July 11, 2013: Another Heat Wave Next Week

Forecast Highlights:


As noted earlier this afternoon, a drier scenario than expected set up for today as the cold front moved through faster than expected and thunderstorms failed to develop north of the Mid Atlantic. Additional isolated or scattered showers are expected on Friday into Sunday as the frontal boundary stalls nearby and slowly dissipates. By next week, however, strong ridging is expected to build into the region, resulting in another heat wave with more heat and humidity than last week, with temperatures possibly approaching the upper 90s.


Tonight – Sunday: Isolated Storms, Cooler/Less Humid

With the cold front moving through the area, a noticeable decrease in humidity is expected as dew points fall into the upper 50s and low 60s. Mostly cloudy skies are expected to continue tonight with a north wind and cooler lows than the last few nights, falling into the low to mid 60s away from NYC and the coast, which will remain in the upper 60s to low 70s overnight. The cold front will stall to the east, with mainly cloudy skies and isolated showers/storms expected again for Friday and Saturday. Based on the latest trends over the last few days, widespread rain coverage is not expected, although storms that do form may be capable of locally heavy rainfall. The cloud cover and areas of rain will keep high temperatures slightly below average, peaking in the mid 70s to low 80s for highs across the area. The frontal boundary is expected to weaken and shift west on Sunday, keeping the remnants of tropical storm Chantal well to the south of the area as well, with more sunshine and warmer temperatures reaching the low to mid 80s near the coast and the mid to upper 80s elsewhere, although an isolated afternoon thunderstorm can’t be ruled out.

Next Week: More Heat, Humidity Than Last Week

The pattern since mid June has generally consisted of several days of heat and humidity, followed by a frontal boundary bringing scattered storms for several days followed by another heat wave as western Atlantic ridging spreads into the region. This case is forecast to be similar, with ridging spreading from the western Atlantic Ocean into the region, where a large ridge with 500mb heights over 594 dm is expected to stall overhead for the early-mid week, which along with 850mb temperatures near 20C and a west/WSW wind is expected to result in yet another heat wave, with even hotter temperatures than last week.

Hot temperatures are expected to become more noticeable on Monday, with the hottest temperatures likely at this time between Tuesday and Thursday. Highs are initially likely to peak in the upper 80s to low 90s away from the coast, warming by the late week into the mid 90s, possibly the upper 90s should the warmer case scenario verify. Each day is generally expected to be mostly to partly sunny, although a few isolated afternoon thunderstorms can’t be ruled out. Humid conditions are expected as well, with dew points likely in the upper 60s to low 70s resulting in heat index values approaching and/or possibly exceeding 100 degrees. The exact temperature outlook is subject to some changes as this is still in the medium range, although the heat and humidity are likely to continue until late next week when the next cold front approaches, bringing the next potential for storms and lower temperatures/humidity. Stay tuned for more information on next week’s outlook.

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