Cold Front to Bring Relief From Heat/Humidity and Much Needed Rain

The high heat and humidity is set to come to an end as a cold front slowly progresses towards New England late Wednesday and on Thursday.  As the cold front traverses New England, the front is expected to stall across the region.  As this occurs, weak waves of low pressure are expected to develop and rid up along the cold front.  The presence of the stalled front overhead along with areas of weak low pressure riding up along the front will set the stage for numerous periods of showers and thunderstorms and some of the rains will be quite heavy.  Once the cold front passes the region, we will see much more seasonable temperatures and humidity levels filter in.

Moving through the remainder of Wednesday, as of 4:00 PM EDT, the cold front was slowly pushing through western and central New York state where a broken line of showers and thunderstorms have developed, including a few strong to severe thunderstorms.  As this front continues to slowly slide south and east, the risk for showers and perhaps some thunderstorms will increase as we work through the evening and into the overnight hours.  With very weak shear aloft, poor mid-level lapse rates, and instability expected to wane with loss of dayitme heating, the risk for strong to severe thunderstorms will be very low.  The main threat would be for torrential downpours.  However, gusty winds can't be ruled out.

On Thursday, clouds will be present region wide, holding back temperatures more closer to 80F rather than 90F, however, the humidity will still be pretty high with dewpoints right around 70F.  While it will be cooler, it will still be quite humid.  Mid-level lapse rates will be continued weak with weak shear in place as well.  While thunderstorms will be possible given the presence of weak instability thanks to very moist low-level airmass, the above factors indicate the threat for strong to severe t'storms will be very low.

For widespread heavy rainfall, it would be beneficial to see a much stronger low-level jet forecasted, however, that is not the case here.  Computer forecast models though are indicating PWAT values as high as 2'' throughout the day on Thursday, a very strong indicator of how moist the airmass will be.  With multiple waves of low pressure developing, presence of weak instability, and moist airmass, we will see periods of showers and thunderstorms throughout the day tomorrow.

As far as rainfall totals go, computer forecast guidance is suggesting anywhere from 1''-2'' of rainfall would be possible.  Looking at the SREF forecast model below, (a compilation of numerous pieces of numerical guidance to generate an average) it seems like a good bet most folks can expect anywhere from 0.50'' to 0.75'' of rain.  However, there will be some locations who potentially exceed 1.50'' to 2'' of rainfall tomorrow.