Fabulous discussion from Upton. This event is certainly nothing to ignore or sneeze at...1-2" per hour rates likely with all of the lift in the dgz and relatively unstable columns, as well as solid fgen just underneath the dgz.
Still some questions as to exactly where bands of highest QPF
will set up on Monday as fast-moving low pressure passes to the
south. GFS/RAP, which were performing well with the position of
banding in the Plains states this afternoon, show this axis
passing just S of NYC/Long Island, while the latest extrapolated
HRRR aims for Long Island, and the NAM/SREF set up more
squarely over the entire area. Taking a blend of these and
accounting for usual southerly model bias with frontogenetically
force banding suggests this axis will skirt NYC and Long
Island, running roughly from RDG-JFK-MTP.
NAM 2m boundary layer temps may be a touch cold and tempered
them with slightly warmer MOS, but the end result per resulting
wet bulb temps still yields a precip type of snow, but with
perhaps slightly lower SLR in urban NYC metro and NE NJ.
Meanwhile, fcst soundings indicate a quick-hitting 3-4 hour
period of moderate to even locally heavy snow possible, with
snowfall rates of as much as 1-2 inches per hour as lift is
maximized in the dendritic snow growth region, while lapse rates
will be neutrally stable, approaching moist adiabatic. Those
snowfall rates should overwhelm the warmer ground temps and
allow snow to accumulate on roads mainly during and just after
the AM commute. When all is said/done, expect 2-4 inch
accumulation along the northernmost portion of the CWA, and 3-5
inches for NYC metro, Long Island, and coastal CT. There is
potential for total accumulation of 6 inches in the higher
elevations of NE NJ west of the Garden State Parkway, perhaps
extending up along the Rockland/Orange border. Total
accumulation on roads likely to be less than the storm total
snow, so previously issued advisories for late tonight into
early Mon afternoon remain in effect.