July 13, 2012: Hot, Humid Start To Next Week

Forecast Highlights:

- Mostly cloudy weekend with scattered storms expected
- Short yet intense surge of heat next week; mid-upper 90s NYC and N/W
- Humidity to result in heat index possibly above 100 degrees
- Possible strong/severe storms Wednesday, cooler ending to week


------------------------------------------------------

Thursday, July 12 Observations:

As a slightly warmer air mass moved in with the trough moving out, temperatures ended up slightly warmer than the previous day, reaching the upper 80s to lower 90s from NYC and further north/west. Southern CT had highs in the mid to upper 80s except for SE areas which were cooler, with Long Island in the lower to mid 80s. Partly cloudy skies were observed across the area. Newark, Central Park and LaGuardia peaked at 89 degrees, just 1 degree short of 90 degrees.



Friday, July 13 Observations:

The slightly warmer air mass continued to move into the Northeast, where widespread upper 80s and low 90s were observed. In the area, however, there was more cloud cover than expected, which resulted in slightly cooler temperatures than expected. Temperatures reached the mid to upper 80s from NYC and further north/west, with mid 80s in most of Long Island/S CT except for eastern coastal areas, which peaked in the lower to mid 80s. Newark, Central Park and LaGuardia peaked at 89 degrees for a second consecutive day.



Weekend Outlook:


Cloud cover moved into the region ahead of the original expectation, and as a result mostly cloudy skies and scattered showers and thunderstorms will continue through the weekend. The best risk for storms is on Sunday, when scattered thunderstorms are expected, some of them heavy, although this weekend will not be a widespread regional washout. Temperatures for Saturday are expected to reach the upper 80s to lower 90s from NYC and further north/west and the mid 80s to 90 degrees in most of Long Island/S CT, with temperatures on Sunday slightly cooler, in the mid to upper 80s for most, perhaps cooler further inland and/or closer to the coast, due to the storms and cloud cover.


Next Week: Hot/Humid Start, Stormy Middle, Cooler End

The heat surge mentioned with the previous update is still on track to affect the region and the NYC area, although it is expected to do so a day earlier than first thought, setting up for a 3 day stretch of hot/humid conditions from Monday to Wednesday. Temperatures will begin to warm up on Monday with partly sunny skies, west/WNW winds, and highs reaching the lower to mid 90s from NYC and further north/west and the upper 80s to lower 90s in Long Island/S CT, perhaps a bit cooler further east depending on the sea breeze. Somewhat humid conditions will result in heat index values likely reaching the upper 90s in the immediate NYC area.

The warm air mass is expected to end up over the north central US on Monday, moving into the region on Tuesday and Tuesday night. As a result, the hottest temperatures will likely be on Tuesday, with mostly sunny skies, WNW winds and 850mb temperatures near 20C. High temperatures are expected to reach the mid to upper 90s from NYC and further north/west, and the lower to mid 90s in most of Long Island/S CT, staying below 90 degrees in eastern areas closer to the coast. Humid conditions are expected again, with heat index values likely reaching and/or exceeding 100 degrees in the immediate NYC area.

By Wednesday, a cold front will move through the region, ending the heat. The exact timing of the front is still uncertain, with the slower NAM/DGEX combo and the CMC supporting widespread 90s and possibly low 100s, while the GFS and ECM models are faster, with highs barely reaching 90 degrees followed by widespread storms in the afternoon. 2 days ago the models were still too slow with the front and only recently adjusted towards faster timing, and at this time I am siding closer to the faster ECM/GFS but a little slower, with highs reaching the lower to mid 90s for most of the area with cooler temperatures further east, followed by scattered thunderstorms in the afternoon along with the potential for strong/severe thunderstorms. Stay tuned for more information on Wednesday's outlook.

Behind the cold front, a brief yet strong cool air mass will move in for Thursday and next Friday, bringing another break from the heat. Some models are probably overestimating the temperatures, which are still expected to stay in the 80s in this time frame, likely somewhere around the mid 80s, although temperatures will be back in the near-slightly below average range, with overnight lows in the 50s possible inland. After late next week there is more uncertainty although a gradual warm up is possible.