Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
130 PM EST Tue Mar 06 2018


Prelim Day 1 QPF Discussion
Valid Mar 07/0000 UTC thru Mar 08/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1...

...Great Lakes/Ohio Valley to East Coast...

The focus for the rest of Tuesday and all of Wednesday will shift
from the Upper Midwest to the East Coast. The powerful cyclone
over the Midwest will gradually shift downstream and decay/fill
over the Great Lakes before partially reforming over the region,
while upper dynamics from this system round the base of the upper
trough to induce a coastal low near the DelMarVa. This surface low
will deepen rapidly by 5-10 mb, while moving up the coast toward
Long Island. This will set the stage for back to back late season
winter storms to impact portions of the Northeast. Most of the qpf
is anticipated in association with this developing Nor'easter, as
an increase of Atlantic moisture streams in from the east and
flourishes on the north and west sides of the intensifying system.
WPC followed a 5 way blend for qpf, 12z gfs, nam conest, nbm and
href mean with the 00z/06 ecmwf. This blend focuses 1 to 2 inch
areal avg qpf amounts with locally higher values from DE/nern MD
through eastern PA/all of NJ into NYC/southern Hudson Valley/Long
Island and perhaps into southern New England. Meanwhile, other qpf
highlights include possible focus from the coastal low to the
500mb circulation over MI along an inverted trough axis and
possible scattered showers/storms from the southeast through FL
this evening through midday tomorrow. The difficulty with the
forecast is ptype from the Mid-Atlantic up into the Northeast or
where the rain/snow line will set up. The surface low track is
absolutely critical and the latest trend with the 12z guidance is
a little left, closer to the coast, which may shift the rain/snow
line over the major metro cities from PHL to NYC to BOS or north
and west or the metro areas and I95. For more on this difficult
wet snow forecast, please refer to the latest qpfhsd.

Musher