A cold front will work into northern New England today, with thunderstorms cropping up ahead of it. This front will slow down as it makes its way through New England thanks to an area of high pressure just offshore of the region. This slowing of the front will cause the line of storms to decay as it pushes southward. The highest chance for storms will be across the Champlain Valley, Great North Woods and northern Maine.
There is a small risk for severe thunderstorms to develop. The arrival time of the front has been trending earlier, with storms arriving in Vermont in the early afternoon. This earlier arrival time may limit severe weather as the storms would arrive before maximum afternoon heating and instability. Still, northern Vermont may still see some isolated severe storms.
Northern Maine looks to see more numerous storms later in the afternoon. Like Vermont, northern Maine (and the Great North Woods of New Hampshire) has a chance for isolated severe storms to develop. While the storms are looking to fire later in the afternoon in these areas, conditions are not favorable for a widespread severe outbreak.
HRRR showing more numerous thunderstorms across northern Maine later this afternoon:
Storms will become more scattered and eventually isolated moving south of the regions mentioned above. The further south and east you are in New England, the less likely you are of seeing a thunderstorm, although some light, spotty showers will be possible later in the evening through the overnight as the front moves through.
The greatest threat from these thunderstorms (both severe and non-severe) will be flash flooding. Rainfall rates in excess of 1 inch an hour are likely with the storms, and the storms will be slow moving as the front itself begins to slow down. With the potential for multiple rounds of storms to move through northern areas, storm training (when multiple storms move over the same area) is a concern. Flood watches are in effect from noon through 10 pm for northern Vermont.
On the 4th of July, storm training led to a major flash flooding event across Connecticut and Rhode Island, including the Hartford and Providence Metro areas. While the set up was different in that case, something similar could occur in northern areas if training does develop.
Into this weekend, the front will stall across New England, allowing a wave of low pressure to ride along it. This will set up another round of potentially heavy downpours for Sunday through Tuesday. Saturday has been trending drier, but scattered showers could pop across the region.
The further west you go in New England, the higher the chance is for rain, storms and flooding downpours on Sunday, although showers will be possible across New England Sunday afternoon, the showers will be less frequent the further east you go.
Euro model showing heaviest rain in western areas Sunday evening, this continues to slowly eastward for Monday:
This system will very slowly push eastward from Sunday night through Tuesday. As the system moves east, the threat of heavy downpours and storms will also shift east, although the greatest threat of flash flooding will likely be diminished, but not completely gone. We'll need to keep watching the timing of all of this tomorrow, so stay tuned for forecast changes as the threat of flooding in eastern areas could increase.
Early indications are showing the front clearing by the middle of next week, allowing drier weather (dri-ER needs to be emphasized as in this overall unsettled pattern, there is never a zero percent chance of rain). There are also indications of temperatures increasing mid next week.
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