July 22, 2013: Occasional Storms Today, Tomorrow

Forecast Highlights:

A weak frontal boundary slowly shifted through the region yesterday, with temperatures falling back down to near average as the hot and humid air mass from last week was pushed offshore. This frontal boundary will remain near the region through the rest of the week and weekend, with occasional rounds of showers and storms, such as today and Tuesday and possibly next weekend, continuing into at least early August.

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Sunday, July 21 Observations:

Following the scattered storm activity on Saturday, the weak cold front moved through the region, with lower humidity and slightly cooler temperatures observed across the region. High temperatures reached the low to mid 80s in Long Island and southern CT and the mid to upper 80s for the rest of the area. Temperatures failed to reach 90 degrees across most of the area, breaking the 7-day heat wave that started on Sunday, July 14, except for Teterboro and Somerville in NJ that reached 90 degrees, extending the heat wave to 8 days.

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This Week: Occasional Showers, Storms; Seasonable Temps

The latest radar image, posted to the left, shows scattered showers and storms developing across the region, especially in Pennsylvania and New Jersey. These storms are generally slow moving and are producing locally heavy rain and flash flooding. Around 1-2 PM, a line of heavy storms moved north from NYC into NE NJ, producing 1/2 to 1 inch of rain based on radar estimates; as of 2:30 PM the line is currently located over SE NY and continues to slowly move north, producing heavy rainfall.

A wave of low pressure is expected to develop over the region tonight, continuing the scattered storm activity through this evening producing locally heavy rain and flash flooding, with the low developing tonight into Tuesday morning as the heavy thunderstorms shift north to focus over NY state. Throughout the afternoon and evening, the cold front will slowly approach the area with increasing coverage of showers and thunderstorms especially west of NYC, where storms will be capable of producing locally heavy rain. Temperatures will be cooler as well, peaking only in the low to mid 80s for highs.

The cold front will shift offshore for Wednesday through Friday, with temperatures falling down to slightly below average levels, with partly cloudy skies and highs reaching the mid 70s to low 80s across most of the area. The ECM is currently aggressive in showing a wave of low pressure producing widespread rain on Friday, although is an outlier compared with the rest of the model guidance, and at this time I am siding with any wave of low pressure staying offshore with dry weather continuing into Friday.


Weekend - Next Week: Some Rain; No Sign Of Heat Yet

A trough is expected to remain in place over the Northeast through the medium range, blocked from progressing offshore by a massive ridge in the central Atlantic Ocean. An upper level low is expected to track into the Great Lakes region, with a surface low pressure developing west of the area and tracking north, with a cold front likely to move through around Sunday based on the latest model guidance. Another round of showers and thunderstorms is expected, with the heaviest rain based on the latest indications likely to stay north and west of the area; a cooler than average air mass is then likely to reach the region early next week with 850mb temperatures nearing 10C, supporting high temperatures generally in the mid 70s to low 80s. Going into early August, the long range model guidance is backing down on earlier indications of heat returning as the mean trough stays over the region, although a gradual warm up is likely into next week. Stay tuned for more information on the longer range.