May 21, 2011 Morning: Update On Next Week

Note: As there are significant changes taking place with the forecast, this discussion was updated on Saturday morning to discuss these changes in more details. The 5-Day Forecast will be updated this afternoon to reflect the changes as well.

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The upper level low that has been stuck over the region for almost a week, bringing widespread rain and thunderstorms, moved over the area yesterday as it slowly started to leave the region. Originally, it appeared that yesterday would bring a strong thunderstorm risk, but with the upper level low right above the area, other than a few showers most of the area stayed dry, with strong to severe thunderstorms to the north, south and west of the area, rotating counterclockwise around the low.

With the upper level low finally exiting the region, much nicer conditions will return for this weekend, other than the risk of isolated thunderstorms this afternoon, especially northeast of NYC, with partly sunny skies and high temperatures in the 60s and 70s. These conditions will be brief, however, as an approaching cold front and warm air mass for next week bring warmer temperatures as well as the risk for thunderstorms in parts of the week.

Weekend Outlook:

With the upper level low moving out of the region, today will bring clearing skies to the area, with partly sunny skies expected. The low will still be capable of producing isolated showers and thunderstorms this afternoon, especially north and NE of NYC towards SE New York, Long Island and southern Connecticut, and while a few of these storms may become strong, these storms are likely to stay below severe levels and will not be as widespread or as strong as the storms today and yesterday in the region.

Warmer temperatures are expected today as well, reaching the lower 60s to lower 70s for Long Island and southern Connecticut, and the mid to upper 70s from NYC and further west. While not modeled at this time, parts of NJ may reach the 80 degree mark, but this should stay to the south/SW of NYC.

Sunday will bring colder temperatures as a high pressure moves south off the coast, bringing an onshore wind into the area. Places west of NYC should not be affected as much, with highs in the upper 60s to mid 70s, with mid 60s expected in NYC, but Long Island and southern Connecticut will see much colder temperatures, expected to only reach the lower 50s to lower 60s.

Next Week: Warmer Temperatures Return, Some Storms

Over the last day, significant changes have been taking place with the expected scenario, and it no longer appears that there is a major warm up or a significant severe weather outbreak headed towards the region on Tuesday.

Originally, a low pressure was expected to move slowly through southern Canada on Monday/Tuesday, slowly bringing in a warm air mass on Monday with partly sunny skies and highs in the mid 70s to lower 80s from NYC and further west and bringing severe weather on Tuesday as the cold front approaches the area. This scenario is no longer favored, however, as a cold air mass in Canada is expected to push towards the area more than originally modeled, and with the storm moving faster, Monday will be the day that brings widespread thunderstorms, some strong, to the region, with the cold front already moving through the area by Tuesday afternoon.

Monday: With a high pressure still offshore on Monday, an onshore wind is expected for places east of NYC, including NYC, with the warm front likely to be placed near NYC during the afternoon. As a result, high temperatures are likely to be in the upper 60s to mid 70s for NYC, lower to upper 70s west of NYC, and the mid 50s to mid 60s east of NYC. There is still some slight uncertainty, and these temperatures are subject to slight changes. As the cold front approaches the region from the west, widespread showers and thunderstorms are expected, especially in the afternoon and evening hours. With supportive parameters, some of these storms will be strong or severe, especially towards Pennsylvania, western NY, and the rest of the central/southern Mid Atlantic. As NYC should be near the edge of the warm sector, thunderstorms are expected from NYC and further west, potentially strong, but the best risk of severe weather exists to the west of the area.

Tuesday: The cold front is expected to move through on Tuesday, bringing mainly dry conditions, though scattered showers and thunderstorms, potentially strong, are still possible. With a west/WSW wind expected along with partly cloudy skies, warmer temperatures will return, reaching the lower to mid 80s across most of the area, even including Long Island and southern Connecticut away from the coast. The warmest temperatures will be in the immediate NYC area, where mid 80s are expected. With the front nearby, however, temperatures are unlikely to get much warmer than the mid 80s, and this will also prevent the originally expected severe weather outbreak from taking place, instead bringing a risk of scattered showers and thunderstorms.

Late Week: The cold front from Tuesday is expected to stall on Wednesday and potentially Thursday near the area. Should this scenario take place, it would bring drier conditions for Wednesday along with colder temperatures, reaching the 70s in NYC and further west. The 06z GFS shows a severe weather outbreak on Wednesday, however at this time this scenario is an outlier. By Thursday and Friday, a storm to the west of the region, potentially a cut off low, may bring a warmer air mass into the area again as well as a severe weather risk, but as this is in the longer range, details may change. Stay tuned for more information on next week and the Memorial Day weekend with tonight’s update.

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