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John Homenuk

Heat and severe storms Wednesday, Arthur late week

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UPDATE 2:00pm: A severe thunderstorm watch is in effect until 9:00pm this evening. The Storm Prediction Center suggests severe thunderstorms are possible, capable of producing strong winds, small hail, and dangerous lightning. Stay tuned for updates including any severe thunderstorm or flood related warnings. The latest information on the severe thunderstorm watch can be found here.

Heat Advisories were issued by the National Weather Service for much of New Jersey on Wednesday, as heat is expected to build throughout the area once again. Rising dew points are only adding to the issue — as they will create a much muggier, more oppressive airmass than the past few days this week. Heat index values are expected to rise well into the 90’s and possibly come close to 100 in some spots later this afternoon. Any time dew points rise into the mid 70’s while temperatures are in the mid 90’s — the air will be quite heavy.

In addition to the oppressive heat, strong to severe thunderstorms are possible this afternoon. The Storm Prediction Center has placed the area in a “Slight Risk” for severe thunderstorms, indicating a risk of small hail and strong winds. In addition to those threats, heavy rain and frequent lightning would be likely in any thunderstorms that develop. We encourage you to stay tuned throughout the day for updates on the developing thunderstorms and hazardous weather threat. In addition, stay hydrated and avoid prolonged outdoor exposure.

Day 1 Outlook from the SPC showing a Slight Risk throughout the area on Wednesday.

Day 1 Outlook from the SPC showing a Slight Risk throughout the area on Wednesday.

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John Homenuk

SPC issues rare High Risk over Great Lakes, Ohio Valley

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A major severe weather outbreak is forecast this afternoon across much of the Great Lakes and Ohio and Mississippi Valleys. The Storm Prediction Center has issued a rare “High Risk” for severe weather across much of Illinois and Indiana as well as parts of Southern Michigan and Western Ohio. A highly unstable atmosphere, juxtaposed with an impressive storm system both aloft and at the surface, will act to trigger the development of impressive late-season severe thunderstorms. Impressive low level shear and wind turning will allow for the potential of widespread tornadoes, some of which could be violent. With time, the storms will organize to pose more of a damaging wind threat as they shift eastward towards the Ohio Valley. For more on the developing threat, stay tuned to the Storm Prediction Center page which will display all outlooks, watches and warnings.

In our area, the SPC has extended a “Slight Risk” for severe weather to include all of New Jersey, New York and Connecticut. As the associated cold front sweeps through the Ohio Valley and eventually the Northeast US later today, the potential for isolated strong wind gusts is expected to continue. The threat, and intensity of the storms, is not expected to be nearly as severe as it will be back across the Great Lakes and Ohio Valley.

Storm Prediction Center Day 1 Categorical severe weather outlook from 11/17/13, showing a High Risk over parts of IL, IN and OH as well as a Slight Risk in the NYC Area.

Storm Prediction Center Day 1 Categorical severe weather outlook from 11/17/13, showing a High Risk over parts of IL, IN and OH as well as a Slight Risk in the NYC Area.

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Update: Slight Risk of severe storms from SPC

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The Storm Prediction Center has placed parts of Northern New Jersey, Southeast New York ,Connecticut, and the New York City Metro Area in a “Slight Risk” for severe thunderstorms Wednesday afternoon and evening. The “Slight Risk” category is triggered by probabilities of severe weather within 25 miles of a point — and in this case the SPC indicates a 15%-30% chance of severe storms within 25 miles of any point in that area.

Scattered thunderstorms are expected to develop over Pennsylvania and New York later this afternoon before moving into Western New England and Southeast New York. The storms may then eventually drop south and east towards Northern NJ and New York City. However, confidence is higher in the potential for storms to the north of our area. Here, better shear and instability parameters are juxtaposed to support organized severe thunderstorm potential. One forecast model, run for the Storm Prediction Center, suggests the storms may move farther south — into Northern NJ and NYC ( see below ).

SPC-WRF model, forecasting strong thunderstorms impacting the NYC Area Wednesday evening.

SPC-WRF model, forecasting strong thunderstorms impacting the NYC Area Wednesday evening.

After a warm front passed the area this morning, southwesterly winds ushered in a much warmer and more humid airmass. So, the potential exists for the strong storms to move into the NYC Area later this evening despite the fact that the better support for severe weather remains to the north.

Stay tuned for updates on potential watches and warnings from the National Weather Service through the afternoon (this post will be updated).

Damp Tuesday, but big warmup en route

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Warm fronts can be pretty deceiving. Depending on the positioning of the front at the surface, and the amount of warm air that looms behind the front, conditions can seem fairly raw and damp near and ahead it. Much of the same is true in our area today, as east winds ahead of a surface warm front to our south along with a weak low pressure system riding along the front itself will provide cooler conditions and periods of rain.

Waiting behind the front, which will pass the area early Wednesday, is a surge of warm air. Temperatures at the 850mb level will rise from around 8-9 C Tuesday morning, to 15-16 C by Wednesday — and even warmer on Thursday. At the surface, highs in the 60’s on Tuesday with clouds will rapidly rise into the upper 80’s and lower 90’s later this week. In addition, a westerly wind component should help the warmth get all the way to the coast — and limit the inland extent of the seabreeze.

Showers and storms, however, will linger through Wednesday before the heat arrives. In fact, the Storm Prediction Center suggests a small chance (5-15%) of a severe thunderstorm in the area as the warm front passes on Wednesday. Stay tuned for further updates. Their probabilistic outlook, shown below, suggests the best chance for severe thunderstorms will be farther north — where the warm front will be Wednesday afternoon. A slight chance of storms capable of producing gusty winds exists as far south as New Jersey.

Storm Prediction Center Day 2 Outlook, valid for May 29th, 2013. The probability of any severe weather within 25 miles of a point is shown. A 15% probability (yellow) triggers a "Slight Risk" of severe weather.

Storm Prediction Center Day 2 Outlook, valid for May 29th, 2013. The probability of any severe weather within 25 miles of a point is shown. A 15% probability (yellow) triggers a “Slight Risk” of severe weather.

Stay tuned for further updates on not only the potential for storms, but the impending warmup and warm frontal passage on Wednesday. You can follow our social media accounts on Facebook and Twitter for more frequent updates and posts throughout each day.