2:30 p.m. update: Today’s European model run develops a storm close to the coast and would suggest some rain changing to wet snow for the D.C. area Sunday into Sunday evening. There’s still lots of uncertainty in what may actually develop but it’s something we’ll be watching closely…

Original post

We declared winter over over a week ago* and we stand by that. But, a brief spell of chilly weather this weekend might allow a bit of wet snow to fall over parts of the region on Sunday, coinciding with the spring equinox.

The chances of seeing snowflakes are low, probably around 30 percent. And the chance snow accumulates is even lower, 10 percent or less.

Models show a cold front passing through the region on Friday, which sets up a chilly March weekend. Highs on Saturday may struggle to exceed 50 with lows in the 30s Saturday night.

Things turn a bit interesting on Sunday. A jet stream disturbance will zip through the region and, depending on its exact track and intensity, may produce some light precipitation.

Rain showers are most likely but with some cold air at high altitudes, a bit of conversational snow cannot be ruled out, especially in our colder suburbs. Given air and ground temperatures above freezing throughout the region, accumulation is highly unlikely.

The only scenario for accumulation would be if a stronger storm develops off the coast, draws in more moisture, and produces heavier precipitation – which would cool the air. And, even in this scenario, the accumulation would be mainly on grassy areas given the warm ground.

The European model simulated a strong coastal storm for Sunday yesterday, but has since shifted the storm track far enough offshore such that little or no precipitation falls in the D.C. area. But, the low pressure positions represented by its larger group of simulations (known as its ensemble) are close enough to the coast and the event is far enough into the future that shifts are still possible. So this bears watching.

The group of simulations from the GFS model, known as the GEFS (Global Ensemble Forecast System), mainly develops significant storminess too far off the coast to be a concern:

However, one member (e6, see below) of the GEFS shows a snowstorm Sunday, as shown below:

The bottom line is that we will briefly shift into a cooler weather pattern over the weekend into early next week which could produce some spring snowflakes if, and only if, everything comes together just right – which is a long shot.

* Note: If it snows on Sunday, we will surely get teased for having declared winter over.  But note our declaration stated “a cold day or freak snow event can’t be ruled out”.  For our declaration to “bust”, accumulating snow remaining on the ground for at least 12 hours would have to occur, given our criteria for the end of winter.