Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
1242 AM EST Fri Mar 02 2018


Prelim Day 1 QPF Discussion
Valid Mar 02/1200 UTC thru Mar 03/1200 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1


...Eastern U.S...
Lows moving through the DelMarVa and offshore the NJ coast should
merge and move northeast becoming a vigorous cyclone within the
climatologically favored area for March off Long Island through
early Saturday as an upper level low closes off overhead.  Warm
advection is contributing to the initial expansion of rainfall
into the northern Mid-Atlantic states at this time, shifting into
southern New England early on.  This event will become more
intensely focused as the coastal low develops which strengthens
frontogenesis in the 850-650 hPa layer.  These ideas fit well with
the previously issued WPC forecast, which we retained.  The
biggest adjustment needed was to lower amounts per the recent
guidance across northeast NY and northern New England.

The 00z GEFS-based QPF re-forecast data, based on analog events,
suggests a swath of 2-5" areal average QPF across some portion of
the Northeast.  Rules of thumb based on instability, moisture, and
low-level inflow available across southern New England support a
4-6" range.  Per information received from SAB/NESDIS, the
December 11-12, 1992 nor'easter is a particularly good analog for
the precipitation expected for southern New England -- 4-8" fell
across southeast MA during that intense nor'easter.  Other
possible analogs pointed out by the BOX/Taunton MA office were the
March 7, 2013 and April 1, 1997 events.


...Western U.S...
A deep layer cyclone moves southeast into western OR Friday
night/early Saturday morning.  There is a good QPF consensus among
the models out west. WPC QPF was based strongly on the previous
WPC forecast since it was close to the most recent model guidance.

Roth/Burke