Wild Monday Across the Northeast - Cape Should Escape the Worst of It.

MON 6/16: After a very nice day Saturday, clouds moved in Saturday night and brought periods of rain overnight and into the first half of Sunday. The good news is, we picked up some welcomed rain, with over a 1/2 inch reported at CapeCodWeather.Net. Obviously, the downside was a rather chilly and gray day with temperatures stuck in the upper 50s!

Sunday's cool, damp weather was actually the beginning of a new weather pattern, one that will last right through this week and possibly into the start of next weekend. The jet stream has sagged southward and an upper level storm center has developed north of the Great Lakes. Not only does this upper level storm center represent a pocket of cold air in the atmosphere, it is also helping to steer lobes of energy across the Great Lakes and through the Northeast. This overall set-up will last through the week, with the upper level storm only slowly drifting eastward during the course of the week - not all that different from what we saw back around Memorial Day, the week *before* the heat. This pattern, overall, favors cool temperatures and at least some unsettled weather at times. The worst of the weather looks like Monday and Tuesday, with slow improvement thereafter.

The combination of cold air aloft and energy rotating south and eastward with the upper level storm is helping to produce clouds and areas of showers and thunderstorms across the Northeast Monday. With such cold air aloft and a favorable jet stream, conditions are conducive for strong to severe thunderstorms (over interior sections where surface heating is maximized). This activity will fire over NY and PA ahead of a surface cold front and rotate eastward across New England later today and tonight. Strong winds, large hail and even a few cells capable of producing tornadoes are possible across a good portion of the interior Northeast.

However, while a widespread outbreak of severe weather is likely over NY and PA and perhaps into W. CT, MA and VT later today, this activity should gradually weaken as it works eastward into the more stable marine environment in eastern New England tonight. As opposed to surface temperatures well into the 70s to near 80F, this activity will encounter marine cooled air with temperatures in the 60s. So, after a very active afternoon and evening across much of the Northeast, reports of severe weather should drop off steadily later tonight.

Still, while the worst of the storms should be done this evening, prior to the activity ever reaching Cape Cod, just enough instability should be in place for a few lines of showers and storms to reach our area later tonight - just not nearly as intense as what is happening to the west. With this mind, don't be surprised to hear some thunder later tonight. A few heavy downpours are possible and if t-storms can survive, conditions will still be favorable for small hail thanks to the cold air aloft.