We hope everyone enjoyed their Memorial Day weekend! Our weather transitioned from average temperatures and dry weather to warmth and humidity as a ridge built in. This weather is expected to persist for most of the rest of the week. However, a few shortwaves of energy may ride over the top of the ridge, which may drag a weak cold front near the area on Thursday. Considering the warm and humid airmass that is already in place, those triggers could be just enough to lead to some thunderstorms on Wednesday and Thursday, but particularly on Thursday.
In the meantime, the core of the ridge is on top of the area, with no ripples of energy to be found. This has led to mostly sunny skies, and warmth and humidity to spread into the region from the Gulf of Mexico. However, the core of the ridge can also lead to the seabreeze circulation cranking, which has kept coastal areas in the 70s. Inland areas are well into the 80s with even some 90-degree readings in some locations. Newark, NJ has hit a high of 91 degrees.
The area being in the core of the ridge and the seabreeze being able to eventually penetrate quite far inland should lead to enough sinking motion and stability to mitigate any thunderstorm threat this evening. It should be a nice late afternoon and evening, though some persistent breezy weather will continue.
The big ridge will move a bit to the east tomorrow, which may give the atmosphere a bit more room to trigger some thunderstorms.
The further west you are from the strong ridge, the better shot you have for air to lift throughout the entire atmosphere to produce some thunderstorms. This is why we may notice that this afternoon, areas well north and northwest of NYC may see some scattered thunderstorms.
Tomorrow, we will be in those area’s location, relative to the ridge. This means that the air in the middle of the atmosphere will be slightly cooler, which weakens the “lid” on the atmosphere for substantial lift.
Late tonight and early tomorrow morning could start off with some low clouds and fog, as the marine influence continues but without the sunshine and heat to burn it off. However, tomorrow looks to be another warm and humid day, as the sun will come out and quickly burn off any low clouds and fog. Seabreezes will be prevalent once again, which may lead to coastal areas staying in the upper 70s. NYC itself will be on the border of the strong seabreeze, so they should still hit the low to mid 80s, while most of NJ could hit the upper 80s to around 90.
As the ridge slowly moves east, a bit of troughing will move in. This should help to create a bit of lift in the atmosphere, though not necessarily widespread lift, since the main cold front will be off to the west. This will keep convection to a scattered level, for the most part.
However, the NAM (above image) shows CAPE values approaching 2500 J/KG — which is more than a sufficient amount of energy for thunderstorms. Also, precipitable water values will range from 1.4 to 1.8″, which indicates a plethora of moisture in the atmosphere. This combination should allow for some pulse strong convection to develop, with a few gusty winds and particularly heavy rainfall and flash flooding.
While wind shear doesn’t look strong in the above image, there will be decent wind shear a bit lower in the atmosphere as a mid-level jet passes by. This may allow thunderstorms to remain organized and even briefly approach severe levels. However, with the mid-level winds somewhat weak, storms may move slowly which could prevent them from remaining strong and severe for too long — though it would add more flooding problems. Additionally, with the seabreeze once again trying to penetrate inland, it may mean that thunderstorms weaken or even dissipate as they hit the I-95 corridor, as the seabreeze tends to stabilize the atmosphere. This means that the best threat for thunderstorms should be in E PA, N NJ, and the Hudson Valley.
If these storms do hang on to the coast (probably a 30-40% chance), then some heavy rainfall with flash flooding can be expected for NYC and parts of Long Island on Wednesday evening.
On Thursday, the shortwave will strengthen and come closer the region, thus the front will also. This means that winds will turn a bit more westerly, which may mean a bit less of a seabreeze influence, so storms could survive to the coast. However, the westerly flow behind the front may mean some dry air gets into the region before thunderstorms can truly develop. This could also mean that even coastal areas, as well as inland areas, could have some highs in the low to mid 80s, or warmer.
Thus, the best chance of thunderstorms may actually be in the late-morning and early afternoon, before drying out somewhat afterward. With a bit of dry air and more lift, some small hail is possible. If the front were to dissipate faster, then the better threat for storms could be on Wednesday evening and night, where moisture pooling will be quite efficient, but the front will also be somewhat close to the region.
On Friday, the dissipating front should stay just south of our area, meaning we will remain dry with sunny skies and less humidity. The next stronger cold front with thunderstorms looks to be on Saturday night into Sunday.