Rain Thursday- Totals, Timing and a Pattern Change

Low pressure will again track to our west on Thursday, delivering heavy rain and strong winds to Southern New England.  The National Weather Service (NWS) has issued a *Flood Watch* for the entire region.
NWS Boston PM Headlines 
Some rivers are near, or at flood stage already.  The NWS has issued a *Flood Warning* for these.  There are only 2 in Massachusetts at the moment but that will change tomorrow.

The Blackstone isn't forecast to reach the "Action" stage of 8 ft, but I wouldn't be surprised if it does.  I haven't seen it as high as it is right now in years.  Here are the current conditions and the forecast simulation over the next 48 hours.
NWS river forecast Blackstone at Northbridge
To find your local river (not all are monitored, just the ones that most often misbehave and impact lives and property) please use this link.

General Overview
A big time severe weather event is taking place in the Southeast as our storm tracks into the Ohio Valley.    There are almost 77 million people under the threat of severe storms today (76, 628,664 to be exact).  The light green shade is not included in the threatened population.
SPC Day 1 Severe Weather Outlook 
  Here is the surface analysis as of 2 PM.
WPC Surface Analysis Wednesday 2 PM
Warm moist air is feeding thunderstorms across the South.  Some storms have already produced tornadoes but it seems the worst is still to come.  The system is loaded with moisture as it is drawing energy from the Gulf of Mexico.
NWS/NOAA/NCEP GOES_East Water Vapor Satellite 
The severe weather is one thing and the radar is showing supercell thunderstorms develop in Alabama as I type.  The heavy rain is another.  Atlanta, GA has already received over 3" of rain and more is likely as the trailing cold front clears the Peach State.  We don't have to worry about tornadoes in SNE, but that rain is heading our way.
NWS Southeast Regional Radar Loop

Storm Impacts, Timing
By 2 AM the low will be tracking through Indiana and Ohio.  It will not yet be raining in Southern New England but expect some fog.
WPC Surface Fronts/Precipitation Thursday 2 AM
The precipitation begins in Southwest CT around 530 AM.  It will reach Worcester between 7-8 AM and Boston by 9 AM.
19z HRRR Simulated Radar Thursday 9 AM (image Weatherbell)
The first surge of rain will occur as a moisture moves north with a warm front.  There may be a brief lull in precipitation in the early PM but as the surface low moves across SNE, a second heavy batch of rain will fall.  With this second batch, strong winds and thunder and lightning are possible.  The second wave looks to peak around the same time as the evening commute.
18z NAM hires Simulated Radar Thursday 6 PM (image Weatherbell)
Steady rain will through early evening before tapering to showers.  Everything is gone by Friday AM.   Total rain is 0.75-1.5" with higher amounts possible in Western Southern New England.
NWS Precipitation Forecast Through Friday 8 PM (image Weatherbell)
 Winds will gust 40-50 MPH in SE MA and 20-35 MPH elsewhere across the region.  Temperatures will not get out of the mid 40's in Central and Eastern MA, but a surge of 50+ degree temperatures will move into SE and Coastal New England.
NWS Max Temperatures Thursday (image Weatherbell)
Temperatures will stay below average on Friday and Saturday.  Friday will be mostly cloudy with a slight chance of a shower.  Max temperatures will be in the upper 40's.  On Saturday it will be brighter and a little warmer.  Most will be in the low 50's, although the higher elevations may max out in the upper 40's.  

I don't generally forecast past 4-5 days for free, but it has been a rough stretch of weather around here.  Therefore...
ECMWF 10 day Hi/Low Temps (image Weatherbell)
Talk to you tomorrow.

-Zack Green

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