Weekly outlook: Warmth, thunderstorms, and more warmth

The well-advertised warmup we previously wrote about has finally arrived, and it’s packed quite the punch. Away from the immediate coast, temperatures have hit 80 degrees on consecutive days (yesterday and today), and if clouds don’t increase too quickly tomorrow, we could make it a 3rd straight day.

The average high in Central Park on May 4th is 67 degrees. So far today, we’ve already hit a high of 85 degrees. It’s definitely an early preview of summer, as a deep southwest flow has taken over the weather pattern, stemming from a large ridge of high pressure dominating most of the country — particularly the Southeast States and streaming through into our area. A large area of high pressure to our south is the most efficient way to generate warmth, as the counterclockwise flow around the high pumps up the warmth from the Gulf.

With the core of the ridge being near our area and frontal boundaries being well to the north, skies have remained mostly sunny, except for a few cumulus clouds here and there due to the heating of the ground. This will remain the case through the rest of the afternoon, as temperatures generally hold in the low 80s and falling to the 60s and 70s this evening. Areas closer to the coast have had to deal with a sea breeze, as temperatures have held in the 60s and 70s, and will fall into the upper 50s and low 60s this evening. This will also be a general theme during this warm stretch.

While there are initially decent atmospheric conditions for radiational cooling this evening/tonight, an increase in clouds and the warm airmass should keep low temperatures in the mid 50s for the most part — with low 60s in Urban areas.

Moving towards tomorrow, more clouds and a few scattered thunderstorms is a possibility.

The top of the ridge is poking into Canada, where there is still plenty of cold air in-tact. This clashing of temperatures has led to the development of a cold front. Due to the strong ridge, it will have a hard time poking its way southward, but it will eventually take a south of east track and head close to our area tomorrow.

Before it does so, we can expect another warm day tomorrow. We’re thinking that due to the slow movement of the cold front, the morning through parts of the early afternoon will still have some sunshine. Considering the warm airmass, temperatures could spike back into the 80s again.

However, after this continued early summer preview, the cold front will push its way into the area and ruin the party with an increase in clouds and a chance of thunderstorms during the afternoon. The cold front will allow for lifting in the atmosphere, as well as stronger moisture convergence and pooling, especially due to the fact that we’ll have had a southwest flow for three days in a row — at some point, that persistence will allow more low-level moisture to make its way into the area. While tomorrow won’t be that humid, it will feel a bit muggier than it was today.

What may also help for the formation of thunderstorms is the sea breeze. Once again, coastal locations will hold in the 60s and 70s. But now that we have the lift from the front, the seabreezes converging with the southwest winds just inland will allow for additional convergence just inland from the coast and could also cause problems during the afternoon.

The wind fields look pretty slow tomorrow, which should prevent a severe weather outbreak, and should also keep storms slow in motion. However, there is just enough instability for a few thunderstorms, and the moisture fields, combined with slow movement could lead to a training of thunderstorms with heavy rain/flash flooding hitting the same areas. Also, if we do get enough breaks in clouds during the early portions of the day, there could be enough organization for a few strong thunderstorms with tall cumulus structures, especially considering there is some wind shear in the atmosphere (a change of wind direction in height) despite the weak wind fields overall. This could lead to a few strong wind gusts — but as mentioned before — severe weather is unlikely and hail is not a threat.

The front’s slow progress will mean that clouds and perhaps a few showers will linger through tomorrow evening/tomorrow night. Winds will shift back to northerly and we will dry out for Wednesday. Temperatures should fall to the low to mid 50s on Tuesday night.

Wednesday will initially have some clouds due to the cold front’s close proximity, but sun will eventually prevail and temperatures will climb back up into the low 70s. The ridge’s influence won’t completely leave the area, which is why temperatures aren’t all that cold behind the cold front.

In fact, there are persistent modeling signals that more strong return flow from a high pressure could come back for the latter part of the week and the weekend. Temperatures will rise into the mid to upper 70s on Thursday, but more 80s are expected for Friday and the weekend, provided a tropical disturbance to the south doesn’t give us too many clouds. It has similarities to the look we we had yesterday and today, which gives us increased confidence in warmth. Sea breezes along the coast will still generally be an issue during the warm days, but on the bright side, pleasant temperatures in the low 70s can still be had this time of year, even with a sea breeze.