July 7, 2012: Forecast Review; Heat Finally Ends

Forecast Highlights:


- Long lasting heat wave to end tomorrow
- Seasonable, mostly dry conditions for early-mid week
- Warmth, humidity, some storms to gradually return for longer range


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Tonight's update was focused on today's review. The rest of the pages will be updated on Sunday.

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Today's Overview: What Went Wrong


Today was a difficult day to forecast; the general part of the forecast verified with hot temperatures and scattered storms, but the specifics of the forecast ended up busting. There was already some uncertainty with today's forecast going back a few days ago when there were two main solutions; either a slow cold front that would result in thunderstorms staying in New England while NYC bakes in 100 degree heat, or a faster cold front that would bring storms closer to the area while temperatures still reach the upper 90s to lower 100s. Two days ago there was more confidence in the slower cold front scenario, but short range changes with the scenario ended up favoring the faster cold front scenario, which yesterday's models trended towards.

With a faster cold front timing expected, the outlook as of last night already had a little doubt on exactly how hot temperatures would get depending on afternoon cloud cover and evening storms, but there were even more changes to the forecast for the short range. Today's forecast became more complicated with a complex of storms that moved into southern New York state this morning; the models did not handle the storms correctly, either showing them too weak or too slow. As a result, both the temperatures and storms did not end up verifying as expected.

Temperatures: With clouds already moving into most of the area by 12-1 PM, the temperature rise was stopped earlier than expected, which prevented widespread 100+ degree heat. Despite the earlier than expected clouds, there was still enough sunshine for at least the immediate NYC area and Long Island to get close to the expected temperatures, with mid to upper 90s in the immediate NYC area and mid 90s for most of Long Island. Newark reached a peak of 102 degrees, with 99 degrees in JFK and 97 degrees in Central Park, making it the hottest day of the year for most of the immediate NYC area.

Further north, however, the temperature rise was prevented due to the cloudy skies and widespread showers associated with the morning storms, that weakened as they moved east, producing light rain over SE NY and southern CT. These areas saw highs in the upper 80s to lower 90s, which was cooler than expected. These temperatures were reached despite the early cloud cover, if the cloud cover didn't move in earlier than expected, there is a good chance temperatures would've been higher than what was observed today.

Storms: The storm outlook was also complicated as a result of the morning storms that dissipated over southern CT. Once the weakening storms came through, temperatures dropped earlier than expected, and there was not as much instability as originally expected. This was especially true over SE NY and southern CT, which after the morning storms only saw isolated evening storms. Afternoon severe storms developed over western NY and were originally expected to continue moving ESE getting close to at least western NJ, focusing west of NYC, but ended up diving more SE, instead producing an axis of severe thunderstorms in central NJ where damaging winds and power outages were observed. With the afternoon storms staying SE, no new development took place over most of the area for the rest of the afternoon and evening hours except for the isolated CT activity mentioned earlier, which moved into eastern Long Island.

There were some models showing isolated activity reaching the area later in the overnight hours, and scattered storms did end up forming over northeastern Pennsylvania late this evening. These storms became more widespread and stronger than expected, however, as they began to move into the area around 11:30 PM. The evening storms ended up being almost entirely focused on an axis between Morris county to Manhattan and Nassau county in Long Island, where heavy rain and windy conditions are still ongoing. This time there is little uncertainty in the forecast for the rest of the night for the storms to gradually diminish over the next few hours, with isolated storms still moving through the axis mentioned above but not as frequent as the storms observed over the last hour. There is also another area of storms near NW PA that may bring additional scattered storms west and SW of NYC late tonight into the morning hours, although as the cold front continues to slowly move south, the next round of storms, should it survive through the overnight hours, is more likely to be focused further south.


This Week: Heat Ends For Now


Throughout the day, a strong low pressure developed over SE Canada, with a cool air mass associated with the trough over SE Canada dropping south into the region behind the cold front currently moving through. As the cold front moves south, it will slow down, eventually stalling over the southern Mid Atlantic for early-mid next week. As a result, dry conditions, partly sunny skies and seasonable temperatures are expected. Warm temperatures are still expected for Sunday with upper 80s to lower 90s for most of the area, cooling down for Monday into the mid week with highs generally in the mid to upper 80s, except for coastal areas which will likely be slightly cooler. Overall, temperatures will remain near average for the first half of next week as there is no widespread rain or a strong cool air mass associated with this trough.

Going into late next week and the weekend, there is more uncertainty with the exact scenario, although the trough is expected to weaken as a slightly warmer air mass moves into the region. While no large heat wave is expected at this time, temperatures are likely to gradually warm up with a potential for some storms towards the late week and the weekend. Stay tuned for more information on the longer range outlook.