Scattered Thunderstorms on Tap for Saturday in New England

The weekend will be heavily influenced by a frontal system passing through the region. This system will try to lift its warm front into the region during the day Saturday. This will place at least southern New England within the system's warm sector. A triple-point low (which is an area of low pressure that forms where a cold, warm and occluded front meet) will likely cross New England, paving the way for thunderstorm development.

There may be two main rounds of storms, one in the morning as the warm front lifts northeast and one in the late afternoon and evening within the system's warm sector ahead of the cold front. Recent guidance has backed off somewhat on the morning round of storms. Still, some pop-up showers and storms remain likely in a few places late this morning and early this afternoon.

Below: FV3 showing potential weather late this morning:

As this activity moves eastward, coverage of storms will gradually increase with the second and main round of storms later in the afternoon and into the evening. Once the area is within the warm sector and daytime heating and instability rises, storms will likely gradually increase in coverage through the afternoon, occurring from west to east. Storms will begin to push eastward and weaken through this evening.

Below: FV3 showing potential weather later this afternoon:

With a warm front and triple-point low crossing New England, there will be the possibility of some strong to severe storms. Looking at the main ingredients for severe storms, the approaching front and triple-point low will provide the lift needed for storms. Continued humidity will be in place for storms to feed on as well.

Instability is a major question mark as it will hinge on how much breaks in the clouds can be achieved. CAPE values may build to around 1,500+ joules/kilogram, with higher values in western New England. This is enough to signal an unstable atmosphere and one that is favorable for strong storms. The article linked in the above paragraph explains CAPE values and what it means.

Below: HRRR showing projected CAPE values this afternoon:

If clouds from this morning remain stubborn, it will greatly limit what can develop in the afternoon. On the other hand, plenty of breaks in the clouds will pave the way for more numerous afternoon activity. Recent guidance and recent weather suggests skies will be able to at least partially clear for a time, especially in western New England. The triple-point low will help create some shear, but overall this factor will be more on the marginal side.

With all of that said, the farther west you go in New England, the higher the severe chance will be. A big uncertainty that remains is how far east stronger storms can push in New England before beginning to weaken. The farther east you go, the more likely clouds are to be stubborn. The amount of instability present will also steadily drop moving eastward. Severe storms are not expected over Maine.

Strong winds and large hail will be the primary threats. With a triple-point low in place generating some shear, there’s a low risk of tornadoes as well. With multiple rounds of storms expected, some minor and localized flash flooding will be possible should multiple storms move over the same area.

The system's cold front will cross New England by Sunday morning. This will bring in a cooler and much less humid air mass. The upper-low will basically be overhead, which will lead to a mainly cloudy day with some showers around. Showers are generally more likely and more numerous across the northern tier with just spot activity expected across southern and central New England.

We've talked about it all week, and now the chilly, cloudy and wet week is upon us. For those looking for the start of summer weather, next week is a lost cause, plain and simple. Conditions will likely remain unsettled for much of the week with persistently cool temperatures. A soaking rain is possible around midweek. Right now, Thursday is favored to be a washout, but timing can still change at this point.