There's been a good amount of discussion over the past few days regarding the potential storm threat later this week. Although many times these systems are blown out of proportion (over-hyped/etc), I feel comfortable saying that this one has some credence to it. There's a very large upper level trough that cuts through the MS/OH Valley's and the northern stream is extremely active as it races southeast towards the Great Lakes. Should the northern stream energy phase with the trough over the OH Valley, the translation to the surface could be rather impressive; with a deepening surface low getting yanked back northwest and captured by the upper level feature, also resulting in the development of heavy precipitation over New England.

The real problem with the storm threat is the Northern Stream energy, and unless this phases in with the main trough as the GFS had advertised several times over the past few days, we are not going to get the rapid deepening at a fair enough latitude for us to receive anything noteworthy. Eventually, once the trough reaches a certain latitude, that northern stream energy will phase into it; but we need it occur further south in order to
 get the rapidly deepening surface low over New England or more likely in the Gulf of Maine. I've included an image of last nights 00z GFS and the latest GFS to help illustrate the differences. The screenshot to the left has only one feature circled, the northern stream energy already phasing into the trough and racing southeast towards the trough base. This is already an extremely dynamic set up which, once the s/w reaches the trough base and PVA begins, will translate to the surface. To the right is the latest Operational GFS, which has two features highlighted; in blue is the ridge axis cutting off the phase of the upper level trough with the s/w energy and in pink is the s/w energy that was much further south and partially phased into the trough by the same valid hour on the 00z run. The result is a weaker surface reflection on the latest GFS, the surface low doesn't really deepen until it's well northeast and out of the picture of our sensible weather.

This afternoons ECMWF has trended a bit towards the more amplified solution, which should be a bit alarming for those to our north in New England (especially those in the interior, this could be a great early season storm for the ski/snowboard fans). It's worth posting the image that we have included to the right. You can clearly see that the surface low (white lines) has been captured by the upper level low (shaded contours) and pulled back to the northwest into Southeast Maine. 12 hours or one frame earlier on this run, the surface low was weak and southeast of Cape Cod. Again, a very powerful setup with potential for deepening surface low and some wintry precipitation to our north. We will have to carefully watch the progression of these features over the next several guidance suites, including the initialization and initial position of these features; currently we could be dealing with sparse data sources, attributing to the model flip flops.