Tracking Winter Weather Threats Over Next Few Days

Winter Storm Niko delivered yesterday and helped wipe out the seasonal snow deficit in all of the four major climate sites.  The storm will be remembered for the heavy snow band that dropped 2-4"/hr yesterday afternoon and for all of the lightning and thunder that it produced.  Thundersnow occurs when ice/snow crystal are carried high into the atmosphere by strong vertical motion (or updrafts).  When the charge separation becomes too great the atmosphere returns to equilibrium by a lightning strike.  Yesterday's storm had a lot going on physically that enabled over 100 strikes.  I didn't see/hear any yesterday but I do remember my first thundersnow experience.
Jim Cantore Thundersnow Worcester, MA  12-7-1996
Here is the radar loop from yesterday.  It took awhile to get going in parts of Eastern MA but once the storm got cranking so did the snow.
Intellicast 24 hour radar loop Thursday 2/9/2017
I rate this one as a major, memorable storm.  It's not in the top 10 for me but I will remember all the lightning I saw on radar and the intense snow band yesterday afternoon.  Several schools had their first snow day yesterday.  I don't believe it will be the last.
NWS Boston 2/9/2017 totals, year to date, average to date via NWS NOWdata daily almanac 
Short Term Forecast
Yesterday's storm is off in Atlantic Canada. Winds will increase this afternoon as cold air is re-enforced across the region.   At the same time, a warm front is steadily advancing NE.   The two air masses will clash and snow will fly again overnight into Saturday AM.   Temperatures this afternoon max out in the low to mid 20's before dropping back down into the teens overnight.   The warm front will be driven by an upper-level ridge that will is moving to the east.
NOAA/NWS/NCEP GOES Composite US water vapor satellite 1215 PM Friday
The low pressure that will responsible for tonight/tomorrow AM snow is currently in Manitoba, Canada.  This clipper (or Manitoba Mauler) will combine with the air mass clash from the warm front/cold air to drop a few inches of snow.  This will be minor but I think it's enough to get the plows/sanders out. Here is the forecast surface chart at 1 AM tonight.
WPC Surface Fronts/Precipitation Saturday 1 AM (image Weatherbell)
Snow begins around 10 PM tonight.  It will not really begin to accumulate until 1 AM.  Maybe 1-2" by 5 AM will be on the ground.  Another 1-2" is likely Saturday AM before temperatures climb into the 30's and we a get a brief break from the snow.  The last snow will move offshore by 11 AM.
16z HRRR Sim Radar Saturday 5 AM (image Weatherbell)
Temperatures climb into the low 40's in CT, RI, and SE MA tomorrow afternoon.  Temps will be in the upper 30's in C MA and NE MA.
NWS Boston Max Temps Saturday (image Weatherbell)
Saturday Night and Beyond
The atmosphere is primed for snow and the weather pattern is set to deliver.
WPC Surface Fronts/Precipitation Sunday 7 AM
The Sunday AM weather map does not look all that spectacular.  The original low will not explode until it gets into the Atlantic Ocean.  Still, precipitation is set to begin before noon time on Sunday.  It may begin as some sleet and rain before going over to a heavy wet snow Sunday afternoon.  Parts of SE MA will be mostly rain on Sunday.  Bristol, Plymouth, Barnstable, Kent, Newport, Washington, Dukes, and Nantucket counties will likely see rain for awhile Sunday afternoon.  Everyone goes to snow overnight Sunday into Monday.
WPC Surface Fronts Monday 2-13-17 7 AM
How much snow falls during the day Monday depends on where the low stalls in the Gulf of Maine.  If it is close like the WPC believes more snow falls for a longer period of time Monday.  If the low is further out to sea snow ends after 7-9 AM Monday.  This is what I will be watching for as I go over the data this weekend.   Another problem will be the winds.  This storm will get strong, quickly, Sunday night.  Blizzard warnings will be needed for parts of the area.

This next storm will be more difficult to forecast because there is a lot going on.  As of now (1 PM Friday) I expect snow to begin before noon in Worcester County and points north/west.  It really cranks between Sunday 1 AM and Monday 1 AM.  I expect areas that stay all snow to have double digit snow totals.  Temperatures will also drop for the second half of the storm as the low moves into the Gulf of Maine.

I will update tomorrow.

-Zack Green


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