An offshore high pressure system has been slowly sliding south from the Canadian Maritimes since this weekend. While it's been keeping us dry, it's also created an onshore flow off the Atlantic Ocean. This has led to low clouds and fog developing overnight and sunshine breaking out as the day progresses, a pattern that will continue again Wednesday. Wednesday night into Thursday, there's something new to watch... An area of low pressure with tropical characteristics that will lift north from the Southeastern United States into the Mid Atlantic. This will present the possibility for a shower over this stretch with perhaps a thunderstorm in spots Thursday. That low will dissolve into an approaching low and cold front by Friday as the offshore low positions itself by Bermuda. The combination will send temperatures soaring, humidity levels to rise, and increase the threat for showers and a thunderstorm. While the cold front's passage may lingering into Saturday morning, along with a shower or thunderstorm, the trend during the first half of the weekend will be toward drying out as high pressure builds in from the Midwest.
As has been the case the past couple nights, the offshore high that leads to lots of afternoon sunshine also causes the clouds to build and fog to develop at night and that will happen again tonight. With higher dew points, we can also expect warmer overnight lows as temperatures stay in the 60s, albeit lower 60s. This means the comfortable nights we've experienced for most of May are a thing of the past for the rest of the work week.
With the offshore low now even farther south the sunshine should break out even faster than the previous two days. However, while the low clouds will be breaking faster the encroaching low to our west will start streaming high clouds into the area by midday. This means that most of the sunshine that we do see on Wednesday may be of the milky variety. While still above normal, daytime highs will take a slight hit on Wednesday as they fall back closer to 80°. Dew points will continue to be the near 60° to middle 60s range, so it'll once again be noticeable.
Thursday will be a bit "cooler" than Wednesday with highs near 75°, though we should start to notice the humidity even more as the high slides closer to Bermuda and slowly starts to breakdown. This will allow more moisture to creep into the Eastern Seaboard. At the same time, a cold front to our west will continue to inch closer, resulting in even more instability. So, there's a chance for showers and thunderstorms, really at any point in time during the day. There will still be some dry times, though they're met by plenty of clouds.
Friday will feature our greatest chance for showers and thunderstorms as the aforementioned cold front to our west tracks through. However, it may take a little while to get them. Warm and humid air will be in place out ahead of the front, so expect a classic summer-like day with highs in the mid 80s, some sunshine, and scattered showers and a thunderstorm by the afternoon and evening. In fact, a few storms could be locally strong or even severe.
The cold front is expected to exit the East Coast early on Saturday, so while there may be a leftover shower or thunderstorm early the trend of the day will be drying out. We'll also see dew points fall off as sunshine returns and temperatures top out in the low 80s.