Aug 12, 2012: Some Storms This Week

Forecast Highlights:

- Seasonable start to week ahead
- Isolated storms expected Tues/Weds, late week
- Moderate cool down possible next weekend

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Friday, August 10 Observations:

As a low pressure developed near southeast Michigan, widespread cloud cover was present across the region with areas of thunderstorms. The highlight of the day was a line of strong to severe storms that moved through in the late morning to early afternoon hours, producing widespread 1-2+ inches of rain for almost the entire area except for parts of NE NJ and NW NYC, which had very little rain. The severe storms, originally expected to be in the Mid Atlantic, unexpectedly affected Long Island and SE New England instead, with an EF-0 tornado confirmed in Suffolk county.

Temperatures on Friday were a bit cooler than Thursday, reaching the upper 70s inland and the lower to mid 80s across the rest of the area. The coolest high temperature was 75 degrees tied with Montgomery, NY and Sussex, NJ. The highest temperature was 87 degrees near Teterboro, although this temperature is interestingly several degrees higher than surrounding stations, even Newark which is typically the hot spot of the area.


Saturday, August 11 Observations:

Following Friday afternoon's storms, the overnight hours were generally dry across the region, although scattered storms were observed during the day, to the north/NE of NYC during the late morning and to the southwest of NYC during the evening. Temperatures were warmer than Friday, reaching the mid to upper 80s from NYC and further north/west and the lower to mid 80s in Long Island/S CT. The highest temperature was 89 degrees in Teterboro and Newark, with the coolest high 80 degrees in New London, CT.


Sunday - Wednesday: Seasonable, Some Storms

Following the departure of the Great Lakes low pressure from the region, mostly to partly sunny skies returned with temperatures reaching the mid to upper 80s from NYC and further north/west and the lower to mid 80s in Long Island/S CT. Similar temperatures are expected to continue for Monday, slightly warmer on Tuesday with more widespread upper 80s from NYC and further north/west, with some spots reaching and/or slightly exceeding 90 degrees. Cloud cover will increase on Tuesday as a weak low pressure approaches the region, producing scattered thunderstorms especially late in the day and into the overnight hours. Isolated/scattered storms will continue on Wednesday with slightly cooler temperatures, reaching the lower to mid 80s across the area. A few storms may be strong or severe, although no widespread thunderstorm/severe weather event is expected.


Thursday - Beyond: More Showers/Storms, Cooler Temps

By the late week into next weekend, the Greenland ridging that was entirely missing during the winter yet frequent during the summer months will make its return, as a strong 576 dm ridge builds into Greenland while cold from a strong polar vortex over Canada spills south towards the central US, bringing much cooler temperatures into areas that were hit hard by heat and drought this year. A cold front will make its way further east while the strong trough drops into the north central US, where widespread low temperatures in the 40s and even some 30s are expected. With the cold front moving east, rain and thunderstorms will make their way into the region by Friday further west and Saturday further east along with the potential for some severe thunderstorms. The GFS is currently the most progressive with the cold front, while the ECM and CMC are slower; given the trough axis focusing over the central US with blocking to its east over Greenland, the front will slow down as it reaches the eastern US, and I am siding with the slower ECM/CMC solutions for this time frame, with widespread showers and thunderstorms persisting on Saturday and into at least parts of Sunday.

Temperatures will reach the lower to mid 80s across the area, slightly higher in the immediate NYC area, on Thursday, with warmer temperatures for Friday in the mid to upper 80s from NYC and further north/west. Highs in the lower to mid 80s are expected again for Saturday and Sunday, perhaps staying below 80 degrees in some areas. The coolest temperatures will stay west of the region; with the front slow to exit the region, what's left of the cool air mass will be moderated by the time it reaches the area, with temperatures likely peaking in the upper 70s to mid 80s across the area for a short time behind the cold front, towards early next week, with drier conditions. The pattern until now has consisted of ridging in the western Atlantic and near the central US, resulting in slightly lower heights in the Northeast although there is more of an influence from the western Atlantic ridging, as seen with the lack of strong heat but frequent humidity and thunderstorm events. Although the trough is expected to weaken going into the middle of next week, no strong ridging is expected to build in accordingly with the pattern, with temperatures likely remaining close to average, somewhere around the lower to mid 80s range.