Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
155 PM EDT Sat Apr 28 2018


Prelim Day 1 QPF Discussion
Valid Apr 29/0000 UTC thru Apr 30/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1


...Northeast...

The mid to upper level trof moving through the Great Lakes region
this afternoon will continue to strengthen into a well defined
closed low moving from the eastern Great Lakes across the northern
Mid-Atlantic tonight and into eastern NY/western New England
during the day on Sunday.  Large scale lift will strengthen to the
north of this amplifying closed low---supporting an increasingly
well defined comma head/deformation precipitation region affecting
northern NY state into northwestern New England.  Model consensus
is for moderate to locally heavy precip totals across these
regions.  The lowering heights associated with the deepening mid
to upper low will support rains changing over to snow across the
Adirondacks late tonight into Sunday with generally light snowfall
accumulations expected,  Precipitation along the trailing cold
front forecast to sweep east off the Mid-Atlantic coast tonight
and through New England Sunday will be more progressive than the
comma head/deformation area---limiting precip totals to the light
to moderate side.

...Pacific Northwest---northern Great Basin into the Northern
Rockies...

The closed low along the Oregon coast this afternoon will be
moving inland tonight through the Pacific Northwest and into the
northern Great Basin-Northern Rockies region Sunday. Model
consensus for the greatest precip totals is to the north of this
closed low where comma head precip may pivot from just north of
the U.S./Canadian borer across southern B.C. into southwest
Alberta.  To the south of this---showery conditions will persist
through the Pacific Northwest---northern Great Basin into the
Northern Rockies.

...Central to Southern Rockies into the Southern High Plains...

A broadly upper difluent flow pattern will spread downstream of
the inland moving closed low across the northwest U.S. through the
Central to Southern Rockies and into the Southern High Plains. 
This will support widely scattered showers at the beginning of the
day 1 period over the Central to Southern Rockies and then again
Sunday afternoon farther east into the Southern High Plains along
the dry line/lee trof position.  Light to locally moderate precip
totals possible through the Central to Southern Rockies.   Hi-res
models are more emphatic about locally moderate to heavy precip
totals along the dry line/lee trof Sunday afternoon--although
confidence is low with placement.


Oravec