Sunshine to Increase from South to North, T-Storm Risk Remains

All of New Jersey remains under a slight risk for severe thunderstorms this afternoon and this evening by the Storm Prediction Center.

The risk for damaging winds is the primary risk, although the hail parameter guidance I use does suggest the potential for marginally severe hail.

We see very good sunshine breaking our within the warm sector in Southern New Jersey and I suspect this will lift northward throughout the afternoon, although some cloudiness from the west may tend to make things partly sunny when the sun breaks out for the remainder of Central and Southern New Jersey. The guidance continues to suggest a 20-30 degree temperature rise within a couple of hours which would drastically increase the instability needed for strong to severe thunderstorm initiation.

However, despite the given instability, there are STILL legitimate questions about whether there will be really a breakout of severe thunderstorms. Yes, we have a cold front which will act as a triggering mechanism to initiate thunderstorms. But the North American model and Global Forecast System model show weak convergence and lacks well organized and widespread thunderstorm initiation. In fact, the 12z NAM agrees with the previous two runs of the model and shows 0.00” of measurable precipitation in just about the entire New Jersey area.

So, this leads me to the forecast for the event. Thunderstorms will be isolated to scattered in nature. Due to the instability, where they develop, they could quickly become severe with the potential for damaging winds and possible hail. The higher resolution modeling is a bit more robust with the development of thunderstorms for this afternoon across our region...but even these models have trended towards scattered development. At this present time, I am leaning with the modeling indicating less explosive and widespread development. This does not mean we will not have some pretty significant events with notable damage, it just means some areas could be bone dry and cloudy while others are getting hammered just 20 miles from where you reside.

Slight Risk for Severe T-Storm Wednesday, But Will They Form?

For Wednesday, the Storm Prediction Center has placed our entire region under a slight risk for severe thunderstorms. In fact, the Storm Prediction Center has a high-end slight risk probability with a 30% chance for severe weather to occur within 25 miles of a point. Certainly the instability will be there tomorrow. Sunshine should develop by mid-morning and temperatures will quickly push well into the seventies as we will be in the warm sector of a warm front that will be lifting northward early this morning. Some of the more robust guidance even indicates some lower eighties across South Jersey. This will lead to CAPE values of 1,000 to 2,000 j/kg. The lifted index also may be at least -3, if not higher.

However, despite the given instability, there are legitimate questions about whether there will be really a breakout of severe thunderstorms. Yes, we have a cold front which will act as a triggering mechanism to initiate thunderstorms. But the North American model and Global Forecast System model show weak convergence and lacks well organized and widespread thunderstorm initiation. In fact, the 00z NAM shows 0.00” of measurable precipitation in just about the entire New Jersey area.

So, this leads me to the forecast for the event. Thunderstorms will be isolated to scattered in nature. Due to the instability, where they develop, they could quickly become severe with the potential for damaging winds. The higher resolution modeling is a bit more robust with the development of thunderstorms for tomorrow afternoon across our region. At this present time, I am leaning with the modeling indicating less explosive and widespread development. This does not mean we will not have some pretty significant events with notable damage, it just means some areas could be bone dry and cloudy while others are getting hammered just 20 miles from where you reside.

Showers and T-Storms Today

Frequent periods of showers and thunderstorms will affect the region today. Showers with a few thunderstorms are already moving in from the west along our nearly stationary cold front... which will eventually become a warm front and lift northward.

There will be quite a contrast from north to south today as the front will set up a dividing line. With the eventual warm front close to the warm sector and these waves riding along them, some strong to severe thunderstorms, isolated in nature, have the chance to form immediately south of the front while areas along and north of it will just see general showers and thunderstorms. 0.25" to 0.50"+ of rain appears likely still for the region with some localized higher amounts in thunderstorms.

Tonight I will discuss the potential for severe thunderstorms on Wednesday. The Storm Prediction Center has placed our area under a slight risk for severe thunderstorms on Wednesday.

Showers and Thunderstorms Tuesday & Wednesday

A cold front will meander around the region on Tuesday and then go into reverse as a warm front. During the transition process, a few waves of low pressure will be riding along the front providing plenty of clouds with showers and thunderstorms. Southern areas could be quite warmer than northern areas with it very dependent on which side of the front you reside on. This front may also allow for some severe convection on in the warmer sector as the waves ride along the frontal boundary.

On Wednesday, a cold front will come into the region. The models are not all that robust with the afternoon and evening t-storm potential, but with the region potentially all in the warm sector and an approaching trigger...some severe thunderstorms are possible...even if not widespread.

With many waterways near flood stage and running high, 0.50" inches of rain may pose some problems and certainly any heavier thunderstorms would be of great concern.

Isolated Gusty T-Storms North Into This Evening Possible

The Storm Prediction Center has placed the northern half of New Jersey, including portions of North-Central New Jersey under a "see text" risk for severe thunderstorms and all of North/Central New Jersey in a general risk for thunderstorms.

A disturbance will take advantage of steep lapse rates to develop some showers and potentially a few isolated thunderstorms. I already see some showers developing downwind of the Great Lakes...moving on eastward. If they survive...they would arrive late this afternoon into early this evening...before losing daytime heating support. With stronger winds aloft (some observed already by good mixing with surface gusts to 40 MPH)...any t-storm may be able to tap into this a cause some marginally severe gusts.

At this time, I am keeping the threat isolated. CAPE values look very limited at this point and may develop slightly by 4 p.m. to coincide with the arrival of the disturbance.

Flooding:

Yesterday's rain really did a number on the region and this storm really lived up to the potential I had been forecasting. Major flooding once again is ongoing in Northern New Jersey with moderate flooding in portions of Central New Jersey. The windy conditions today are also combining with the wet ground and I have had a few reports of power outages.

Coastal Flooding:

Still a threat of minor to moderate tidal flooding for the next few high tide cycles along the tidal portions of the Delaware River in Southern New Jersey.

Major Storm: Numerous Flood Warnings, Near-Record Flooding Near Philadelphia

Just after 10:50 p.m., the National Weather Service issued a special weather statement regarding near-record, major tidal flooding in addition to the coastal flood warning...

At Philadelphia, high tide occurs at 1:12 a.m. with a forecast high-tide level 10.5 feet above mean lower low water. The last time the tide level reached 10 feet at Philadelphia was on December 11, 1992.

The record level is 10.8 feet which occured on November 25, 1950. The National Weather Service expects severe flooding according to the statement and is advising all residents along the tidal areas to pay close attention to rising waters.

At this hour, nearly every county in our coverage area has been placed under a flood warning due to the excessive rainfall. Flooding is especially dangerous at night...turn around and don't drown.

Tornado Watch for Southwestern New Jersey Thus Far

Thunderstorm Wind Gusts to 70 MPH, Isolated Tornadoes, and Hail to 0.50” in diameter are possible in the watch area.

A tornado watch means conditions are favorable for the development of tornadoes, damaging winds, and or large hail.

Strong pressure falls are becoming clearly visible over Eastern Pennsylvania and Western New Jersey. I wouldn’t be surprised to see this shift northeastward throughout the evening. Without sunshine today, instability is modest at best. However, the jet setting up over the region and heavy thunderstorms will move in from the west and drag the strong winds to the surface with an increased risk for damaging wind gusts. In addition, vertical shear is quite impressive and the strongest thunderstorms may cause some spin-ups which may result in isolated tornado development in our region. Numerous severe thunderstorm warnings and tornado warnings have occurred to our south and west.