Changes - less snow

The models have maintained their forecasts through the 06z runs, of which looked great for 12+ amounts across much of southern and central New England away from the coast. The major disagreement has been in the speed/strength/track of the surface low. The GFS has been an outlier to the west for a while, but has been consistent. Its forecast would give over 14 inches to the area. The NAM has been less consistent, and further east but has support from the other guidence. Now, the 12z NAM has shifted east slightly, and the GFS followed with a notable jump east along with a faster weaker low. A sharp cutoff in precip has always been a concern with this storm, but mainly for eastern NY. Now the problem enters VT and western NH. A good front end dump is still likely between 3am and 6am, however the 1000-850mb low collectively takes longer to ramp up, removing wrap around accumulations from the forecast even north of the MA pike and moving the deformation zone northeast into SE NH and southern ME. Uncertainty continues considering the just recent change in the model forecast. Still have support from the 9z SREF mean for over 8 inches of snow, but a lot of range still exists in the individual ensembles - anywhere from 0 to 30 inches. The Euro and GGEM - both on the eastern side of the consensus have recently made a slight shift west. However, the consensus now for a more eastern track, with no GFS forecast to say otherwise lends itself for higher confidence on lower accumulations of a Worcester, MA median. A speedier storm, taking longer to strengthen will also remove the potential for any 18 inch amounts in New England, with a max probably no higher than 14 inches.

Focusing in on Keene:
Pros for snow -

High snow to water ratios. Forecast soundings indicate that dendritic snow growth will still be alright here in Keene, although best snow growth will likely be across central and east central NH. Snow to water ratios will start off relatively low considering day time heating today bringing temps into the low 40's will mean temps around freezing when the first flakes begin to fall. However, continued nocturnal cooling along with evaporational cooling early on will drop surface temps into the upper 20's. Maximum ratios of 15:1 are possible between 7am and 11am - good, however timing displaced slightly from the height of the storm. Averaged out, ratios of 13:1 to 14:1 are possible.

Dry slot should miss us to the south. The 700mb low is still expected to cross the Cape and RI limiting mid level drying to southern CT into RI and eastern MA and allowing steady precipitation to be maintained through the height of the storm with keep showery precip away from the area.

I suppose it also should be noted as a pro for snow that the NWS is maintaining a winter storm watch (with intentions of upgrading to a warning when inside the appropriate timeframe) and is currently calling for 7 to 13 inches here in Keene.

Cons for snow-

The track of the 1000-850mb low will be too far east, too fast, and too weak for prolonged heavy snow in the area. Main front-end snows will be east of I-91 with a sharp cut off at that point. Then wrap around wont occur until the low is heading off towards Nova Scotia, limiting additional signficant accumulations to Maine and maybe eastern NH.

Regarding the cut-off in total accumulation, Hillsborough county in SNH has a very good shot at 10+ inches for all locals. Based on the latest model runs, this 10+ area will drop off quickly, starting near Jaffrey and ending with only an inch or two of snow for areas between Bennington, VT and Albany, NY. With Keene in between the cut-off, a slight shift in the storm could make the difference between 3 inches and 10 inches. Im essentially going with a compromise of the two values, with a final forecast of 6 to 8 inches. Totals even within the city of Keene could range more than usual. portions of eastern Keene could see 8 to 11 inch amounts while western Keene sits at 6 inches. In Cheshire county, totals will definitely have a wide range, possibly as much as by 10 inches.

Storm timeline:

Light snow starting by midnight with little or no accumulation through 3am.

Snow becomes moderate to heavy at times 3am to 7am with 3 to 4 inches of accumulation. - (agrees with NWS forecast of 2 to 4).

7am to 3pm: Moderate snow ending by 3pm. 3 to 4 inches of accumulation. - (NWS has 5 to 9. Forecast depends on how fast the low strengthens).

Some light snow showers possible through Monday evening but with no additional accumulation.

Total accumulation: 6 to 8 inches west of the Ashuelot, 7 to 10 inches east of the Ashuelot.

>/= Delay? Likely considering heaviest snow should target morning commute.
Cancellation? Will depend on whats expected for additonal accumulations after 7am. If we can pull off another 4 inches after 7am, then a cancellation is likely.