Severe Thunderstorm Watch South Jersey Severe Weather Risk Thursday
The arrival of warm tropical air into the region has created conditions favorable for severe thunderstorms tonight and a Severe Thunderstorm Watch is posted for Southern New Jersey and Southeast Pennsylvania southward into Northeast Virginia. The watch is in effect until midnight.
Radars both regionally and locally are showing a line of thunderstorms moving across Eastern Pennsylvania and there are some severe cells in this line. These thunderstorms are now moving into the watch area and be on the alert for warnings that could go up at anytime. The northern part of the line could move into Northern New Jersey in the next few hours though that part of the line looks less ominous at the moment.
LOCAL RADAR NEW YORK CITY
Thursday sets up for another round of severe weather and this could be more extensive. The Storm Prediction Center has upped the ante for Thursday adding an area of enhanced risk in Maryland, Delaware and Southern New Jersey with slight risk reaching up to just north of Route 195 in Central New Jersey. Marginal risk runs up into the Hudson Valley and Southern New England.
Depending on how much daytime heating we see tomorrow, there is a fair chance of seeing that slight risk area pushed further north and northeast. The tornado risk is unusually high especially in the enhanced area where there is a 10 percent chance of a tornado 25 miles within any point in the enhanced risk area with lower numbers elsewhere. 5 or 10 percent may not seem high but given the small scale nature of tornadoes it is a number we don’t see too often in these parts.
What is happening is that we have a cold front that is approaching but we also have a strong short wave trough that will be moving through and it will be combining with temperatures reaching the mid to upper 80s. Dew points Thursday will be in the range of 70 to 75 and that kind of juiced up air creates a very unstable atmosphere.
The Nam model shows the short wave trough at 10,000 ft very well with those dark orange and brown jet streaks moving through. This is indicating strong wind shear of 50 knots or higher in the darkest spots. This favors strong winds (downdrafts) at the surface and the possibility of some rotation developing in stronger cells (rotation).
Back the dew points, notice the area of 70 degree dew points reaches up to NYC and Long Island but it is in the area from Southern Pennsylvania to Southern New Jersey southward where we see dew points close to or even over 75. This is a very ripe atmosphere for a severe weather outbreak.
MANY THANKS TO TROPICAL TIDBITS FOR THE USE OF MAPS
Please note that with regards to any severe weather, tropical storms, or hurricanes, should a storm be threatening, please consult your local National Weather Service office or your local government officials about what action you should be taking to protect life and property.