A deep southwesterly flow, will transport a very warm and humid airmass today with clouds mixing with some sunshine. High temperatures today will depend on the amount of cloud cover. Areas that see more sunshine, could get make run at 90 degrees or higher today. More clouds than sun, highs will be in lower to middle 80s. The forecast highs will compromise between middle to upper 80s. Except near the shore, a southerly winds likely keep high temperatures in lower to middle 80s. A surface trough and shortwave trough (upper-level disturbance) will trigger numerous showers and thunderstorms across the region late this afternoon and tonight.

Models show anywhere between 1000 J/kG and 2000 J/kg of MLCAPE with 25kt to 35kts of shear this afternoon and early this evening. This will support some thunderstorms to become strong to severe with damaging winds being the main threat. Some backing of the low-level winds this afternoon, could support an isolated, weak tornado. Especially over Northern NJ and Lower Hudson Valley. Some hail is also possible out thunderstorms. But threat for large hail is reduced somewhat with high freezing and wet-bulb zero levels. Inhibiting factors for severe weather today, are weak mid-level lapse rates and some cloud cover keeping surface-based instability from reaching extremely high levels. Also with winds more out the south this afternoon, areas near the coast will be more stable and this may cause thunderstorms to weaken. Which is why the Storm Prediction Center has the 15% slight risk northwest of NYC. Overall I’m expecting any severe weather reports to be isolated to scattered across to the region.

More likely than the severe weather, is potential for heavy rainfall out of thunderstorms late this afternoon and tonight with pwats (precipitable water values) near or over 2.00″.  With mostly unidirectional shear, some of training of storms with flash flooding possible in  low-lying or poor drainage areas. Depending how showers and thunderstorms setup some places could receive less than .50″ rainfall to locally one to three inches of rain.

That all being said, it is not necessary to cancel plans. It will be dry, until late this afternoon for most areas and perhaps until early this evening for coastal areas. If you are at beach, park,pool, etc, be prepared to move indoor as quickly as possible, if a thunderstorm hits. Any thunderstorm whether severe or not, can produce dangerous cloud to ground lightning. Don’t take shelter under trees, as they are huge conductors of electricity. Tomorrow (Labor Day) will continue very warm and humid with mixture of sunshine and clouds. More scattered showers and thunderstorm will still be threat all day tomorrow. As the shortwave trough lingers over the area. Pwats still over 2.00″ will  support heavy rainfall out of any thunderstorm tomorrow. However, with move convective debris or clouds, this will likely keep instability lower. On Tuesday, surface high pressure will build briefly more sunshine. A deep southwesterly flow with 850mb temperatures around 18C will help temperatures rise into the lower 90s, away from the coast. A cold front and upper-level trough approaching from the west will trigger more showers and thunderstorms by Tuesday night.

Check the latest Tri-State 7-day forecast details and summary for more updates for today’s severe threat threat.

Also follow @WeathergunNY for any watches and warnings later this afternoon and night.

Have a nice Labor Day weekend!