Monday, November 19, 2018

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 precipitation on 9 of the last 11 Tuesdays.

For many north and west of 495, tomorrows precipitation comes in the form of snow.  While all rain is on the table in Rhode Island and Southeast Massachusetts, Southern Worcester County, Southeast Middlesex County, and Essex County will deal with mostly rain but there will be mixing at times before ending as a coating to 1-2" of snow.  We clear out Wednesday before historic cold invades for Thanksgiving.

A Winter Weather Advisory has been issued for Northern Worcester County, parts of Western MA, Southern VT, Southern NH, and Southern ME. 

NWS Monday PM Headlines
I would add Northwest Middlesex County to this and I would also add Northern Essex County to this and they may be added this evening or tomorrow AM.   There are no headlines for the Blackstone Valley and I don't anticipate any being issued, although untreated roads will get slippery tomorrow afternoon.

General Overview
Another wave of low pressure will track along the Southern New England coast, increasing in strength as it does so.  Snow begins to fly near the MA/NH/VT boarder just after midnight.  A few showers will be possible in the Blackstone Valley at this time but most of the precipitation holds off until 5-6 AM.  Even in the Valley, some precipitation may fall as sleet or freezing rain but the predominant p-type will be rain.    I will urge caution when traveling. 

WPC Surface Fronts/Precip Tuesday 7 AM. 1 PM, 7 PM

Temperatures will be in the low to mid 30's and will fall a bit during the day.  So as we get to the afternoon, the snow that will be falling north and west of  495/Pike will sag south and east.  This change happens in the Blackstone Valley late Tuesday AM. 

18z HRRR Simulated Radar Monday 8 PM to Tuesday 9 PM (image
Tuesday night we start to head towards Mid-Winter type temperatures as an Arctic air mass invites itself over for Thanksgiving dinner.  More on this tomorrow.

Timing and Impacts
From the Pike to Rt 2, I expect 2-4" of snow, including the city of Worcester.  3-6" amounts are likely in extreme Northern MA and into Southern VT, NH, and ME.  I also expect 2-4" around Lawrence, Haverhill, and Methuen.   Snow could briefly fall at rates of 1"/hr in these spots late morning and early afternoon.  I am only expecting a coating to 2" around and just south of the Pike.  This image is from the HRRR model and I think it is spot on.  (Note- Click to enlarge all photos.)

18z HRRR 36-hour Snowfall (image
It always amazes me how many people in New England have vehicles that do not perform well in the snow.  Its also early in the season so not everyone has their snow tires yet.  As a result, that coating to an inch in the Blackstone Valley can very easily screw up traffic.  The take home message is to give yourself some extra time for both commutes tomorrow.  It looks like it is going to be a long winter.

-Zack Green

Wednesday, November 14, 2018

Winter Storm Headlines Issued Ahead of Thursday-Friday Storm

The National Weather Service in Norton, MA has issued a *Winter Storm Watch* for interior Southern New England a *Winter Weather Advisory* for communities inside 495 and RI/S CT.

NWS Boston Headlines (CLICK TO ENLARGE)
The watch begins at 7 PM tomorrow evening and continues until 7 AM on Friday.  There is little doubt that precipitation begins as snow.  The snow will change to sleet and freezing rain and eventually plain rain.  The exact timing of this transition is still a bit of a wild card.  Many communities will also end as snow Friday morning/early Friday afternoon as the storm races into the Gulf of Maine.  The highest uncertainty is from Hartford to Worcester to Lowell where 6+" of snow is possible if it stays all snow.  Let's discuss.

General Overview
WPC Surface Fronts/Precipitation Thur 7 AM, 7 PM Fri 7 AM, 7 PM
The storm system will lift northeast tomorrow, spreading snow, sleet, freezing rain, and rain up the Eastern Seaboard.  Working in favor of snow is the cold air mass already in place across the Northeast.  Temperatures tomorrow will be in the upper 20's/low 30's.  By 7 PM temperatures will be back in the upper 20's.  That sets the stage for frozen precipitation to begin as the storm begins to reform near the Mid-Atlantic coast. 

18z NAM 3km Sim Radar/P-Type Thurs 7 PM (image Tropical Tidbits)

The majority of the snow falls during the 7 PM-midnight time frame.  Solutions diverge as the clock turns to Friday.  The EURO model makes this a Cinderella snow and keeps the fun going past midnight.  The American NAM turns it into Sleet-fest 2018.   The NAM has trended a bit colder in its latest run.  Working in the NAM's favor is the calendar.  The "warm" sea surface temperatures mean any wind from the east will end the snow and cause a change over to sleet and then plain rain.  A storm track along Long Island and over the Cape would also favor a change over to sleet and then rain or drizzle.

This is the EURO at 11 PM tomorrow night.

12z EURO P-Type/Mean Sea Level Pressure Thurs 11 PM (image
The NAM at the same time.
18z NAM 3km P-Type (image

What is causing these differences?  Subtle differences in the temperature profile, which is not uncommon at this time range.  The calendar and the track of the low certainly favors a change to sleet and rain.  Despite that, the temperature profile does support heavy snow especially with heavy precipitation.  So where does that leave us?

If you are traveling home from Hartford or Providence, leave a bit early as the beginning of the snow will fall at the end of the evening rush.  The commute from Boston and Worcester should be fine.

The initial burst of snow will drop 2-4" of snow, with rates near 1"/hr between 9 PM-12 AM.  As the upper levels warm, snow changes to sleet and then freezing rain or drizzle.  It will be tough to dislodge the cold so this will likely continue until sunrise.  This happens first in RI and Eastern Massachusetts, especially inside 95/128.  Then it will work towards 495, the Pike, and Rt 2.  An extra hour or two of snow means an extra inch or two of snow.    As the precipitation intensity decreases, the snow/sleet will turn to drizzle or freezing drizzle.  This really is a mess!  

Allow of extra time Friday morning because the commute will be slow, especially those coming from Central and Northeast MA.    For school administrators and public works departments, my advice is to plan for 4-7" of snow as well as 2-3" of snow followed by sleet and freezing rain.  Here are the NWS totals for both snow and ice.

NWS Snow/Ice Forecast (CLICK TO ENLARGE)
As the storm departs late Friday morning/early Friday afternoon expect one final round of rain south of the Pike and snow north of it.  Winds increase behind the storm and cold air returns for the weekend.    I will be at a conference tomorrow but I will get an update on the blog one way or another.

-Zack Green

Tuesday, November 13, 2018

Stormy Pattern Continues, First Snow Likely For Many Thursday Night

When I look into your eyes

I can see a love restrained
But darlin' when I hold you
Don't you know I feel the same
Nothin' lasts forever

And we both know hearts can change
And it's hard to hold a candle
In the cold November rain

(If you now have Guns N' Roses in your head and have 10 minutes to kill, you can find the music video for November Rain here.)

Rain has been a constant theme so far this fall, continuing a pattern that declared itself in July.  Since July, Worcester is averaging 5.7" of precipitation per month!  That does not include the 4.94" that has fallen so far in November, which doesn't include today.  We have a 6" precipitation surplus over the past 5 months and that will only grow as November progresses.  Flooding has not yet been a major issue.  So far, the spacing between these rain events has been long enough to allow for the rivers to breathe.  Even with today's event, most predictions keep the Blackstone River in its banks over the next 7 days.  You can check on your local rivers here.

WSI Intellicast Northeast Regional Radar 930 AM

This storm system is helping to kick off what will be a banner week for Thanksgiving skiing in Northern New England.  The rain will end early this afternoon in Southern New England with clearing skies and a sharp temperature drop this evening.   Temperatures tonight will fall into the teens in NH, VT, and ME and into the mid 20's across MA, CT, and RI.   Max temperatures tomorrow will struggle to get into the mid 30's in Central and Western MA.  Temps will be in the upper 30's across CT, RI, and Eastern MA.

NDFD 2 m max temperatures Wednesday (image
Temperatures Wednesday night into Thursday morning will be in teens most places.  Even across the Cape and Islands temps should be in the mid 20's.

NDFD 2 m min temps Thursday AM (image
High pressure will be in control so mostly sunny skies will accompany the winter blast on Wednesday.  The high will begin to be pushed to the east by a developing storm system in the Southeast US.  By Thursday AM, a sprawling, messy system with lots of moisture will begin moving northeast.  High clouds will also arrive prior to the precipitation.  Thursday afternoon will feel and look a lot like winter.

WPC Surface Fronts and Precipitation Thursday 7 AM
 The Thursday evening commute should be just fine in Southern New England, although I will be watching the trends.   Temperatures Thursday will struggle to get out of the low 30's and will be dropping into the mid to upper 20's by Thursday evening.   The cold, dense air mass will tough to dislodge initially so everyone in Southern New England begins as snow.

12z NAM WRF Hi-Res Simulated Precipitation Type Thursday 7 PM (image

Some snow will change over to sleet and freezing rain as the storm tracks near Long Island and across the Cape and Islands.  The snow will quickly turn to plain rain across Eastern MA and Southern RI just after midnight.  Snow will hold on a bit longer in Worcester County before turning over to rain before 5 AM south of the Pike.  Snow turns to sleet, freezing rain, and then plain rain around 7 AM south of Route 2.  I'll have to watch the Merrimack Valley in case cold air holds on longer than currently modeled, as history tells us it may.   Rain will continue through the early afternoon, maybe ending as some snow/sleet/freezing rain before tapering off.

The Bottom Line

Snow begins after 7 PM on Thursday.  Accumulating snow falls from around midnight to 4 AM in Southern Worcester County.  Accumulations of 1-3" are likely.  A brief burst of sleet and freezing rain is possible between 4-6 AM before going over to all rain.  Although annoying, with a little bit of extra time everyone should be able to get where they need to go.  Consider this our "fall training" for winter.

-I will update tomorrow with the latest trends and timing and the all important snow accumulation map.

-Zack Green

Biggest Snow Storm Of The Season Heads To Impact Region Tonight

The National Weather Service (NWS) in Norton, MA has issued a * Winter Storm Warning * from 7 PM tonight until 10 AM Wednesday.  A widesprea...