Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
301 AM EDT Sat May 05 2018


Prelim Day 1 QPF Discussion
Valid May 05/1200 UTC thru May 06/1200 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

TN Valley into the Central Appalachians

There is good model agreement with the evolution of the well
defined southern stream trof pushing into the Lower MS/Lower TN
Valley region Saturday---east northeastward through the OH Valley
and toward the Central Appalachians Saturday night into early
Sunday. Strongly difluent upper flow ahead of this trof in an axis
of above average pw values---1 to 1.5+ standard deviations above
the mean---will support widespread moderate to heavy precip totals
from the TN Valley northeastward into the Central Appalachians and
Mid-Atlantic.  Stream flow is initially near or slightly below
normal across these areas but is expected to rise quickly to much
above to high flow as per the national water model from hourly
rainfall rates of 1"+ as the area of organized precips spreads
east northeast across these areas.  No significant changes made to
the previous excessive rainfall potential outlook across these
regions with a marginal risk area stretching from north central TN
into eastern KY--much of WV into Southwest VA. Rain


Central to South Florida

The closed upper low moving into central Cuba is expected to
become nearly stationary day 1.  Higher pw values expected to
rotate west northwestward to the north of this closed low
increasing pw values to much above average values across much of
central to south Florida day 1.  The increasing pw values will
also be accompanied by increasing shower activity for central to
South Florida.  Low confidence on the details of qpf across these
areas with model consensus for moderate to locally heavy totals.

The anomalous pw values will also be drawn northward ahead of the
above mentioned upper trof pushing east northeast from the Lower
MS Valley---TN Valley into the Central Appalachians.  These
anomalous pw values will impact coastal areas from the upper coast
of SC---northeastward into eastern and coastal NC Saturday night
into early Sunday.   Heavy rains are possible in a region of
enhanced upper difluence in the right entrance region of an upper
jet over the Mid-Atlantic.  There is some spread with the exact
axis of the heaviest precip---with some models showing it just
along the coast of NC---especially across the Outer Banks---while
others are just offshore.  The day 1 qpf leaned toward the href
mean depicting the heaviest axis just offshore of the Outer Banks
but still having heavy precip affecting the Outer Banks.  No
changes planned to

Oravec