Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
229 PM EDT Sun Apr 08 2018


Prelim Day 1 QPF Discussion
Valid Apr 09/0000 UTC thru Apr 10/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...Florida and eastern Carolinas and Georgia...

A frontal boundary stalls across central FL, before moving back
north as a warm front tonight into Monday. Moisture and
instability focused on the front feed convection that produces
locally heavy rainfall, both this afternoon in south central FL
and Monday afternoon in northern FL.
There was enough model agreement to use a multi model blend as a
basis for the WPC QPF.

This combination placed an axis of 0.50 to 1.00 inches of qpf from
Lake Okeechobee to Vero Beach and West Palm Beach this afternoon
and again over northeast FL Monday afternoon. Locally higher
amounts are possible if training occurs along the the front. 
Three hour flash flood guidance values are fairly high, so while
locally heavy rainfall is possible, flash flooding is not expected.

On Monday a ripple of low pressure develop along the front and
moves off the southeast coast.
The 12z and a few of the high res ARW/ARW2 runs show higher
amounts further west onshore in the eastern Carolinas, although
the gfs/ecmwf/Canadian regional GEM do not have higher amounts
onshore.
The latter cluster was given a little more weight given they agree
best with the predominant cyclone track.

...Pacific Northwest/Rockies...

The upper level wave across the northern Rockies this evening
moves quickly southeast across Wyoming and CO with an upper jet
streak progressing across ID/UT and CO, providing favorable upper
divergence maxima crossing the ranges of western MT/western WY and
northern CO.  Precip streaks out on to the Plains of CO in tandem
with the upper divergence maxima late tonight/early Monday.

Rainfall rates taper in the Pacific northwest as a mid-upper level
Pacific ridge develops and drifts east towards the region.  The
ridge has the net effect of reducing the strength of onshore flow
and even backing of the south towards the south occurs Mon in
WA/OR.  With the weakening lift and convergence, coverage should
steadily diminish late tonight into Monday in the northwest and
northern Rockies.

There was generally good model agreement,so the WPC QPF used
continuity with a multi-model/HREF Mean blend.

...Mid MS Valley/OH Valley/central Appalachians...

Recent radar/surface observations show widespread precip across
the mid MS Valley to central Plains as coupled low level
convergence and upper divergence combined with low level moisture
fluxes to produce the precip.  The models still forecast to
low-mid level trough and sfc low to weaken, so the strength of low
level convergence weakens and precip coverage amounts start to
wane.
The moisture in the vicinity of the low level warm front moves out
of KY into the WV/VA Appalachians tonight into early Monday.
Enhancement are expected in windward terrain in these areas.  See
the winter weather graphics and discussion for potential snow
amounts.

Petersen