Thursday will be the last day of the persistent heatwave for the coastal plains and inland valleys of the Northeast. This heatwave has baked cities along the I-95 Corridor from Raleigh to New York since last Friday. However, a cold front emerging from Canada Thursday evening will finally bring an end to the 90+ degree heat, reaching as fast south as the Florida Panhandle, when it arrives between Friday and Saturday.
The heatwave will end with a bang as it sparks thunderstorms along the entire East Coast. Behind the storms, dry Canadian air will replace the steamy temperatures and grace the Northeast with a beautiful weekend. Thursday afternoon through early Friday morning the storms will bring relief to the Ohio River Valley, western Pennsylvania and western New York, as steamy tropical Atlantic moisture collides with cool Canadian air. A few of these storms could develop severe characteristics. Friday morning through Friday afternoon, the storms will inundate the I-95 Corridor and New England. Given the exceptionally high moisture content ahead of the front and the slow upper-level winds, flash flooding in poor drainage areas and along the beds of creeks and small rivers will be a concern where storms continuously redevelop.
The front will clear the coast by early evening, allowing comfortable, dry air to usher in underneath a broad surface high pressure system. The oppressive humidity will immediately be vanquished upon the arrival of this air mass. Dew points will crash from the 70s to the 50s by the time clouds begin to give way to sunshine Friday.
The most noticeable change will be the drastic drop in temperature across a wide area in the Midwest and the East. High temperatures will only be in the mid 70s to about 80 as far west as Des Moines, IA and as far south as Raleigh, NC Saturday. Full wall-to-wall sunshine north and west of Washington, D.C. will make for one of the most pleasant weekends for outdoor activities of the year. The front will stall from coastal Virginia southwestwards, bringing clouds and thunderstorm chances to its vicinity.
Saturday will be the coolest day. Sunday’s highs will be in the upper 70s to about 80 along and west of the Appalachian mountains, but in the mid 80s to the east. Full sunshine is still expected. A developing tropical disturbance in the Atlantic will keep temperatures cooler than normal in the South through Monday. Rough seas associated with the depression will unfortunately result in a rip tide risk Sunday, which would otherwise be a perfect beach day in the Mid-Atlantic and New England.
The cool temperatures are not expected to last long. Above-average temperatures are expected to return by Monday. Another heat wave is possible for cities along the I-95 corridor that could last from Monday to at least Wednesday. The duration of the heatwave is dependent upon the ultimate track and intensity of the tropical disturbance in the western Atlantic Ocean. A stronger, organized system would limit the duration, extent, and intensity of the heat and conversely for a weaker system. Regardless, the heat should stay below record-setting levels, especially north and west of I-95 where 90 degrees could be out of reach.