Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
236 PM EDT Sun Mar 18 2018


Prelim Day 1 QPF Discussion
Valid Mar 19/0000 UTC thru Mar 20/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...Central / Southern U.S...

A rather active Sat evening through Sun from the Central Plains to
parts of the South/Southeast into northern FL. Multiple streaks of
heavier rainfall is anticipated over the next 24 hrs, as a lead
subtropical short wave streams through the southern tier of the
country, only to be followed up by a dynamic southern stream
trough. The combination of the two features will produce
widespread qpf from KS to FL/GA.

The subtropical short wave has already produced clusters of
showers and storms across LA into MS and southern AL today. Rounds
of convective clusters should persist, as the short wave arrives
and moisture pools near a surface stationary front Sat evening
into perhaps the overnight hrs. The latest global models and
hi-res suite indicate the prime spot being southern GA/FL
panhandle where increasing instability is likely and possible
areal avg 1-2 inch amounts with locally higher values.

Meanwhile, a vigorous short wave, moving through the Four Corners
region today, will eject overnight into the central/southern
Plains. The guidance indicates broad swrly upper difluent flow
ahead of the negative tilt short wave for synoptic scale heavy
rains across eastern/central KS. This area of enhanced vertical
lift invof of the 500mb vort will progress downstream through
central/southern MO into the TN valley before tomorrow aftn and
possible active convection near the wedging frontal zone from the
TN Valley into AL/western GA.

Overall the guidance was very similar with mass fields and WPC
felt comfortable using a blend of 60% hi-res guidance, 20% global
models (GFS/ECMWF) and 20% NBM (National Blend of Models)


...Western U.S. Including the Central Rockies up through the
Dakotas...

Scattered areas of mainly light qpf is anticipated from the
Northwest through the northern Inter-Mountain west into the
northern Plains and Upper Midwest. Not much of an upper flow
regime with a closed low hovering just off the PacNW coast and
over the northern Plains, while an inverted trough extends from
the developing Plains cyclone into NE and the Dakotas. This is
where the most organized qpf is anticipated of up to a .50 inch,
some snow and rain mixed with snow. Overall WPC just followed a
blend of the latest model guidance.


Musher