Nice Wednesday, Increasing Clouds as Storm System Approaches Thursday

A tropical low is trying to organize itself in the Gulf of Mexico.  At the same time a trough is approaching from the Midwest and this will pick the system up and lift it along the east coast.  Heavy rain will lead to localized flooding and winds may gust close to 50 MPH at the coast.  Since this is the major weather during the short-medium, will focus on this today.

Observations/Short Term Forecast
As of 4 am temperatures were in the upper 40's in the higher elevations of MA, low 50's elsewhere

4 am 2 m temps (image weatherbell)

Here is the surface chart

WPC surface analysis 330 am

While high pressure along the VA coast is in control of our weather, the front along the US/Canadian border will allow for some mid level clouds to work into the region today.  The kicker is it will be warmer today than it was yesterday

06z NAM hires 2 m temps 4 PM (image weatherbell)

Tonight lows drop into the low to mid 50's.  Here is the surface chart tomorrow morning

WPC surface analysis 8 am Thursday

Currently the National Hurricane Center gives the low in the Gulf a 40% chance of development.  Again it doesn't really matter to us as a tropical connection is going to be established either way.  But here it is on infrared radar

GOES_East Rainbow IR image 545 am (NOAA)

Good convection which is the first clue that this system will produce a lot of precipitation.  It is also being sheared as the thunderstorms are all to the east of the center.  In a well developed tropical cyclone the heavy rain is west of the center, the high waves and high winds are on the east side.  Anyway the name will be Andrea and I'd say she becomes at least a depression today, possibly a storm.   Thursday high temperatures are in the low 70's

06z NAM hires 2 m temps Thur 2 PM (image weatherbell)

By Thursday evening the rain will begin to push into New England.  The surface chart

WPC surface forecast Thursday 8 PM

The simulated radar shows plenty of rain which is largely unrelated to the tropical disturbance 

06z NAM hires simulated radar Thur 8 pm (image weatherbell)

On Friday the low will be working into the Florida panhandle.  All precipitation Thursday evening/early Friday will be related to the surface front working towards the coast, driven at the 500 mb level by a trough diving east.  

WPC Friday morning surface forecast

But as Friday evolves and the tropical disturbance moves Northeast, an event called a Predecessor Rain Event is likely to break out somewhere in the Northeast.  The most likely spot is Upstate NY/Western New England.  We have a strengthening jet streak, a trough west of the tropical cyclone, and a ridge to the east.  There is also a low level boundary present (Cote, Bosart, Keyser 08).

00z CMC 250 mb jet Friday 8 pm (image weatherbell)

There should be a lull Friday morning in Southern New England.  However all in all 2-4 inches of rain will fall with isolated higher amounts.  The overnight models have consistently printed out less precipitation than the morning models.  The night shift at the WPC is less bullish than the day shift accordingly

WPC 5 day precipitation totals

My advice and what I will do is split the difference.  More on the winds and specific timing in the next post.  Have a good Wednesday.