Monday, February 22, 2016

Winter Weather Advisory Posted for Light Snow Tuesday PM

 Update:
The winter weather advisory has expanded
Tuesday 1 PM NWS Boston advisories
The forecast below looks to be on track.  Snow begins around 5-6 PM in Massachusetts.  Probably a full school day for the teachers tomorrow.

Previous discussion below.

The National Weather Service in Taunton has posted a Winter Weather Advisory for Central and Western Massachusetts.  This may extend into Northern RI and CT as well as Middlesex and Essex counties in MA.  This runs from 4 PM Tuesday until Noon Wednesday. 
NWS Boston Advisories
This is for snow, sleet and freezing rain.  Snow breaks out from SW to NE around 5-6 PM.  It gets into Worcester and Boston closer to 7
18z NAM hires simulated radar 7 PM Wednesday (image Weatherbell)
It transitions to freezing rain after midnight.  As for snow totals- the NAM hires is probably a little high - but in general 1-3 inches across Central and Western MA
18z NAM hires accumulated snowfall 7 am Wed (image Weatherbell)
Next there will be some ice on top of this
NWS ice forecast
Yellow means icy spots expected while orange is widespread icing
Ice Storm Impacts
This may get teachers a delay on Wednesday but I won't guarantee that.  It's not something that would be called until the morning.  Next we move to heavy rain Wednesday night.  A nasty severe weather outbreak will occur in the South tomorrow as this low lifts north.  Here is the track
NWS WPC significant low tracks
Here is the project surface chart Thursday AM
WPC surface forecast Thursday AM
Here is the total precipitation through Thursday PM
WPC precipitation through Thursday 7 PM
With a strong low like that to our west we will see strong winds overnight Wednesday into Thursday.  Winds will be about as strong as they were last Tuesday.  That means some downed tree branches and isolated power outages.  I will update as needed tomorrow.  I suspect the winter weather advisories will be expanded.

-Zack Green

Sunday, February 14, 2016

Temps to Rebound After Arctic Blast Shatters Records

There is a new leader in the clubhouse for the top spot on my coveted "Top Weather Events of 2016" blog.   While there is not much competition so far it will take a significant event (Hurricane or Tornado) to knock this off.
2.14.2016 record low temperatures
Some fun facts via NWS Boston
  • Nantucket fell below 0 for the first time since January 16, 2004 (also -3)
  • Boston and Worcester each recorded lowest temperatures since 1957
  • Because Boston fell to -4 before midnight it also set a new record low for Feb 13.  After going 49 years with a record low in February Boston has now set one on back to back days 
  • Wind chills reached -44 in Worcester (see list)
    Recorded wind chills via NWS Boston
    Perhaps even more impressive is the fact that New York City broke a record that stood for 100 years 

NWS New York records
 Just an aside- we cannot deny that record highs have outpaced record lows across the United States for the last few 2 decades.  December was the warmest December on record by a lot.  But we also can't ignore that the last 3 winter have seen cold that rivals some of the all timers from previous era's.  Last February was the coldest month on record (100-140 years) for everyone except Boston where it was the 2nd coldest behind only Feb 1934.  If you support Bernie Sanders you need to ask yourself what would last night have been like if I didn't have natural gas or oil to heat my home?  I am 100% in favor of finding clean, sustainable energy but we have to actually look at what the weather is telling us.  We are seeing extremes on both ends of the temperature scale.  There is record warmth out west right now balancing the record cold in the east.  Even in a warming climate record cold arctic assaults can and will happen.

Temperatures will rise to around 10 today.  Tonight temps fall back below 0 tonight with the exception of Boston which should stay around 1 or 2.  The rest of the region is around -3 to -13 tonight with the coldest being in Western MA.  High temps tomorrow rebound into the mid 20's.  Some snow is likely tomorrow evening before it goes over to rain Tuesday AM.  How much and when?  It starts from South to North around 5-7 PM.  I think 1-3 is good for most of SNE
12z NAM hires accumulated snowfall through 4 AM Tuesday (image Weatehrbell)
Then we should see a transition to ice and rain.  Western MA, N CT and N Worcester County are at the highest risk for ice.  Winter Weather Advisories will likely go up later today for snow/ice.  That will make Tuesday AM slick.
WPC surface forecast 7 AM Tuesday
This storm is called an inland runner.  Basically it runs up the Appalachian Mountains to our west bringing with it strong winds heavy rain and warm temps.  For example by Tuesday at 7 PM temps are around 50 or just 65 degrees warmer than this morning!
12z NAM hires 2 m temps Tuesday 7 PM (image Weatherbell)
Overall a healthy slug of precipitation will fall.  If storm drains are clogged with snow and ice some street flooding is possible.
WPC 1-3 day precip
Finally the winds may be very strong as the lower jet stream will be ripping.  That said the upper air profiles currently warm the mid layers of the atmosphere enough to keep the damaging winds above our heads.  This will be something to watch over the next 24-36 hours. 

Stay warm today friends.

-Zack Green

Friday, February 12, 2016

Savage Albeit Short Lived Arctic Assault

While certainly not as exciting as a snowstorm the impending Arctic Assault is much more dangerous then any storm we have seen this winter.  The potential for harm to children and the elderly is much greater than even the snow storm last Friday that killed 2 people.  The good news is this will be a short battle with the cold.  Temperatures may be near 50 with whipping winds Tuesday afternoon.  A rare Wind Chill Warning is in effect from 4 PM Saturday to 12 PM Sunday for much of Southern New England.

NWS Boston hazards

Today is very cold but we can handle it. Temperatures do not begin to plummet until around noon tomorrow.  The surface map shows the Arctic boundary in the Northern Great Lakes/Southern Ontario
WPC surface analysis 7 AM
One can see the boundary on the surface temperature chart
RTMA 2 m temps 8 AM (image Weatherbell)
Today we stay in the upper teens with wind chills around 10.  Very cold no doubt.  When that boundary slides through tomorrow AM it will feel like a sucker punch to the jaw.  Here is the surface forecast (I've drawn in the boundary since the blue doesn't show up well with the snow squall threat)
WPC surface forecast 7 am Saturday
Notice that parts of Maine are going to get hammered with snow tomorrow.  A good 6-10"+ is likely for the Bangor to Eastport regions.  A few snow squalls are likely in Southern New England as haymaker lands. We could be looking at 2-4" down the Cape and Islands. Nantucket is already under a Winter Weather Advisory

The projected wind chills for noon tomorrow are already below zero into Worcester County.  So first lets take a quick NWS Boston weather class.  What is wind chill?
What is wind chill? NWS Boston
Now that you know what wind chill is let us look at the various wind chills expected through Sunday morning
06z NAM hires 2 m wind chill temps Sat 12 PM (image weatherbell)
Actual air temperatures start to go below zero around 4-5 PM in Western New England.  They go negative in Worcester around 6-7, and most of New England by 10 PM.  It could be approaching -10 by 10 in Worcester! 
06z NAM hires 2 m temps Saturday 10 PM (image Weatherbell)
Winds will be gusting 20-30 even at times up to 40 MPH.  So by 1 PM wind chills are are ridiculous -30 to -40.  Frostbite will occur within 10 minutes at these temperatures.
06z NAM hires 2 m wind chill temps 1 AM Sunday (image Weatherbell)
Now it is time for classroom part 2.  What are the signs of cold related illnesses?
Dangers of extreme cold NWS Boston
How can we prepare for this?
Cold tips - NWS Boston
Dressing for Cold - NWS Boston
Here are the records and my forecast.  Boston has not set a record cold minimum temperature in February since 1967.  That is amazing.  As cold as last year was it was a lot of cold high temps and temps a few degrees below zero which ended up giving most of the region its coldest month on record.  This is impressive stuff.
SOuthern New England record, forecast (via ME)
Stay safe friends this cold is no joke. 

-Zack Green

Tuesday, February 9, 2016

Snow Squalls in the AM

Good evening everyone.  We have some snow squalls on the way for tomorrow that will drop around an inch of snow for most people.  However in isolated areas up to 3-4" cannot be ruled out.  Lets review the last storm and talk about the squalls.

Here is the map of the yesterday's storm.  I was over by a few inches in most areas.  Totals were on the lower end of all scales.  At the end of the day the storm was 500 miles away and the locals factors failed to enhance the snow as much as I thought.  That said 4-10" from a storm 500 miles away is impressive.
NWS Boston snowfall map 2-8-16 event
3 years ago we were wrapping up one of the all time Southern New England blizzards.  The Blizzard of 2013 (or Nemo) was powerful and caused a lot of damage in SE MA due to coastal flooding and wind damage.
Blizzard of 2013 NESIS map
Just last year we also had a Category 1 snowstorm.  This one often gets forgotten but this was the storm that really began to bring the region to our knees.  The MBTA was dealt a death blow, areas roofs began to collapse and area roads began to be too small to accommodate 2 way traffic.  This storm ranks 7th on Boston's all time snowfall's with 23.8".
Blizzard #3 of 2015 NESIS
We aren't getting anything like that tomorrow but this just goes to show early to mid Feb is the "peak" of winter snow season in Southern New England.  So here is the radar tonight
Northeast Regional Radar Loop 728 PM
It is NOT impressive and it will not be.  But here is the National Weather Service Special Weather Statement
NWS Boston special weather statement
I do buy some action in Western MA and CT maybe to Worcester tomorrow AM.  Here is one high resolution model solution for tomorrow AM at the upper levels
23z HRRR 500 mb vort valid 8 am (image NCEP)
Here is the simulated radar
23z HRRR simulated radar 9 AM (image Weatherbell)
No delays, no closings, no early dismissals but just heads up driving to work in he AM.  Most people see less than an inch, if anything at all.  Some 1-2", even fewer 3-4".  I believe the Pioneer Valley and Northern Connecticut between 6-10 AM has the best chance to see higher amounts.  This may re-fire further east tomorrow afternoon but that is unlikely. 

-Zack Green

Sunday, February 7, 2016

Winter Storm Watches Posted for Southeast New England

3 PM Update 
The National Weather Service in Taunton has increased their snowfall forecast.  This is much more in line with my thoughts from this AM when I held back just a bit.
NWS Boston snowfall forecast 230 PM Sunday through Tuesday 7 AM
Now most of the area is under Winter Storm Warnings or Blizzard Warnings
NWS Watches, Warnings Sunday PM
I don't have much more to add.  Timing, impacts are below. Traveling tomorrow will be difficult, especially south of Boston. 

Previous discussion below

For the second year in a row a winter storm will threaten Southern New England the day after the Super Bowl.  The storm last year was more of a direct hit and I don't think many people cared after this (video via NFL YouTube channel, have to watch on YouTube).  They really should be playing today I hope I win some money today.
The storm last year dropped a widespread 12-18".
Post Super Bowl Storm 2015 via NESIS
I am not expecting a widespread 12-18.  That said if someone on the South Coast, Cape, or even Nantucket get a foot I would not be surprised.  As of now Winter Storm Watches are posted for much of SE New England with the exception of Southern Rhode Island.  They should be added today.  Also it is possible (probable?) the second blizzard warning of the season could be posted for the Cape and Islands later today.
NWS Boston Sunday AM advisories
I'll get into the start/end times, the winds, and some coastal concerns in a moment.  First lets look at what the storm is doing right now.  Here is the water vapor satellite image.  The storm is intensifying as it feeds off the warm gulf stream
NOAA GOES_East water vapor satellite
Here is the surface chart
WPC surface analysis 7 AM
At this point it appears the storm will track safely south and east of Southern New England.  That said check out the wind field in the storm
12z NAM hires 900 mb winds 6 am Monday (image Weatherbell)
 These winds are a few hundred feet up in the atmosphere.  So lets take a closer look at near surface winds 8 AM Momday
12z NAM hires 10 m winds 8 AM Monday (image weatherbell)
With these winds east and northeast facing beaches will be vulnerable for minor to moderate coastal flooding.  Here is a list of beaches/harbors that may see flooding tomorrow during the late AM/early PM high tide.  We must be thankful this storm is well offshore.  Here is the forecast surface chart tomorrow morning.
WPC surface forecast Monday 7 AM
So why would we get plowable snow with a storm so far offshore?  Well first of all remember the large wind field.  The storm is massive.  Second see the cold front south of New England?  As that front moves through overnight it will bring a fresh shot of Arctic air with it.  By 1 PM temperatures inland are in the low 20's.
12z NAM hires 2 m temps 1 PM Monday (image Weatherbell)
Ocean temperatures are running around 40-41.
OSTIA Sea Surface Temps (C) (Image Weatherbell)

Why does this matter? That is huge difference between air and ocean temperatures.  There is also a lot of energy with the storm.  As a result the snow shield is pushed well inland.  Now let's time it out.  Snow begins to fly at the South Coast around 4 AM.  It gets to the Mass Pike around 7 AM.    The snow makes it Western expansion between 7-10 AM and most of Southern New England (including Southern NH and coastal Maine) is snowing at varying intensities at noon.
12z NAM hires simulated radar 12 PM Monday (image Weatherbell)
Snow collapses in Western MA/CT mid afternoon and in Central MA/RI in the evening.  Snow lingers in E MA until 8-9 PM.  Snow ratios will vary big time from Central MA down to the South Coast.  Given temps a 15-1 or 20-1 ratio is likely in interior SE New England.  Given the warmer ocean 10-1 is a better bet across the Cape.  So what does that mean for totals?  There is some guidance that holds back on the precipitation so I am going to respect that.  That said I think I am selling this system short a bit.
Snowcast for Monday

Probably some higher amounts in Maine but that isn't really my focus so check out weather.gov for more info on northern areas.  Questions, comments, concerns please reach out. Enjoy the game tonight.

-Zack Green

Saturday, February 6, 2016

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

Rain Ending As Snow For The Blackstone Valley Tuesday

Tomorrow is Tuesday and surprise, surprise...precipitation is in the forecast.  WBZ went back and found that there has been measurable preci...