Nice Weather until Wednesday, frontal passage and then onto the real fun

Model consensus agrees for the next 5 days that sunshine and seasonable temperatures will be the norm.  However around Tuesday/Wednesday a southern stream shortwave will move out of the GOM and up the Eastern US seaboard bringing heavy rain before a front moves through the region bringing below normal temperatures into the region.  Models disagree afterwards on the pattern for the weekend.  12z GFS shows a possible secondary low developing too far northeast of the region to bring significant precipitation to the region.  A few GFS ensemble members as of the 12z runs showed potential amplification of the northern jet stream with some signals of a +PNA developing quickly and exiting in the Nov 18-20th timeframe which is the time for the best chance of accumulating snowfall.  Best chances in New England remain in NE Maine coastline as a comma head develops and produces some good precipitation to the northwest of the surface low.  Again there is a good week before anything comes with better certainty.  Pattern resembles 50/50 low placement and -NAO Greenland ridging which will force at least a period of amplification, and the reflection of a +PNA ridging present in this period should allow better amplification of the polar jet shortwave trough.  If the models are right at this time as a consensus this system will just bring in the colder air stored over Ontario, Canada in this timeframe.  Again major amplification is difficult given the orientation and placement of the central US trough.  If this trough was closer to the OH Valley, then we would have a greater chance at snowfall.  However with the 850mb and surface circulations traveling to the north of the region, chances are the precipitation will be cutoff to the region so no substantial precip is likely.  Again this is still a low confidence forecast as the 00z EURO shows a large Great Lakes low, with the GFS family models showing a clipper moving through the Lakes and creating secondary cyclogenesis to the NE of New England.  Again big discrepencies in the forecast model family.

Next large precip threat comes with another frontal passage sometime in the 20-23 timeframe where a monster low will travel again through the Great Lakes states and the associated frontal boundary moves through New England as strong cold air advection pushes the frontal east and southeastward.  Lake Effect snows over the Great Lakes could become a problem over there for the Thanksgiving traveling period.  Strong cold air advection will bring high temperatures down to the low to mid 30s in this time frame, and the GFS is showing a fantasy range storm system sometime that Thanksgiving holiday weekend.  We need to watch the 26-28th timeframe as models are showing potential pattern change back to a +PNA/-NAO/-AO regime which should favor New England with a snowy and cold pattern heading into DEC.

Next update will be tomorrow, unless the 18z runs show something worthy of discussing.

12z model update:

As previously mentioned the 12z GFS operational and ensemble mean continued to remain the furthest northeast with secondary formation.  12z GGEM and EURO came in with a much further southwest positioned low, however are still at odds with the development with the secondary low.  Still a lot of questions and again, I will keep you ahead of the system.