Fake Spring 2.0? Models converging on warmer pattern change in NYC

Winter is not over…yet. 

Forecast model guidance is in good agreement that the weather pattern will trend much warmer in the Eastern United States from late February into early March. Temperatures could rise well above normal starting late next week, offering us yet another taste spring – is it real, or do we have another “fake spring” on our hands?

The forecast for warmth can be traced back to the presence of a strong Pacific Jet stream, which is flooding the United States with warm air from the west. Without any strong high pressure systems to our north to keep the air away, warmth surges eastward into the Plains and Central United States first and then eventually makes its way to us. 

The warmth will be further exacerbated by an amplifying pattern in the mid and upper levels of the atmosphere. Most ensemble guidance shows this quite well, with a deep trough forming in the Western United States and ridging amplifying in the Eastern United States. South and westerly wind flow will encourage warmer than normal air to advect towards our region. 

As a result, most model guidance suggests that temperatures will average much warmer than normal from late February into early March. The first weekend of March in particular could be quite warm with temperatures 10-15 degrees (perhaps more) warmer than normal. Needless to say, there will be a few days within this pattern that will have us feeling like spring is finally here. 

Not so fast.

Looking under the hood, there are changes occurring aloft that suggest the caution flags should be raised. The stratospheric polar vortex – which is the constantly existing vortex tens of thousands of feet above our heads – is weakening considerably in what may be its last gasp for the season. As this occurs, high-latitude blocking may develop in mid-March (pictured by oranges and yellows in the higher latitudes on the below image).

Ensemble guidance is already hinting at this. As we have discussed several times this year, when blocking high pressures develop over Greenland and Canada, they can displace cold air southward towards our area. Accordingly, there are hints of a colder pattern shift in mid-March that could keep winter weather on the table for at least a few more weeks. 

For now, there are no immediate storm threats signaled and major cold isn’t expected. But given what we see in the long-range, it appears that this upcoming warmth could be just another fake spring. 

We will see!