Friday/Saturday Storm – Wind But No Snow?

Most of our computer models this morning have some good news for travelers Friday. The GFS and NAM both show the storm that develops will stay far enough offshore on Friday to spare us from any appreciable rainfall during the day. On the 6z GFS you can see one batch of precipitation over Cape Cod and Maine associated with some DCVA (differential cyclonic vorticity advection) and some low level warm advection (look at the thermal packing at 850 mb along the eastern Massachusetts coast). A second batch of precipitation from Watertown, NY south toward Sussex County, NJ is associated with a strong 500mb vorticity maximum. The 6z GFS does slide some precipitation into CT after 10pm Friday night which could fall as a little bit of light rain/mixed with snow in the hills.

One important difference in the GFS/NAM from the Euro is that at 12z Saturday the Euro has the surface low in the Gulf of Maine while the GFS and NAM have it north of Caribou in New Brunswick. If the surface low gets captured by the mid/upper level lows and it stalls south of Maine then there is a greater chance at seeing some accumulating snow in southern New England.

The GGEM and UKMet agree more or less with the American models and keep this thing far enough north to spare us from a more significant wraparound event. That said, the 00z GGEM does bring in some moderate rain during the day on Friday. As is sometimes the case the far outlier/wrapped up Euro solution doesn’t seem to be the way to go. A consensus forecast approach keeps this storm progressive and out of our hair (with limited snowfall) by Saturday morning.

One other issue for Saturday will be the winds behind this storm. On the 6z NAM BUFKIT sounding you can see a well mixed boundary layer tapping into some of the strong winds just off the earth’s surface. A strong pressure gradient in the storm’s wake should lead to gusty winds over 30 mph and possibly 40 mph on Saturday. Notice the lapse rates to the left from 850mb to 950mb is nearly dry adiabatic (9.1ºC/km). If the storm trends stronger or cuts off further south these winds may be stronger.

Bottom line – here’s what I’m expecting

  • No snow accumulation in SNE outside of the Berkshires (some upslope)
  • Wind gusts to 40 mph Saturday morning
  • No precipitation after 12z Saturday (dry at BDL/ORH/BDR/PVD/BOS)
  • Rainfall through 12z Saturday of 0.25″ to 0.5″ at BDL



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