May 29, 2011: Summer Begins In NYC Area

Note: The 5-Day Forecast will be updated tomorrow morning, and an update discussing tomorrow’s conditions and Wednesday’s severe weather will be posted as well.

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With a very warm air mass starting to spread into the region from the south central US, today brought warm temperatures into the area, reaching the lower to mid 80s from NYC and further west, and the lower to upper 70s in Long Island and southern Connecticut with a few lower 80s reported as well.

June 1st is the start of meteorological summer, and this year’s June 1st will feel like a typical July day. Hot temperatures will enter the area tomorrow, bringing high temperatures into the 90s from NYC and further west, and while temperatures will cool down from NYC and further east on Tuesday due to a weak back door cold front, Wednesday will slightly warm up ahead of a cold front, which may be capable of producing the area’s first significant severe weather outbreak of the year.

Memorial Day Outlook: Hot And Humid

**Correction: The date on the graphic should be “5/30”, not “5/29”.**

A very warm air mass will move into the area tomorrow, with 850 mb temperatures near 20 degrees celsisus. Other than some fog and cloud cover in the morning, clearing skies are expected by the afternoon, which combined with a southwest wind, will allow temperatures to rise into the 90s from NYC and further west. Most areas west of NYC will reach the lower 90s, but some mid 90s are expected as well in parts of the immediate NYC area. Heat index may reach the mid to upper 90s in the immediate NYC area. East of NYC, warm temperatures are expected as well, ranging from the mid-upper 70s along the immediate coast of Long Island to the upper 80s in western Long Island/SW Connecticut.

There is some slight uncertainty with the exact temperatures, and at this time I am going slightly warmer than the model guidance. In addition, there is also the risk of pop up showers and thunderstorms late tomorrow afternoon into the evening hours, and while the storms that do form, if any, should be isolated, any storm that does form may be capable of reaching strong/severe levels. An update will be posted tomorrow morning regarding tomorrow’s conditions as well as Wednesday’s potential severe weather outbreak.

Tuesday – Thursday: Heat Continues, Severe Weather Risk

A weak back door cold front will move into the area on Tuesday morning, moving in from north to south. This will result in a mostly east wind for the central and eastern parts of the area, bringing in colder temperatures. Temperatures from NYC and further west will still be very warm, in the upper 80s to lower 90s in northern NJ and in the mid to potentially upper 80s in NYC, but east of NYC, temperatures will be colder, reaching the lower 70s to lower 80s. Some models have been suggesting a risk of severe weather on Tuesday, and while it is uncertain at this time, isolated showers and thunderstorms cannot be ruled out, some which may be strong.

As a storm well to the north of the area moves east, the back door cold front will move east again as a warm front, with 850 mb temperatures once again returning into the 18c-20c range. Some sunshine is expected through the afternoon hours, allowing temperatures to warm up once again into the upper 80s to lower 90s from NYC and further west with a southwest wind, bringing warmer temperatures to Long Island/southern Connecticut as well.

Severe Weather Risk: By the late afternoon hours, however, the storm’s cold front will approach the area, bringing widespread showers and thunderstorms into the Northeast, generally moving east/ESE. The models are showing extremely high parameters, with the GFS showing CAPE as high as 4000 and LI as low as -12, which can cause large scale severe weather outbreaks if the right conditions are in place. There is a lack of bulk shear, however, which is only expected to reach 30-35 knots. In comparison, the severe storms in Pennsylvania several days ago were generally in the 40-60 knot range.
Regardless of the lack of bulk shear, this cold front is still capable of producing a widespread significant severe weather outbreak. SPC, the Storm Prediction Center, has also noted this potential, starting to do so yesterday by placing a rare Day 5 severe weather risk in the area. At this time, I would place a 30% risk of severe weather in the area, however some changes are still possible. Stay tuned for more information on this severe weather event.
Longer Range: Thursday will still bring temperatures in the mid 70s to mid 80s across the area, but by Friday, a cold air mass will move through. The models have backed away from the significant cold that was shown several days ago, and are now expecting temperatures to mostly drop into the mid 70s to lower 80s across the area for Friday. Next weekend will bring more widespread 80s into the area once again as warmth builds into the region once again.

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