This entire week has been quite unsettled as we have had showers and t’storms across the region every single afternoon. While not everyone has seen action, several places have been hit several times this week with showers and t’storms and as we move into Friday and into the weekend we will remain in a similar pattern, in fact, this pattern should remain in place through next week. However, the point of this blog post is to discuss the weather for Friday. You may hear forecasters every now and then (or even so often) say, “this is a highly complex weather forecast”…well this is yet another case of that and, well b/c it is. As much as we know and understand the weather and the atmosphere and how they work, both are still a highly complex science and sometimes there is just so much chaos going on in the atmosphere that forecasting to certainties and exacts can be extremely difficult at times. This is why I am always in favor of explaining the situation in as much detail as possible to hopefully help the reader have an understanding of the situation.
Anyways, this past week we have been dealing with several different meteorological phenomena’s which have lead to some very difficult forecasts, some turning out good, and some getting completely wrong. As we move through the remainder of tonight and through the day tomorrow, the forecast won’t necessarily become much easier, however, confidence is increasing on several weather events we will see across the region.
During Wednesday, including the overnight period, a weak backdoor cold front (cold front which moves into the region from the north, northeast, or east) slid southwestward across the region and by Thursday morning, this weak boundary had washed out across central CT. Typically when cold fronts move through, we usually see a refreshed airmass, it’s cooler and less humid. Well, that wasn’t the case this time. This front, as mentioned was very weak, and the cooler temps/dewpoints actually lagged well behind this front and you’d have to look all the way into northern New England to find this refreshing air. During the day today, the washed up front left a boundary in place across the region and that was the focus for some afternoon showers/t’storms that popped up across the region.
To our west, a deepening trough has been slowly sliding eastward dragging a cold front east as well. As the trough/front slowly slide eastward, a surface area of low pressure has been developing and this will slide to our northwest during the day tomorrow. As this occurs, the washed up backdoor cold front over the area will actually retreat north as a warm front, in fact this process is already occurring. With the system strengthening to our west we have seen stronger winds aloft move into the region, especially in the lower levels of the atmosphere, these factors will lead to the development of showers and t’storms during the overnight hours. While instability is very marginal, winds aloft are increasing so we can’t completely rule out a strong storm overnight with some gusty winds. The main threat though will be torrential downpours leading to pockets of flash flooding.
Now, as we move into Friday morning, there still should be numerous showers and perhaps some t’storms around. After this activity moves out, this is where the forecast becomes much more complex and challenging. Winds aloft will be quite strong tomorrow, also, with the possibility of the warm front being close-by, this will lead to some very high helicity values (change of wind direction with height), across the region. There should be lots of clouds present, however, some computer model guidance is showing that there may be breaks of sun late tomorrow morning, especially across western CT/MA. If we are able to get any sunlight, given how dewpoints will be into the upper 60’s to lower 70’s, and the potential for temperatures to get into the lower 80’s, this will lead to a fairly unstable airmass tomorrow. If we are able to achieve sufficient destabilization, the threat for more t’storms in the afternoon will vastly increase. Given the presence of very strong wind shear and a very strong system to our west, the threat for strong to severe t’storms would exist. Now, conditions right now don’t appear to favor widespread severe weather, in fact, we are probably only looking at an isolated threat for a few of the storms to become strong to severe. Any stronger storm will have to be closely watched though as it would have the potential to acquire rotation and the threat for an isolated tornado would be in the cards. Again, the confidence in this right now is low b/c there are major questions with how unstable the airmass will become tomorrow. Basically, the more sun we see tomorrow, the higher the threat for t’storms and the higher the threat for some of these storms to become strong to severe and be capable of damaging winds, large hail, and perhaps a tornado. If we see little sun, the threat for t’storms will be much lower and the threat for severe storms will be extremely low, although still would have to closely monitor any storm that would develop. Besides instability, the tornado potential would also depend on where the front front positions itself. If the warm front is able to get well into northern New England, well then we would have less helicity values as the directional component to the wind would decrease and winds aloft would be blowing from the same general direction.
Once again, a severe weather outbreak is not expected at this time, however, the threat for t’storms will exist and if we see enough sunshine to really destabilize the atmosphere, the threat for t’storms and threat for some of these to become strong to severe increase. Less or no sun, low threat for storms and even lower threat for any of these to become strong to severe.