Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
259 PM EDT Mon Apr 09 2018


Prelim Day 1 QPF Discussion
Valid Apr 10/0000 UTC thru Apr 11/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...North Florida...

The surface frontal boundary currently aligned west to east across
north Florida is not expected to move much during the upcoming day
1 time period...remaining parallel to the west southwest mid to
upper level flow.  With pw values expected to remain 2+ standard
deviations above the mean---favorable right entrance region jet
dynamics and mu-cape values 1000-2000+ j/kg along and to the south
of this front---heavy rain potential will persist through the
period.  Short term run to run continuity in the hi res guidance
is poor---leading to low confidence with the shorter term details
of the precip maxima.  However---there is overall higher
confidence with the heavy precip potential for the 24 hour period
given the strong model signal and overall favorable synoptic set
up.  No changes to the thinking for potential of isolated
excessive rainfall amounts in the vicinity of this front with no
changes made to the previous excessive rainfall potential outlook.
 With little overall movement to the front expected---training of
cells over the same area is possible.

...Coastal Southeast...

Shortwave energy moving east from the lower MS Valley into the
southeast will help expand precip to the north and northeast of
the potentially heavy axis in the vicinity of the west to east
oriented front over north Florida.  There is a fairly large spread
in amounts among the various guidance this cycle--leading to low
confidence.  WPC favored the somewhat lighter amounts of the HREF
mean over the heavier 0000 UTC ECMWF and 1200 UTC GFS.  The 1200
UTC ECMWF did trend lighter with precip across these
areas---closer to the favored HREF mean.

...Mid Atlantic--NY state into central to southern New England...

A separate---farther northern branch of shortwave energy is also
expected to push east day 1 from the lower Great Lakes into the
Mid Atlantic and into southern New England.  This will support a
farther north area of light to locally moderate precip values
across these areas.

...South Texas...northeast Mexico

The western extent of the surface front across north Florida will
be pushing slowly southward from far south TX into northeast
Mexico.  Models are indicating a fairly strong axis of convergence
into this boundary in an increasingly anomalous axis of pw
values...1.5 to 2+ standard deviations above the mean. This will
support increasing showers tonight into early Tuesday over far
south Texas/northeast Mexico before all activity pushes south into
northeast Texas late Tuesday morning into early afternoon.  Model
consensus is for the heaviest activity to the south of south TX
with heavy precipitation potential there and mostly moderate
totals over far south TX.

...Northern California---Pacific Northwest into the northern
Rockies...

The first in what will be a series of height falls over the next
few days to rotate through the base of the northeast Pacific trof
will push northeast and inland from northern California into the
Pacific Northwest.  An organized area of precip along and ahead of
the associated frontal boundary will accompany these height
falls---supporting generally moderate totals from Northern
California across the Pacific Northwest and into the northern
Rockies.

Oravec