Aug 31, 2013: Warmth, Humidity, Storms Until Monday

Forecast Highlights:

northeast6A warm and humid air mass will remain in place on Sunday and Monday, with highs in the mid 80s away from the coast along with scattered thunderstorms, especially on Sunday night through Monday night. A cold front will move through the area on Tuesday, bringing a drier air mass with more seasonable temperatures for the rest of the week into next weekend, but with a 1-day surge of stronger cool air possible for Friday.


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Friday, August 30 Observations:

8.30.13A back door cold front left the region, with cloud cover early in the day clearing with more sunshine towards the afternoon and evening. With a west-SW wind resuming, warmer temperatures were observed compared to Thursday, peaking in the low to mid 80s away from the coast, where temperatures reached the upper 70s. The highest temperature was 86 degrees in Newark, NJ and LaGuardia, NY, and the coolest high temperature was 77 degrees in multiple locations.




Tonight – Monday Night: Warm, Humid, Stormy

With a WSW flow setting up in the low-mid levels, a warmer and more humid air mass is present over the region with dew points generally in the upper 60s to low 70s and 850mb temperatures near 16-18C, which are expected to remain in place for Sunday and Monday. Widespread cloud cover is also present, however, with scattered thunderstorms across the region; the latest radar image in the top of this post shows scattered storm activity north of the area, where most of today’s storms were focused, although a few isolated storms were observed north and west of NYC as well. Conditions for Sunday are expected to be similar to those of today with highs in the low-mid 80s away from the coast, which combined with the humidity will result in heat index values in the upper 80s-low 90s, bringing a summer-like start to the meteorological fall.

A stronger trough will dig into the region on Monday as a pre-frontal trough at the surface moves through the region, with widespread showers and thunderstorms expected. While the exact timing is subject to change, at this time two rounds of storms are likely, one on Sunday night into Monday morning associated with a strong shortwave moving through the region, with heavy thunderstorms possible especially north and west of NYC, and a second round of thunderstorms in the evening and overnight hours mostly west of NYC ahead of another shortwave as the surface cold front slowly approaches. While widespread severe weather activity is not anticipated given the widespread cloud cover and marginal shear/lapse rates, storms could be locally strong with heavy rainfall and strong winds possible. The latest models indicate a period of dry conditions and possibly some sunshine during the afternoon hours, which is still an uncertainty but a potential that will be watched. Slightly cooler high temperatures are expected, peaking in the low 80s for most of the area.


Tuesday – Next Weekend: Cooler, Drier

As the upper level low tracks northeast into Canada, the cold front will slow down while moving east through the area, supporting scattered showers and thunderstorms lingering through Tuesday morning and possibly afternoon, gradually ending from west to east. Temperatures are likely to peak in the low 80s across the area with a gradual lowering of humidity, especially towards the evening and overnight hours. Mostly sunny skies are expected to return for Wednesday with highs in the upper 70s to low 80s.

The pattern over the longer range is likely to consist of persistent ridging centered over the western US, with lower heights aloft over the northeast US region as a troughing pattern likely continues over eastern Canada. A strong upper level low will dive southeast through Canada, reaching the region on Thursday into Friday while bringing a quick round of much cooler temperatures. There is some uncertainty regarding the southern extent of this colder air mass, although the coolest temperatures are expected to remain north of the area. The most significant effects from this air mass will be felt on Thursday night, with overnight lows likely to fall into the 40s range inland and the 50s for most of, if not the rest of the area, with daytime highs likely at this time to peak in the mid 70s to near 80 on Friday. Towards next weekend, the trough will quickly lift out with temperatures warming back into the low-mid 80s, but with another trough possibly approaching towards early next week.

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