My Personal Weatherman™
***Latest info on the strong to severe thunderstorms for this evening***
- The 1st and 2nd images show the future radar for 8 PM and 9 PM, and the 3rd and 4th images are from NWS NY and NWS Boston. Heavy downpours, frequent lightning, hail, damaging wind gusts up to 60 mph, and even a tornado are all in play.
- Here is a very interesting discussion from NWS NY covering Long Island and the tri-state area:
Attention then turns to the aforementioned upper low/trough and the associated cold front poised to sweep across the region this evening. Along and just ahead of the front and upper low will be a strongly forced low-topped line of convection. This convection will be working its way across upstate NY and PA in the afternoon and then should be nearing the Lower Hudson Valley 21-23z, and over the NYC metro/Hudson River Corridor 23-01z. The line then encounters the stronger maritime influence and should weaken as it moves across central/eastern LI and CT 01-03z. As is usually the case in our area with convection, the amount of instability is still uncertain. Some of the CAMs indicate 500-1000 J/kg of MLCAPE that develops in the afternoon from the NYC metro on N and W. Other CAMs indicate lower CAPE values. Confidence is much higher in there being a tremendous amount of unidirectional shear. These low CAPE high shear environments can cause convection to struggle to organize to severe levels. The strong forcing from the upper low in this case may help with updraft organization moreso than what we see later in the warm season in similar low CAPE high shear environments. While there may be some instability further east in the maritime influence, it may be elevated so the concern for severe weather is lower here. SPC has continued to place most of the area in a slight risk for severe weather. The primary threat is damaging wind gusts in excess of 58 mph hour. Large hail is also a threat, mainly west of the NYC metro as the higher CAPE may couple with the colder air aloft from the upper low. These threats are more limited east of the NYC metro and SW CT in the maritime environment. However, small hail cannot be ruled out anywhere given the cold pocket aloft. Another concern that will need to be watched is some CAMs continue to back the low level flow immediately ahead of the front, increasing helicity. There is a 5 percent chance of a tornadic development in NE NJ with a 2 percent risk in the Lower Hudson Valley and NYC metro and SW CT. As noted in the previous discussion, there are lots of conditional probabilities with this event. Should the ingredients all line up, a squall line with some discrete rotating cells is a possibility. As for non-thunderstorm winds, pre and post-frontal gusts could reach 35-40 mph, especially away from the coast this afternoon ahead of the front. Think gusts will be held down a but further east due to a stronger inversion. Mixing looks much stronger behind the cold front passage Saturday evening and night. Gusts immediately behind the front could reach 40-45 mph, with some isolated gusts to 50 mph. The chance of this is brief and if it were to occur would be immediately behind the front, with gusts remaining 30-40 mph for the rest of the night. No wind advisory has been issued at this time.