Evening Zones: From Spring to Summer

Good evening, everyone! We hope you enjoyed this pleasant, but very windy day. This wind was actually one of the signs that big warmth is about to come, as this wind is a result of the pressure gradient between the departing low pressure and incoming high pressure that is on the leading edge of a large ridge that will bring us warmth. As high pressure moves in this evening, the gradient will be “pushed” off the coast and our winds will be able to calm somewhat after sunset. Skies will remain clear as well, with lows in the upper 40s to low 50s for the most part, with perhaps mid 50s in Urban Areas and low to mid 40s in the Interior Valleys and Pine Barrens.

A large trough in the Western US will allow a ridge to continually pump in the East, and as the storm system off the coast continues to depart, that will give more room for the ridge to pump up into the region further. Additionally, a large disturbance will be moving into the Plains and then the Great Lakes, which will increase the southwest flow out ahead of it, which will further advect warmer temperatures and more humidity. This will allow for more warmth and humidity as the week goes on.

On Tuesday, we see that ridging has moved into the region, but the core of the ridge remains to the west and the south.

Today's NAM model valid for 2:00pm on Tuesday shows 850mb temperatures between 10-12C, which could support temperatures approaching 80 degrees.

Today’s NAM model valid for 2:00pm on Tuesday shows 850mb temperatures between 10-12C, which could support temperatures approaching 80 degrees.

But notice that the flow aloft is still northwest at 850mb, 500mb, and 300mb, as the departing upper-level low associated with the storm system on Saturday still has not completely cleared Northern New England. This will prevent a true scorcher and also lead to humidity being very low, but 850mb temperatures between 10-12C plus downsloping flow should lead to temperatures approaching 80 degrees for the most part. This flow may be able to stop seabreezes as well, so the coast should also see highs in the upper 70s to around 80. The only exception will be Eastern Long Island — particularly the North Fork — as this flow will usher in some air from the Sound and keep temperatures a few degrees cooler. The ridging building in should assure mostly sunny skies, though that vorticity ripple to the northwest may mean an increase in high clouds for northern NYC suburbs.

Today's NAM model valid for 2:00pm on Wednesday shows more ridging building in and flow aloft turning westerly, leading to more warmth than on Tuesday.

Today’s NAM model valid for 2:00pm on Wednesday shows more ridging building in and flow aloft turning westerly, leading to more warmth than on Tuesday.

Moving into Wednesday, notice how the core of the ridge begins to move overhead as the upper-level low completely departs. This means temperatures aloft are inherently warmer. The flow has also turned westerly aloft and southwesterly at the surface. This along with the component of the ridge allows for more heat and humidity to advect into the region. Thus, we are expecting high temperatures generally in the upper 80s for most of the region, though surface winds being southwesterly means that areas east of NYC will have some onshore component, so temperatures may hold only around 80 for those spots. The ridge should again assure mostly sunny skies.

Today's NAM model valid for 2:00pm on Thursday shows completely uniformly southwest flow, allowing for even more warmth aloft and for a truly hot and summery day.

Today’s NAM model valid for 2:00pm on Thursday shows completely uniformly southwest flow, allowing for even more warmth aloft and for a truly hot and summery day.

Take a look at how this progression evolved over the next few days and how the heat has to maximize for Thursday. Notice in the above image how as that disturbance moves into the Great Lakes, the flow out ahead of it becomes uniformly southwest and also much faster as the height gradient between the disturbance and the ridge tightens, which will further allow more heat and humidity to advect into the area. Thus, 850mb temperatures really spike to around 18C, which may support widespread highs in the low 90s for most of the region! Humidity will also be somewhat high, but not necessarily unbearable — but still quite a summery day is in-store. Again, though, this southwest flow places areas east of NYC in an onshore component, so temperatures may hold around 80 degrees in those locations. A few high clouds may stream in ahead of the disturbance, but otherwise mostly sunny skies are anticipated.

Eventually, a cold front associated with that disturbance may move through on Thursday night, sparking some isolated thunderstorms and cooling things off a bit and lowering humidity for Friday. though downsloping behind the front may lead to temperatures rising into the low 80s anyway. A blocking pattern will return for the weekend, which will result in upper-level confluence to our north, meaning surface high pressure to our northeast and thus a chillier, onshore component with temperatures falling back into the upper 60s. As of now, Saturday at the very least looks pleasant, though a disturbance may try to approach the area on Sunday or Monday.