Excellent discussion from the NWS a few minutes ago. They're sticking with the forecast, but note bust potential near Philly/SNJ on the low side and NW NJ/NE PA on the high side (they have lower forecasts right now). Also confirming what I had said would likely be the case - snow/liquid ratios above 10:1. That's 10" of snow for every inch of liquid precip equivalent that falls - that's typical around here - we had 5-7:1 in the more recent storms as we had crappy snow growth aloft and melting as flakes fell through above 32F column.
National Weather Service Mount Holly NJ
848 AM EDT Wed Mar 21 2018
NEAR TERM /UNTIL 6 PM THIS EVENING/...
8 AM checkin. STS snow grid as posted on PHI web site and in
briefing pkgs conts as is and is from 8AM today through 8 AM
Thursday and does NOT include what occurred between 8 AM ydy and
8AM this morning.
No further briefing pkgs today but we will update the STS as it
becomes apparent to us that amounts will differ more 2 inches
from our
fcst. Will we get 10-12" in PHL? Possibly not but its
going to be quite a mess. We already have a widening areas of
MDT snow developing eastern PA and nw NJ just west of the I95
corridor and its only 12z with many reports coming in now of 2"
snowfall in the last several hours.
Also fwiw...temps rose into the upper 30s overnight in the I95
corridor when
pcpn quit and still the ice/snow mix held strong.
Ground has been cooled.
We will be issuing
LSR`s only for 1/
hr snowfall accumulations
and
glaze reports elsewhere that totaled 0.1 or greater. Lets
continue sending those reports to us via our
skywarn or social
media accts. Both the
glaze overnight and the storm total snow
and lets us know how the roads are doing and if any
power
outages.
Collapsing thicknesses as
pcpn now is changing to sleet and then
snow most of our I95 area except the coast this morning.
Synoptically: no
chg from pattern recognition. A big event is
unfolding and we just need to be patient. Significant nearly
stationary banding now evident N central MD to eastern Berks
western Bucks County to near NYC. EVERYONE will share in snow
but the main axis of the S+ should be
vcnty MQS-CKZ-SMQ (Chester PA to near Doylestown PA to Somerville). Higher
amts than forecast are possible in the NNJ part of our
fcst,
particularly Northampton, Warren, Hunterdon, Morris, Somerset
but we`re not raising at this time until we know for sure what
we already have at 230 PM. If we update...it will be STS (short term statements) only
and posted to our office winter
wx web page and also
SM.
Inverted
trough developing from the developing primary coastal
low through through Ches Bay and that can aid lift to its
northeast. Monitoring.
Regardless of snow amounts, SUBSTANTIAL impacts, including
power outages and additional tree damage, are
likely due to a
combination of
heavy snow, strong winds,
blowing and drifting
snow.
Mesoscale wise: please note we are aware of a typical Berks
county downslope shadow in western Berks. I can see storm totals
ranging 7" western Berks to 15" near Huffs Church in the high
terrain far eastern Berks. No changes yet but we are aware of
the potential.
Snow ratios: in 3
hr increments 12z tdy-07z tonight.
PHL 9,10,11,12,12,12 to 1 using snow ratio blender.
In the cldr
ptn of storm e PA/NNJ
vcnty I78 10,12,12,12,12,12
to 1 with Poconos slightly higher snow ratio. So even if
qpf
were to decrease this
aftn, snow ratios will permit greater
hourly
accums.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
The low will begin to move northeast away from the region,
bringing a gradual end to the snow but still expect an easy 1-3"
after 8 PM. For the most part, expect any significant
accumulations to be over with around 2 AM. Light snow showers
may linger into the early morning hours, especially across
northern NJ. For low temperatures, have gone on the lower side
of guidance in anticipation of a widespread
snow pack by that
time.
https://forecast.weather.gov/produc...&format=CI&version=1&glossary=1&highlight=off