Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
1202 AM EST Tue Mar 06 2018


Prelim Day 1 QPF Discussion
Valid Mar 06/1200 UTC through Mar 07/1200 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...Northern Plains/Great Lakes/East/Gulf coast...
An occluded cyclone and its attendant frontal boundaries are
expected to spread precipitation, some of it wintry, across the
region.  The system should increasing amounts of precipitation
across the Mid-Atlantic States due to strengthening 650-850 hPa
frontogenesis across the region. In the wake of the system near
the Great Lakes, areas of the Upper Peninsula of Michigan should
see lake effect/enhanced precipitation as cyclonic flow
strengthens and slight cooling occurs at 850 hPa.  In general, the
guidance has trended slower across the Southeast when compared to
continuity, where the heaviest precipitation is expected due to
1.50"+ precipitable water values, instability near and offshore
the coast, and 30+ kt inflow at 850 hPa. 

To account for the above, used a 30/15/15/20/20 blend of WPC
continuity/the 02z National Blend of Models/00z NAM/12z ECMWF/00z
ARW with some 12z NSSL WRF thrown in early.  A little bit of the
00z UKMET was thrown in manually to further slow the evacuation of
rainfall across the Southeast.  Per coordination with our Winter
Weather Desk, went much more towards the National Blend of Model
output east of the Keeweenaw Peninsula of Michigan where the best
lake effect is anticipated.  The contributions of the ARW and NSSL
WRF were to better account for the Gulf coast convection since
they had a better handle on it than the other guidance,
particularly the 00z GFS, whose mass fields indicate that the
heavy rainfall in the FL panhandle should fall closer to the Gulf
Coast than its precipitation pattern suggests.  See the WPC Winter
Weather suite of products for more details on winter weather
impacts. 

Roth