July 21, 2013: Rain Returns This Week

Forecast Highlights:

A cold front that slowly approached the region in the last few days is moving through today, bringing an end to the 7-day heat wave for most of the region, although some locations are still expected to reach the low 90s today. The frontal boundary will stall nearby most of the week with occasional rounds of scattered storms and thunderstorms, especially in the middle of this week and possibly next weekend, with high temperatures cooling back down into the 80s.

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Today: Slightly Cooler, 90 Degrees Still Possible

A pre-frontal trough affected the region yesterday with scattered storms, some of them strong to locally severe, although no widespread storm activity was observed yesterday. The cold front is still slow to move through the region, and was still north of the area as of ear;y this morning. The front is weakening, however, and will fail to produce more than isolated storms south of the area. Since the front is weak and slow moving, it will fail to completely remove the warm air mass, with highs today peaking in the mid to upper 80s inland and the upper 80s to low 90s across the rest of the area, although humidity will be noticeably lower with dew points in the low-mid 60s. The frontal boundary will fail to push far to the south of the area, with overnight lows staying in the mid 60s to low 70s.


Next Week: Some Storms, Slowly Cooling Down

While originally, the model guidance indicated the frontal boundary would slide south of the area and remain stalled nearby, the front is slower than modeled a few days ago, and will gradually slide south into the area and offshore in the first half of the week. Strong ridging will set up over the central Atlantic ocean with 500mb heights up to 600dm, keeping a longwave trough in place over the eastern US with several weak shortwaves moving through the region, bringing a constant chance of scattered showers and thunderstorms into the region throughout the week.

Given the expected set up, it is difficult to narrow down exactly when it will rain and how much, although isolated storms are currently expected for Monday, with a higher risk of scattered storms on Tuesday, Wednesday and Thursday, some of which could produce locally heavy rain. High temperatures are expected to generally peak in the low to mid 80s inland and the mid to upper 80s across the rest of the area, which is overall close to average, with overnight lows remaining warmer than average, in the mid 60s to low 70s.

Beyond the late week outlook, the model guidance shows another possible storm for next weekend with more widespread rain, while the trough remains in place through the end of the month, keeping temperatures generally near average. Some longer range signals especially from the GEFS suggest the next potential surge of heat may be in early August. More information on this week's outlook will be posted throughout the next few days.

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Friday, July 19 Observations:

The peak of the heat wave took place on Friday, with partly sunny skies and a few isolated storms near Long Island but generally dry elsewhere. Highs reached the low to mid 90s in Long Island and southern CT and the mid to upper 90s for NYC, northern NJ and SE NY. The hottest temperatures were observed in the immediate NYC area, with Newark, LaGuardia, and Teterboro reaching 100 degrees. Along with dew points in the upper 60s to mid 70s, heat indices reached the mid to upper 100s, in some cases the low 110s.

Minimum daily temperatures were mild, failing to fall below 80 degrees in NYC and parts of NE NJ. LaGuardia recorded a low of 86 degrees, tying August 2, 2006 and July 5, 2005 for the highest minimum temperature on record. Bridgeport, CT, with a low of 80, also tied the highest minimum temperature of record with July 4, 2002.

Record highs on Friday, July 19, 2013:

LaGuardia, NY
100 degrees (previous record: 99 degrees - 1977)
Islip, NY
93 degrees (previous record: 92 degrees - 1999)
Newark, NJ
100 degrees (tied record: 100 degrees - 1999, 1977)

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Saturday, July 20 Observations:

A weakening cold front moved through the region, producing scattered thunderstorms; a severe storm moved through portions of southern CT, with scattered strong storms in NYC, Union county, and western-central Long Island in the late afternoon and evening. Temperatures were slightly cooler than those on Friday, but with hot and humid conditions returning for the 7th consecutive day, with highs peaking in the low to mid 90s across the area. The highest temperature was 96 degrees in Newark and JFK.

Record highs on Saturday, July 20, 2013:

JFK Airport, NY
96 degrees (tied record: 99 degrees - 1991)