Another Deluge On the Way

Today most certainly felt more like fall than late July. In fact, Boston's high temperature of 67 corresponds with the average high we see on October 1st! Cool air will be the least of our problems however, as a stalled off shore frontal boundary will allow a developing low pressure to push up the east coast and drench us tonight and through most of tomorrow.

A developing low pressure, currently situated off the coast of North Carolina will ride the stalled front due north, tapping into some tropical energy being provided by a cluster of thunderstorms further out in the Atlantic.

This topical energy will create a very heavy rain sheild that will rotate back into the area starting tonight. Latest models show some really heavy rain falling, especially along the south shore and coastal areas.

With the rain totals like this and the tropical downpour narture of the precipitation, the NWS has issued a Flash Flood Watch for much of eastern MA starting tonight and lasting through tomorrow afternoon.

Take a look at one models loop of the expected rainfall through 2AM. Definetly a washout!
Loop of Friday rain

Bottom line, tonight and tomorrow are not good days for outdoor activities. The sox will be lucky to finish their game tonight. Heavy rain won't start until 10/11 tonight and thankfully we should see some drier weather (but still cloudy) by late tomorrow afternoon.

Tuesday Soaker. Severe Weather This Afternoon?

Boston is currently under a Flash Flood Warning until 3PM this afternoon. A warm front sitting right over Massachusetts is providing the prefect breeding ground for heavy downpours to develop and drop torrential rains over the area.

Dew points are very high (mid 70's) and the precipitable water values (how much moisture is in the air) are also extremely high. All signs point to a lot of rain falling over the next few hours in eastern MA. We just had 1.30 inches of rain in 15 min here in West Roxbury. Totals like that will cause street flooding fast which is the reason for the Flash Flood Warning.

For now, heavy rain is our problem. As we move towards the afternoon, severe weather may be in the works for parts of the region. The atmosphere remains very unstable and with a warm front providing the perfect boundary for development, expect to see more storms later this afternoon. Daytime heating (albeit limited today) will provide an extra boost for these storms, increasing the possibility of damaging straight line winds and even some rotation.

Short range models show a strong line of storms developing by 4/5 this afternoon.

 

The SPC has also put us under an increased chance for rotating storms and weak tornado development. I doubt we see any tornadoes, but with such a juicy atmosphere and a low ceiling height, I do believe we may see a tornado watch or even warning issued at some point this afternoon. 

I will keep you posted!

2:30 PM Update: Storms Starting to Develop Ahead of Cold Front

Day 7 of the heat wave will be the last day, as a strong frontal boundary is slowly marching south east, bringing with it some much needed relief from the heat and humidity.

Clear skies have lead to decent daytime heating once again, with surface temperatures over 90 degrees across all of SNE. Dew points remain quite high as well, in the low 70's for most. This has lead to a quickly destabilizing low level atmosphere, which will promote favorable conditions for thunderstorm growth towards late afternoon.

The current radar over SNE shows these storms starting to pop along a secondary frontal boundary draped from Cape Ann back west through Worcester county as noted below in the red circle.

As the main cold front continues to push to the south, storms will continue to develop along this secondary boundary, especially in areas along and to the south of the Mass pike. As shown below, these areas have the steepest low level lapse rates, which makes these locations the most favorable for storm growth.

The storms this afternoon will feature heavy rain, thunder, lightening with the outside chance of small hail and damaging straight line winds. As they approach the coast, they will begin to become somewhat scattered in nature, as opposed to the organized line form they are currently in.

I will update as the afternoon goes on. In the Boston area, expect some wet weather sometime after 5, with much of the action clearing the metro area by 8.