and more moist air mass into the region from the west and southwest as a surface warm front slowly makes its way into the region.
As of this morning, temperatures are unseasonably chilly, having reached the 50s away from the coast and getting as low as 50 degrees in Sussex, NJ. With a surface high pressure building into the area, mainly sunny skies are expected today with light northwest winds and highs reaching the mid to upper 70s inland and the upper 70s to low 80s across the rest of the area. Mostly clear skies are expected again tonight with temperatures similar to those of this morning, with partly sunny skies on Tuesday and highs reaching the upper 70s inland and low to possibly mid 80s across the rest of the area. By Wednesday, the aforementioned warm front will continue to slowly approach the area, with mostly cloudy skies and occasional showers expected, especially west of NYC, with minimal amounts under 1/4 inch. With a breezy SSE wind, cloud cover and rain, cooler temperatures are expected, peaking in the low to mid 70s in western areas and mid 70s to near 80 degrees for the rest of the area.
Thursday – Friday: Rain, Possibly Heavy
The warm front is expected to move through the area on Wednesday night, pushing a warm and moist air mass into the region with precipitable water values near 2 inches, suggesting storms will be capable of producing heavy rainfall along with a potential for localized flash flooding. Widespread showers and thunderstorms are expected overnight into Thursday morning, with the potential for near/over 1 inch of rain especially north of NYC. Drier conditions are expected on Thursday as the area enters the warm sector, with increased humidity, mostly cloudy skies and high temperatures reaching the low to mid 80s away from the coast. Scattered thunderstorms can’t be ruled out, especially in the morning, although drier conditions appear likely at this time for the majority of the day.
As the upper level low in southern Canada begins to track east, then northeast, the surface cold front will gradually approach the area. Another round of rain and non-severe thunderstorms is likely on Friday and/or Friday night as the front slowly moves through the region, possibly extending into Saturday as well depending on the exact setup of the trough which is subject to some changes. Should the front progress offshore on Saturday as currently modeled, a brief spike in temperatures is likely with westerly winds and relatively mild 850mb temperatures, with highs peaking in the mid to upper 80s across most of the area.
Sunday into early next week is expected to be cooler again as the trough covers the region again, with highs likely back into the upper 70s-low 80s range with lows in the 50s to low 60s away from the coast. This round of cool temperatures is not forecast to be as strong as the current round, however; the upper level low will be well to the north over central Canada, and the cool air mass is likely at this time to remain relatively short lasting with the next storm potential towards mid-late next week. Stay tuned for more information on the longer range.
Saturday, August 3 Observations:
A weak cold front moved through the region, producing a round of showers during the morning with rain totals under 0.1 to 0.25 inch, followed by additional late afternoon and evening isolated shower activity. Temperatures were cooler than average again, peaking in the mid 70s to near 80 degrees across the area; the warmest temperature was 80 degrees in Newark and LaGuardia, with 76 degrees the coolest high temperature in New London and Bridgeport, CT
Sunday, August 4 Observations:
Behind Saturday’s frontal passage, a strong trough entered the region with a cooler air mass slowly entering, keeping temperatures several degrees cooler than average despite more sunshine than Saturday. High temperatures reached the upper 70s in northwestern areas and the low to mid 80s for the rest of the area; the highest temperature was 83 degrees in JFK and Bridgeport, CT, and the coolest high temperature was 76 degrees in Port Jervis, NY and Sussex, NJ.