A warm front is currently pushing northward across Western and Central Mass and as of midday is located very near the Mass Pike. It is expected that heavy showers and thunderstorms will move along this front later this afternoon and this evening and pose a risk for flash flooding and severe weather. Flash Flood Threat: It appears that the main threat with the heavy showers and thunderstorms will be extremely heavy rainfall. The potential is there for thunderstorms to drop 2 to 3 inches of rainfall in a very short period of time as they move through. In addition, there is also the possibility for training of thunderstorms where multiple thunderstorms move over the same location for several hours & this could exacerbate the flash flood threat. The current timeline for thunderstorm development will be that they will begin to affect the entire area between 3 and 5 pm this afternoon with widespread heavy showers and thunderstorms affecting all of Western and Central Mass through the first half of tonight. The shower and thunderstorm activity should gradually diminish after midnight tonight. Rainfall amounts later this afternoon through tonight will range from 2 to 3 inches with local amounts of 4 to 5 inches possible. Please be aware that where the ground is extremely wet right now that this additional rainfall is likely to lead to rapid flooding of urban areas and streams and small rivers. We may also have to keep an eye on the bigger rivers (Connecticut and Blackstone Rivers) for the possibility of significant rises. Severe Thunderstorm Threat: The atmosphere has become very unstable, especially across areas along and south of the Mass Pike. Because of this the thunderstorms that do develop late this afternoon and the first half of tonight will be strong to severe. Any strong to severe thunderstorms will be capable of producing wind gusts of up to 50 to 60 mph. Another possible threat, albeit a very low one, is the possibility for a tornado or two with any thunderstorms that can attach themselves to the warm front, which will remain in place near the Mass Pike. That warm front will be a source of heightened low-level wind shear and spin for thunderstorms to take advantage of. It is expected that strong to severe thunderstorms will develop across all of Western and Central Mass between about 3 pm and 5 pm this afternoon and continue through the first half of tonight. The severe thunderstorm threat is expected to end between about midnight and 2 am tonight.
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