A Week of Storms

I love my job. Nights like tonight make it even better. Super Bowl on TV with 3 winter storms to forecast! Storm number 1 on Monday isn’t a big one but I do think it will be disruptive.

gfsNE_250_spd_018

A strong jet streak over northern New England (nearly 200 knots!) is going to produce a fairly sizable direct thermal circulation over southern New England in the right entrance region. Classic QG forcing with an advancing shortwave (and strong cyclonic vorticity advection) overhead.

Indeed, right around 12z model omega fields show a modest amount of lift pretty high up in the troposphere (around and even above 500mb). While the amount of lift isn’t terribly impressive the atmosphere is fairly “juiced” up with a deep layer of high relative humidity.

18z GEFS PWAT Anomalies (Valid 12z Monday)

18z GEFS PWAT Anomalies (Valid 12z Monday)

The 21z SREF mean has about 0.45″ of liquid in Bridgeport which is more than previous runs. In fact in the dProg/Dt plume you can see how the runs are becoming a bit juicier as time goes on.

sref

 

The question is just how much forcing and moisture do we bring in. Additionally, how good will the snow growth be? The 18z NAM showed a period of very good/efficient dendrite growth tomorrow morning – along the shoreline it was excellent though a bit strange!

nambufkit

 

Notice the omega crosshair in the snow growth zone around 500mb. That’s pretty unusual to see since normally good lift around 500mb is above the dendritic growth zone. In this storm the atmosphere is warm enough (and moist enough) for good snow growth to take place pretty high up in the troposphere. With temperatures near 0C in the boundary layer we could get a period of really large aggregates.

So here’s the bottom line. Lift doesn’t look terribly impressive and I don’t see any signals of intense mesoscale banding (i.e. no strong frontogenesis) so that initially makes me a bit gun shy. However, I think a lot of that is compensated for by unusually high moisture content in the atmosphere, decent snow growth (efficient precip/snow production) along the shoreline, and enough synoptic scale lift (strengthening jet streak in northern New England) to get the ball rolling.

chart_3 (5)

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