Winter Storm Stella- Timing, Impact, Totals

Good afternoon everyone.  Stella is on her way and she is poised to be a disruptive winter storm.  Snow flies before dawn and sticks right as the morning commute begins to get heavy if anyone is actually on the road tomorrow.  Snow will rapidly accumulate beginning mid to late morning.  Winds will gust over 35 MPH beginning around 10 AM and they will increase to 45-60 MPH Tuesday afternoon.  Coastal MA/RI/CT will likely see winds approach 65-70 MPH.  Snow rates will increase to 2-4"/hr between 11 AM and 5 PM for much of Western, Central, and Northeastern Massachusetts.  Northern RI will also see incredibly intense snowfall rates.  Snow lessens Tuesday evening and we are left with isolated snow showers on Wednesday.
If only we could all have this much fun in the snow
Most of the "Hall of Fame" level New England snowstorms are long duration, 15 round Ali-Frazier level boxing matches.  This storm is much more like Amanda Nunes beating the hell out of Rhonda Rousey in 48 seconds.  It may be brief, but we are going to know Stella was here.

NWS Headlines
The National Weather Service has posted a *Blizzard Warning* for much of Massachusetts, Northern RI, and most of CT.
NWS PM Headlines
A *Winter Storm Warning* is posted for Southern RI and SE MA (including Boston).  A *Winter Weather Advisory* and a *High Wind Warning* exist for the Cape and Islands.

General Overview
Stella is about to re-develop near the North Carolina coast.  Surface pressures have been falling near the Appalachians as the parent vortex begins to transfer its energy to the ocean side of the mountains.
NWS/NOAA/NCEP Rainbow IR satellite 245 PM
At the surface, low pressure in the Gulf is adding moisture to the system.  Meanwhile, strong high pressure is the dominant weather feature in Southern Canada/Northern US.

WPC Surface Analysis Monday 2 PM
The true impact of the high is to produce temperatures cold enough for snow.  Here is a look at the minimum temperature forecast tonight across the lower 48.  These are 5-10 below average for this time of year in the northeast.  That high will also help strengthen the low-level jet stream tomorrow, which will lead to the damaging wind potential.
NWS National Minimum Temperature Forecast Tuesday
.   The presence of energy in the Gulf of Mexico will arm Stella with plenty of moisture as she makes her way up the coast tomorrow.  Warm moist air will flow over the cold air entrenched in the Northeast.  This is a very efficient snow making process.  Another efficient precipitation process will be the presence of a very tight temperature gradient near the coast.  For example, it might be 44 in Hyannis and 26 in Worcester.  The low will also undergo "bombogenesis" as it moves up the coast (greater than 24 mb drop in 24 hours).

Storm Timing/Impacts
The first snowflakes will arrive in MA from SW to NE between 5 and 8 AM.  Here is how the low will evolve at the surface starting at 2 AM tonight, going in 6-hour increments.
WPC Surface Fronts/Precipitation Tuesday 2 AM, 8 AM, 2 PM, 8 PM
Temperatures will be in the mid to upper 20's for those north of the pike and outside 495.  Temperatures will warm to near 32 in Southern Worcester County and around the Pike in Eastern MA.  It will be warmer in SE MA.
NWS Max temperatures Tuesday (image Weatherbell)

Snow rates will be 0.5-1"/hr between 6-9 AM.  Between 9 AM-3 PM, Stella really begins to crank out snow.  At 9 AM there will be 2-4" (at least) of snow on the ground across the region.   Here is the future radar for noon time tomorrow.
12z NAM hires 3km sim radar Tuesday 12 PM (image Weatherbell)
Visibilities will drop to under a quarter mile by 9 AM, but when this band comes through they will be 0.1 of a mile or less.
12z NAM hires 3km visibility forecast Tuesday 12 PM (image Weatherbell)
At the same times, winds will be peaking around 50-55 MPH across much of the interior.  At the coast winds near 60-65 MPH and on Nantucket winds may gust to near 75!
12z NAM hires 3km surface wind gusts, mph Tuesday 12 PM (image Weatherbell)

The heaviest snow continues until around 3 PM-5PM when some sleet may mix in all the way to 495 and the Mass Pike as the low crosses Cape Cod.  The sleet may also mix in briefly in the Blackstone Valley.  Still, we will finish with another 1-3" as temperatures crash when the low moves into the Gulf of Maine.  Stella will feature a very strong band of winds a few thousand feet up in the atmosphere.  When the low crosses SNE this wind will be out of the east which will warm a few layers of the atmosphere.  That will be enough to turn parts of SE MA over to plain rain, albeit with very strong wind gusts.  

Precipitation ends in Southern New England by 8 PM.  Temperatures drop into the teens by Wednesday AM.  So first, here is how much precipitation is expected to fall.
NWS/WPC precipitation forecast through Wednesday 8 PM (image Weatherbell)
Out of all of that, here is how much snow the NWS expects.
NWS Total Snowfall forecast through Wednesday 8 PM (image Weatherbell)
That is probably a bit high in Southeastern Worcester County as the sleet will make that more like 14-15".  That said if it stays all snow then yes, expect 14-20".  This forecast would make this a top 5 March snowstorm for Boston, Worcester, Providence, and Hartford and certainly a 1-day record.

There are also coastal flood threats throughout the Northeast.  There was a full moon yesterday so tides are still running high.  A 2-3' storm surge will accompany Stella so minor to moderate coastal flooding is likely in the usually prone areas (Hull, Scituate, Brant Rock etc).  See the National Weather Service for more on this hazard.

I plan on starting a live blog tomorrow, so follow along here and post questions, comments, and photos to ZG Weather.  That will be fun as long as the power is on!!  There are a ton of hazards with this storm so please stay off the roads tomorrow and be ready for power outages.

-Zack Green


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