Winter Storm Lexi Leaves Its Mark, More Snow?

(Note- I will begin to use the Weather Channel winter storm names.  The National Weather Service's official position is opposition to these names.  However they are growing in popularity and I find them useful.)
Winter Storm Lexi arrived yesterday and left its mark on Southern New England.  Tragically a 6 year old girl from Canton died when a tree limb fell on her while playing outside.  May you rest in peace Kaleigh Kenyon.  Tree limbs also fell on power lines and left nearly 180,000 customers without power at the height of the storm.  In eastern MA there are still about 50K customers without power.  In Rhode Island it looks like there are approximately 10-15K still in the dark.
MEMA power outages for MA
I don't have a snow total map yet but the highest total in MA was Worcester airport with 12.5".  In CT the big winner with 13" is Staffordville.  In Rhode Island Burrillville checked in with 12".  I am content with my snow map but I would have really nailed it if I made my 5-9" band a 8-12" band as a lot of places came in around 9. 10".  See the full list here for yourself.
NWS Boston seasonal snow round up post storm


So what is next?  First off today is pretty seasonable for February.  Temperatures in the mid to upper 30's with mostly sunny skies giving way to partly cloudy conditions this afternoon.   This will allow for some melting.  The temperatures drop back into the 20's tonight allowing for a refreeze.  Sunday is similar but a tad warmer and less clouds.  Now we turn to Monday.  Given this is a complex set up let me try and set the table.

First here is the upper air pattern this morning at 7 AM
12z NAM 500 mb vort 7 am (image NCEP)
First that jumps out is the complex in the southern plains ready to eject into the Southeastern states.  By tomorrow AM a storm system will develop in the Southwest Atlantic.
WPC surface forecast Sunday 7 AM
While we watch the Panthers pound the Broncos (but hopefully by less than 7) the upper air pattern will evolve to this.  One does not need to be a weather enthusiast to see the strength of this upper level low.  The low is closed and feeding off the gulf stream.
12z NAM 500 mb vort Sunday 7 PM (image NCEP)

This should continue right up the coast right?  Well not exactly.  The potential Tuesday system (more on that later) is moving out of the northern branch of the jet stream and could shunt this storm further east.  The overnight computer guidance largely favors that solution.  The problem is the stakes are high.  If the storm moves 50 miles north and west look what we get.
12z NAM 1000-500 mb thickness, qpf, mslp valid Monday 1 PM (image NCEP)
Temperatures inland will be much colder on Monday so at least we would not have to deal with the cement that fell yesterday.  But in turn snow ratios are higher and more snow falls.  For example here is Monday at the same time as the image above (1 PM Monday)
12z NAM Hires 2 m temps 1 PM Monday (image weatherbell)
Snow would likely start around or just after the AM commute Monday.  As of now Tuesday is complicated.  It depends on what storm number 1 does.  I feel that the threat from Monday is much greater than Tuesday.  So as of now here is my snow map.
Zack Green snowfall impact map Monday
I have to buy the potential of this.  So far this winter guidance has tended to bring storms further north and west as we got closer to the event.  Despite the long standing bias against the NAM it has done well this winter.  I may post tonight but if not I will have a Sunday AM update.  I'll try and figure out the mes of Tuesday today but as for now that appears to have much less potential than Monday.  The next winter storm name is Mars.  Less sexy than Lexi if you ask me.

Questions, comments, concerns, complaints on my facebook page or @zgreenwx on twitter.

-Zack Green

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