Sunday, March 24, 2013

Forecast for Monday, March 25, 2013

We're not confident in warning criteria snow in South Jersey. It could happen. But 2 of the "big 3" (GFS and Euro) don't support warning criteria snowfall in the warning area. The NAM is the only model and its performance has been less than stellar. But it does have a bit of support with evaporational cooling looking a bit more likely with this event which may cool the column just enough, although it is a truly borderline situation. It may end up being right but there's a lot going against a larger snowfall. But with this being just a few hours away from beginning and the slight possibility of an imminent warning criteria (4 or greater inches in Southern NJ) snowfall in Southern NJ, the National Weather Service has chosen the warning route. It is an extremely difficult call with a model spread of 0 to 10 inches in late March.

The Euro has trended significantly drier for the event with less than a half inch of precipitation in the city and less than inch at the Shore. The GFS contains greater moister than it did in prior runs. The NAM cut back a bit, but has significant precipitation and supports significant snow.

Given the tremendous amount of model inconsistency and the lack of agreement, any forecast that's out there has low confidence...ours included. That said, when you're expecting dynamics and banding to produce snow across the region in late March, during the day, it's not the most conducive setup. This is why our expectations lean towards the wetter vs. snowier guidance, at least for now. We will of course follow the 00z suite closely although we are nearing the nowcast  point.

Could a significant snowfall happen? Yes, it is possible. But for now it's a clear outlier solution (meaning unlikely compared to most projections). Everything has to come together perfectly and in the past, modeling inconsistency less than 24 hours out typically is not a good sign for the big snow outcome to play out, especially when modeling outcomes are as different as they are and you have large forecast ranges. The last three times we were down this road the lesser amounts won out or we were even too high. If this storm tracks far enough north and can really cause intense rates of precipitation, than heavy wet snow may win out. But even if it is wet snow, can it pile up on trees and grassy surfaces? Well surface temperatures would have to be in the 33-36 range. Anything higher and it is unlikely to be anything of significance.

We will continue to analyze and update our forecast. If we do see locations of greater than 3 inches of wet snow accumulation, isolated power outages would result from the weight of the snow.

No doubt a storm where our hair will be turning gray! A huge bust potential and the high possibility of a few surprises.