Thursday will be a very busy weather day for New England as intense heat and humidity build throughout the day with potent thunderstorms erupting during the afternoon and evening.
The system will arrive in northern areas first before energy slides southward. This means the further south you go in New England, the higher the chances of seeing severe weather on Thursday as the best ingredients to build potent storms will be present in the afternoon. At this time, it looks like the southern two thirds of New England are in the cards for severe weather. The storms are looking to be hit-or-miss. Not everyone in the yellow area below (or green for that matter) will see a storm. This is bold as it needs to be emphasized that this is unlikely to be a solid line of storms.
The biggest question will be cloud cover. If the day remains mostly cloudy to cloudy, it will limit instability and therefore limit severe thunderstorm potential. Should clouds be able to break up in the early to mid afternoon, it will excel severe thunderstorm activity.
The impacts below pertain to the areas in yellow on the map above.
IMPACTS
As of now, all five major hazards that come with strong to severe thunderstorms are on the table. Those five hazards are wind, lightning, hail, tornadoes and flooding. As per usual with severe weather in New England, the biggest severe threat will be straight line wind gusts. Many storms will likely have embedded strong gusts.
Torrential downpours and flooding will also be a bigger threat. The region will be in a tropical-like air mass, and PWATs (precipitable water, which we discussed recently in this article) will once again be over 2 inches, and in some places, well over 2 inches. This, along with the fact that storms will be slow moving, means that storms will be capable of very heavy rainfall rates.
While not widespread, localized areas that get stuck under the storms could see several inches of rain. Flood watches have been posted for southern New England, Vermont, most of New Hampshire and much of western Maine. Despite northern New England not seeing as much severe weather, the region has just as much of a chance to see torrential downpours and flooding rains.
Small hail is also a threat, though to a lesser extent than winds and flooding. There is also a low risk of tornadoes across a portion of New England. The setup will allow for isolated, rotating supercell thunderstorms to develop. The primary risk for this to occur will be across Massachusetts and southern New Hampshire. Again, this is a low risk, a 5% chance across the areas mentioned previously, however, 5% is still more than most thunderstorm days in New England.
TIMING
A warm front will lift through the region in the morning, this could trigger some downpours and storms during the morning hours. These early showers and storms will primarily be seen across northern New England and should remain sub-severe, although some flash flooding could occur. The afternoon line that fires ahead of a cold front will be the main concern. Storms will likely be firing around the region throughout the afternoon into the evening. Activity will begin to diminish after sunset with everything wrapping up by 9 to 10pm.
HRRR model showing a line of storms moving southeast through Massachusetts around 5pm:
The moral of the story is to keep an eye to the sky all day if outdoors.
HEAT
Despite the fact that thunderstorms have all but stolen the weather headlines for Thursday, intense heat will build across southern New England during the day. A heat advisory is in effect for southern and central New England. Heat index values will approach 100 degrees as most of the day will be dry.
Can you do a piece centered on the weather terms relating to magnatude of conditions? For the average lay person, terms like isolated vs scattered and watch vs warning are sometimes confusing. Also confusing is the difference between partly cloudy and mostly sunny.