July 28, 2013: Scattered Interior Storms Today

Forecast Highlights:

northeast4A slow moving cold front will slowly cross the region this evening and tonight, producing scattered thunderstorms especially north and west of NYC. Seasonable conditions will return for the first half of this week, with two systems, one on Thursday, and another on Saturday-Sunday, affecting the region with additional showers and thunderstorms; a brief warmth surge may be possible on Saturday, but with sustained heat remaining nowhere in sight.



Saturday, July 27 Observations:

7.27.13 - CopyAs Friday’s coastal low exited the region, a weak high pressure spread into the region, resulting in more sunshine and slightly warmer temperatures. Partly sunny skies were generally observed with high temperatures reaching the upper 70s to lower 80s in Long Island and southern CT, and the low to mid 80s from NYC and further north and west. The highest temperature was 87 degrees in Teterboro, NJ.





Today – Wednesday: Stormy Today, Then Seasonable

A strong upper level low is currently located in the Great Lakes region, with a surface cold front slowly moving east towards the region. This front is expected to trigger scattered storm development this afternoon and evening, primarily in eastern PA and NY, where some storms may be strong, but the thermodynamic environment is generally unfavorable for more widespread severe weather with widespread cloud cover limiting instability, marginal bulk shear and unfavorable mid level lapse rates. The storms that do become strong are likely to focus in the eastern PA to SE NY axis and may be capable of gusty winds and heavy rainfall, with localized flash flooding possible. In the NYC area, isolated afternoon storms are possible north and west of NYC with highs in the low to mid 80s for most, with scattered storms moving in during the evening hours, weakening as they reach NYC. Storms are likely to eventually collapse overnight as the front moves through the area.

The upper level low will continue to track northeast into Canada, lifting the unseasonably cold air mass in the Great Lakes back north as well. As a result, along with a southwesterly flow setting up, temperatures will fail to cool down behind the front, with highs remaining close to average, in the low to mid 80s along with partly sunny skies for the first half of the week. Overnight lows will be cooler though, ranging from the mid-upper 50s inland to the mid-upper 60s near NYC.

Thursday – Next Weekend: More Storms

A longwave trough is expected to settle over southern Canada for the medium range, resulting in a temperature gradient ranging from cooler than average temps in the northern US to above average temps in the southern US. This boundary will set up near the region, with several shortwaves tracking through the region, triggering two rounds of thunderstorms, one on Thursday and another on Saturday-Sunday. Thursday is expected to feature scattered afternoon-evening storms, although widespread severe weather is unlikely with marginal parameters.

Friday is expected to be drier with seasonable temperatures again, in the low-mid 80s, with a stronger wave of low pressure and cold front moving through on Saturday and Sunday. There is some uncertainty regarding the exact setup, although the overall idea is for a warm air mass to briefly surge into the region ahead of the low pressure resulting in slightly warmer temperatures on Saturday, with another cooler than average air mass entering the north central US behind the front. The model guidance varies with the timing, either Saturday evening or Sunday; at this time I am siding with a Saturday night frontal passage, although the timing is still subject to change. Widespread thunderstorms, possibly strong or severe, are likely to accompany the frontal passage, with cooler and drier conditions likely to return for the beginning of next week. Stay tuned for more information on next weekend’s outlook.

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