Scattered Severe T-Storms to Break the Heat Wednesday

A slight risk designation for severe thunderstorms has been issued for our entire area on Wednesday. Scattered thunderstorms will bring an end to our excessive heat. Several parts of New Jersey by late afternoon on Wednesday will reach 90 degrees or higher for the third day in a row, making this the first official heat wave of 2011.

The Storm Prediction Center has given us a high-end slight risk designation in the day two outlook. A 15% and 30% probability of severe weather warrants a slight risk of severe weather in the day two outlook. Much of New Jersey is under a 30% probability of severe weather occurring within 25 miles of a point. Most of the time when we are under a slight risk, we are placed within a 15% probability, so the threat is higher than normal at this time. Further evaluation will be done by the Storm Prediction Center on Wednesday Morning when we will be under the day one outlook which breaks the severe weather down by phenomena and gives a specific probability to each phenomenon.

While some large hail is possible, the main threat on Wednesday will be damaging wind gusts. The non-severe thunderstorm threats of dangerous cloud to ground lightning and brief torrential rains are likely with any thunderstorms.

Hot and Humid, T-Storms to Break The Heat

A heat advisory has been issued starting Monday at 12:00 PM EDT for Camden, Gloucester, Mercer, and Northwestern Burlington Counties. An excessive heat watch has been issued from Tuesday at 12:00 PM for Camden, Gloucester, Mercer, and Northwestern Burlington Counties through Wednesday Night.

For the advised and warned counties, heat indices will top out around 100 degrees for several hours on Memorial Day and around 105 degrees on both Tuesday and Wednesday. Temperatures will likely be around 92 to 95 degrees each day. The coastline could be a few degrees cooler with the cool ocean still influencing the beaches, but with a more southwesterly wind component, this may not happen on at least one of these days of the interior heat wave. While it will be equally hot in some of the counties not under an alert for heat, one must keep in mind that the criteria is lower in the urbanized areas due to the census data suggesting lower income around Trenton and Camden. Unfortunately, many in the alerted counties do not have access to air conditioning. Also, the temperatures drop slower in this area at night due to the urbanized environment as pavement doesn’t allow for ideal cooling.

Thunderstorm chances:

A shallow cold front on Monday will bring the chance for isolated pop-up thunderstorm activity. The models have been decreasing the chance for a thunderstorm after ratcheting it up on Saturday. Any thunderstorm that can form will have plenty of access to strong instability due to strong warming. The storms will not only have a poor focus, but they will also have to fight a cap that will be in place. Chance is about 20 to 30 percent.

Tuesday, heat and humidity related isolated thunderstorm. Chance is about 10 to 20 percent.

Wednesday, a strong cold front arrives to break the heat. This is the best chance of a thunderstorm of the next seven days. These thunderstorms have a decent shot of producing hail and strong winds, perhaps to severe limits. The chance of a thunderstorm is about 60 percent.

Chance of a Thunderstorm on Saturday

Tonight, there is still about a 30% chance of a thunderstorm in Northwestern New Jersey. Otherwise, the latest radar trends show that thunderstorms will mainly just miss this area unlike last night. Central Pennsylvania and Maryland is yet again getting quite a pounding...but these storms are not moving on as big of a northwest angle.

Thunderstorms are again possible on Saturday. The model guidance is suggesting that this will be the greatest threat over the past several days for thunderstorms and the chances are not all that high. There is a 40% chance of a thunderstorm tomorrow and this would include just about every location. Some isolated strong to severe thunderstorms will be possible if sufficient sunshine occurs.

Otherwise: heatwave begins on Sunday for some and lingers into next Wednesday. While there will be a 10 to 20% chance of a thunderstorm on Sunday through Tuesday with the heat and humidity...the best chance for a severe weather outbreak and widespread thunderstorms will be on Wednesday when a powerful cold front will bring an end to the heat and cool us off by about 10 to 15 degrees for Thursday.

More Severe T-Storms Possible Today, ESP. NW Again

Parts of Northwestern New Jersey into North-Central New Jersey will be spending the day evaluating the storm damage and cleaning up after powerful thunderstorms downed trees and produced hail up to the size of 1.50” in diameter.

Another day of thunderstorms, some severe, is expected, especially in the same areas that got pounded yesterday. There are a couple of reasons for the threat area being where it is. First, a stalled cold front has failed to make much eastward progress and while a bit further east today…it is not far enough east to shift the focus to the coast. Second, the southerly wind is bringing in oceanic air right along the eastern counties keeping temperatures several degrees cooler and the air more stable at the coast.

As mentioned…today’s front is a bit further to the east…so some a few isolated thunderstorms could make it a bit closer to the heart of the region later tonight and they could be severe with remaining instability. Yesterday’s thunderstorms got much further than the model guidance indicated and were much stronger, hence the problems in Northwestern New Jersey. Meanwhile, the edges of the area such as those in Hunterdon County will probably see late afternoon and evening thunderstorms that are potentially going to be severe.

Heatwave soon?

The cold front that was projected to be stalling across or just south of our region by the model guidance this week moved much further to the south, allowing for some pretty tranquil afternoons overall. We did have a few isolated thunderstorms on Tuesday. Today, we did not have any thunderstorms. We did have some cumulus clouds today.

The front will return as a warm front. As it does so, thunderstorms, isolated, are possible Thursday and Friday. The front will be driven by a low pressure center in the Great Lakes region (a familiar site this year) and it will drive a cold front towards New Jersey on Saturday and Sunday. The one problem is the front will never move through our region through Memorial Day weekend. Therefore, afternoon daytime heating could spark scattered showers and thunderstorms. It could also get quite hot ahead of the cold front, especially the latter half of Memorial Day weekend. It will not be until the middle of next week that a cold front actually swings through our region. It is possible that some areas see three consecutive days of 90 degree weather which means a heat-wave is not out of the question starting Sunday and lasting into Tuesday or Wednesday. This is considerably different from the model projections earlier in the week which showed the weekend cold front pushing offshore allowing for cooler air.

A week of thunderstorms

An onshore flow and a warm front to our west have really done a good job locking in the cooler in the eastern counties of New Jersey. Temperatures have been stuck in the middle and upper fifties in most of the eastern counties. Meanwhile, lower to mid sixties exist in the Central and Southern New Jersey interior. The onshore flow will not reverse itself until a stubborn warm front makes forward motion to the northeast. This will not happen until shortly after sunrise and therefore, fog could settle in for several areas until the wind shift happens. A northeast breeze or any scattered showers with the warm front may tend to keep the fog from become dense in some locations or widespread. But there is a chance of some thick fog in some areas if mixing relaxes.

The warm front should clear the southwestern areas of New Jersey first with the Central New Jersey counties following. There could be some sharp differences north and south of the frontal boundary. Clearing skies should follow the warm front passage and with the gates open for a southerly flow, a quick rebound in the temperature department is anticipated. The warm sector counties will at least approach 80 degrees, if not exceed it. Pieces of energy will ride along the warm front and since the front will be just north of our area, we will be affected by energy pieces. When disturbances ride along a warm front and you are directly south of it, it is typical for severe thunderstorms to develop. If we bake for a few hours, there is no doubt surface based instability will develop in the afternoon and linger through the evening. Storm coverage will be scattered. Damaging wind gusts, large hail, and even a tornado is all on the table.

A cold front approaches the region on Tuesday. However, any morning fog should give way to sunshine and a very warm and humid day. Mid to upper eighties can be expected. This will once again allow instability to increase and therefore thunderstorms and showers will develop in a pre-frontal trough in the afternoon and evening. The cold front approaching the warm sector and some waves on the front helping to energize it suggests another potential for severe thunderstorms. Some thunderstorms may produce heavy rainfall and localized flooding, especially with the rain from last week lowering the amounts needed for rain to begin to cause flash flooding and flooding.

On Tuesday Night through Thursday, the cold front stalls right over or just south of the region. Waves of energy will ride along the front and therefore showers and thunderstorms will possible throughout the entire period. The exact stalling point has not been determined. If some areas remain in caught in the warm sector, there will be an increased risk for stronger thunderstorm activity and they will also be more humid. But even right along and north of the front, thunderstorms on the strong and heavy side will be possible. Heavy rainfall is also a concern during this period as some thunderstorms could train over the same locations. Areas north of the front may see a reduced chance of storms and a nice day…maybe Thursday could be the day for that?

The stalled front then returns to the north as a warm front on Friday. Warm air advection showers and thunderstorms will be possible. A cold front will move through the region on Sunday and will be the trigger for showers and thunderstorms on Saturday and especially on Sunday. I wonder if this front will clear the region for Memorial Day. More severe weather and flooding concerns will exist during the weekend.

Thunderstorms This Afternoon and Tonight?

A backdoor cold front this afternoon and this evening will help to cause enough lift in the atmosphere for widely scattered showers and thunderstorms. Some of the higher resolution modeling is suggesting thunderstorms will be confined to Northern and North-Central New Jersey today. It is here where the best forcing will be located and it is reasonable to assume this is the highest threat area for convection.

However, there are a few higher resolution models that are suggesting activity region-wide. Given the past several days, the moisture content of the air, and the current temperatures: I think the activity will not just be confined to the North through the late afternoon and evening hours. Not everyone will see thunder and rain today, but some will.

I think the sea-breeze front will help to aid in the lift and cause some possible additional thunderstorm development. The radar is already showing the first signs of a sea breeze front, although convective temperatures have not been reached yet to spark t-storms.

Where thunderstorms form: Heavy rainfall, cloud to ground lightning, hail, and gusty winds will be possible.