Significant Coastal Storm to Bring Rain, Gusty Winds, and...First Snows???

The potential exists for a rather significant coastal storm to impact southern New England heading into the end of the week. Much needed rainfall, gusty winds, and even some snow is possible. There are several pieces involved here and how they interact will determine the strength of the storm and the impacts we see. Let's dig into the science!

#1) Hurricane Zeta which is set to emerge into the southern Gulf of Mexico Tuesday morning. After making landfall late Wednesday in the vicinity of the Louisiana - Mississippi border, the remnants of Zeta  will rapidly progress through the Tennessee Valley, through the mid-Atlantic, and eventually pass just south of Long Island. 

#2) A closed area of low pressure across the southern Plains will eventually become an open wave as it pushes east through the Tennessee Valley. This system is a main player in the rapid speed of Zeta after it makes landfall. 

#3) A shortwave trough across southeast Canada amplifies (strengthens) as it approaches New England. 

#4) A strong area of surface high pressure slides into southeast Canada behind the shortwave trough. 

These features are all shown below using the 12z run of the  GFS from Monday looking ahead to Thursday evening:

The position of the high pressure and potential track of the low pressure (remnants of Zeta) are very critical as there will be quite a bit of cold air in Canada. In fact, 850mb temperature anomalies (temperatures about 5,000 feet off the ground) may be -10 to -20F below-average! 

The clockwise flow around the high pressure could support the transport of anomalously early season cold into portions of southern New England. Meanwhile, the counterclockwise flow around the low pressure could act to reinforce the transport of this low-level cold. 

In addition, an extremely strong jet streak will be placed north of the region with a jet streak in excess of 190 knots!!! The region will also be in a highly favorable quadrant of the jet stream which will favor vigorous upward motion and favor for low pressure strengthening off the coast. These factors also enhance the likelihood for much colder air to be drawn into the region. 

The verdict? Well, it's a bit too early for exact details and specifics, however, the signals and confidence continue to grow towards a significant coastal storm the day before Halloween. Potential impacts include; 

• Heavy rainfall (much needed!) 
• Strong and gusty winds 
• Potential for snow (especially for elevations above 1,000 feet)
• Accumulations are also possible above 1,000 feet. 
• Snow can't even be ruled out across elevations lower than 1,000 feet though the likelihood decreases quite a bit as you near the immediate coastline. 

Bottom line, this needs to be watched as many could see their first flakes of the season; including the potential for accumulating snowfall (with the highest likelihood above 1,000 feet). One final thing to mention...we are heading towards a full moon so costal flooding due to higher than usual high tides is a possibility.