Aug 13, 2013 Storm Updates

Below, storm updates will be posted on the heavy rain and thunderstorms affecting the area throughout the day. Updates are being posted both on the blog and on Twitter. The next forecast discussion will be posted this evening. Radar images are from the National Weather Service.

Yesterday’s Forecast Discussion
5-Day Forecast


9:05 PM: Scattered Storms Moving Through

0048The morning round of thunderstorms cleared the area early this afternoon, with at least 1/2 to 1 inch of rain falling across most of the area, locally up to 1-2 inches towards western NJ, but with less rain than expected over southern CT, under 1/4 inch. Mostly cloudy skies continued through the mid-late afternoon with partial clearing in the cloud cover and temperatures rising into the mid to upper 70s across the area.

The cold front is currently located over western NJ, with a broken line of thunderstorms just ahead of the front over western NJ and western CT. Ahead of these storms, an isolated storm developed near Cresskill, NJ (Bergen), and will move into southern Westchester county by 9:30 PM with moderate rainfall. A strong storm is located near West Milford, NJ (Passaic), and will move ESE into northern Passaic and west-central Bergen counties by 9:45 PM, while another line of strong storms over Warren county will gradually move through Morris county, both storms producing locally heavy rainfall up to/over 1/4 inch. Instability will continue to decrease with the loss of daytime heating, with these storms likely to weaken as they reach and pass NYC within the next 1-2 hours.

This is the last storm update for today. A forecast discussion will be posted later tonight with a review of today’s event and more information on the upcoming cooler than average temperatures.


12:00 PM: Rain Starting To Move Out

1538After the last update, rain began to move out of the immediate NYC area, northern NJ and SE NY; rain totals in the immediate NYC area and northern NJ are generally between 1/2 and 1 inch. Heavy thunderstorms continue to persist off the New Jersey coast, with moderate to locally heavy rain continuing over Long Island, especially near the south coast where radar estimates show up to 1/2 inch. Southern CT, however, has seen generally light to occasionally moderate rain so far with totals mostly less than 1/4 inch, locally higher further west.

The latest satellite shows clearing in the cloud cover in western NJ, which will continue to spread east through the rest of the area over the next few hours as temperatures gradually rise into the mid to upper 70s. Additional scattered thunderstorms are expected to develop in Pennsylvania later this afternoon, moving through western NJ towards the evening after 5 PM, likely weakening as they move into and east of NYC with loss of daytime heating.


10:00 AM: Rain Weakens

1338Following the last update, the thunderstorms in southern NJ intensified while splitting from the main batch of rain, with the moderate-heavy rain starting to expand east into NYC and Long Island/CT but with the rain weakening overall. The rain is likely to continue to slowly weaken as it continues to shift east into NYC and Long Island/CT over the next 1-2 hours, with lower rain totals than previously expected, at least near 1/2 inch in the immediate NYC area, locally higher up to 3/4-1 inch, and lower to the east of NYC. The ending time is earlier than expected as well, ending by 11 AM in western NJ and 12-2 PM further east. The rest of the outlook remains unchanged with some clearing in the cloud cover, highs reaching the mid-upper 70s, and scattered late afternoon-evening storms primarily west of NYC.


8:40 AM: Rain Continues To Approach

1218Over the last hour, rain spread into most of the area, focusing primarily over western NJ where at least 1/4 to 1/2 inch of rain fell so far. The rain, however, is struggling to expand east, drying up east of Morris county with only light to moderate rain reaching NYC. The severe thunderstorms over southeast PA from earlier this morning have weakened, with one low-end severe storm remaining in southern NJ. Heavy rain will continue over western NJ through the late morning-early afternoon with at least 3/4 to 1.5 inch of rain expected, with 1/2 to 3/4 inch in the immediate NYC area and further east, locally higher. The rain is expected to move out by 12-3 PM with clearing skies afterwards and a few scattered evening thunderstorms.

7:00 AM: Heavy Rain Approaching NYC

1048Yesterday’s update noted a pre-frontal trough will approach the region, with rain and thunderstorms, locally heavy, affecting PA, NJ, NY and New England in the late overnight and morning hours with over 1/2 to 1 inch of rain possible. The latest radar, posted to the left, shows a large area of heavy rain and thunderstorms over Pennsylvania and a smaller area over central NY, both of which are moving ENE. The former area of rain contains strong-severe thunderstorms over SE PA, capable of producing strong wind gusts and hail; these storms will remain south of the area, with heavy rain and thunder otherwise continuing NE into the area.

Starting times are likely to be around 7:15 to 7:30 AM in NYC and its immediate suburbs, 7:30 to 8 AM in the western half of Long Island-CT, and 8-9 AM in the eastern half. This heavy rain is expected to continue through at least 1-4 PM, ending from west to east, with 1/2 to 1 inch of rain across most of the area, locally higher especially from NYC and west/south. Once this moves out, clearing in the cloud cover will take place for the late afternoon and evening with temperatures rising to peak in the mid to upper 70s, while additional scattered storms develop in Pennsylvania and approach New Jersey, associated with the actual cold front. These storms may be locally strong with strong wind gusts and small hail with the stronger cells, although widespread strong-severe storm activity is not anticipated, and these storms are likely to stay primarily west of NYC, weakening as they advance further east as they approach a more stable air mass along with the loss of daytime heating.

Additional storm updates will be posted throughout the day. The next forecast discussion regarding the upcoming chilly temperatures and the outlook for next weekend will be posted tonight.


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