Tricky Forecast in the Works

Tue 7/1: It's been awhile since the last post to this section. Serious time constraints of late. Anyhow, with the holiday weekend quickly approaching, a discussion is in order - especially given the rather tricky, complex set-up that appears to be in the works.

A well defined cold front will drop southward through New York State and New England during the day on Thursday, reaching Southern New England Thursday Night. This front will be propelled southward by yet another polar vortex pinwheeling south through eastern Canada - a semi-permanent feature of the summer so far. Out ahead of this front, warm and humid air will feed a solid line of showers and thunderstorms over much of the Northeast later Thursday and Thursday night. A few of these storms will be strong to severe and some could survive the journey to the Cape, reaching our area Thursday night - though the best chance of seeing storms will be over interior sections.

At the same time heights are lowering over the Northeast in response to the jet stream digging down into the region, upper level heights will be trying to build over the Western Atlantic as some ridging tries to develop off the Southeast U.S. coast. In response to the digging trough and the building ridge, the upper level flow over New England will take on a southwest to northeast orientation. This spells trouble as it will slow the progress of Thursday's surface cold front and eventually cause it to stall out on Friday. Where this front stalls out will play an important role in the Friday through Monday forecast.

If the front were to clear the area completely and stall south of New England, we'd enjoy a sunny and warm, but less humid 4th of July weekend. Unfortunately, at the current time, that seems to be the least likely scenario as the front will lose "steam" as it drops southward. It is climatologically "normal" for these boundaries to hang up over the Northern Mid-Atlantic and Southern New England in early July. As such the more likely outcome is that the boundary stalls right near the South Coast of New England on Friday and gradually lifts back to the north and washes out with time over the course of the weekend.

Of course, with that front hung up nearby, the chances for periods of clouds and wet weather are higher from the 4th onward through the weekend. But the trouble, not surprisingly, is determining when these periods of showers and storms will happen as that will play a major role in just how we perceive the weekend weather - unsettled or not too bad. In other words, if we had numerous showers and storms and several inches of rain through the weekend, but it all occurred in the middle of each night, would anyone outside of the meteorology (or gardening?) community really care / notice? However, move that 8 to 12 hours in a different direction and you've got a completely different story.

So, that said, the forecast comes down to the exact placement of the front (which I would imagine oscillates north/south before lifting northward), timing individual energy centers riding along in the jet stream, factoring in pulses of warmth / moisture lifting northeastward and accounting for diurnally driven showers and storms. Given it is only Tuesday, this is not really within the realm of possibility. Looking at individual model precipitation outputs is also a waste of time, in my opinion, as they are just remarkably unreliable with specifics, especially in the mid to long range forecast period in the summer months as convection causes havoc with the outputs.

Overall, I think the extended forecast paints an accurate enough picture at the current time. That is, not a total washout of a weekend by any means, but the threat for scattered showers and storms, which could briefly interupt your outdoor plans. At this point, its not worth canceling anything, just check back for forecast updates.