Quantitative Precipitation Forecast Discussion
NWS Weather Prediction Center College Park MD
253 PM EDT Sat Mar 31 2018


Prelim Day 1 QPF Discussion
Valid Apr 01/0000 UTC thru Apr 02/0000 UTC
Reference AWIPS Graphics under...Precip Accum - 24hr


Day 1

...Southern Plains into the Lower MS Valley and TN/OH Valley...

Showers and embedded thunderstorms will continue to build south
along the cold front into much of central and northern AR into
eastern OK and far northeast TX. Would expect to see coverage
increase by 0z as low level convergence along the front increases.
Based on the 12z set of high res models, WPC did trend higher with
QPF amounts from far northeast TX northeast into western KY. The
consensus is for a broad swath of 0.5"+, with amounts locally as
high as 1-2". From northern AR into Ky instability is pretty
meager...thus while the duration of showers here may be a bit
longer than further south...rates should generally not be high
enough to promote much of a flash flood threat. Further to the
southwest...from far northeast TX into western AR...instability is
higher...but even here it is progged to remain under 1000 J/KG.
With the slightly better instability...rainfall rates should be
locally higher here...although in general storms are expected to
remain pretty progressive...limiting any flooding threat. This is
supported by the 12Z HREF...which shows high probabilities of
exceeding 1"...but only very low chances of isolated 2" amounts.
The fact that some of these areas have been anomalously wet as of
late suggests the flash flooding threat is non zero in any more
susceptible locations...however think the threat remains below 5%
and thus will continue with no marginal risk area. WPC QPF across
this area leaned towards the 12z high res runs...with more
weighting given to the ARW and ARW2 which appeared to show a more
realistic evolution of convection.


...Lee of the Central Rockies into the Central Plains...

A wave ejecting east out of the Rockies will support increasing
isentropic lift ahead of it...with decent mid level frontogenesis
also noted. Thus should see a band of locally heavy snow from
southeast WY southeast across NE. Overall models are in pretty
good agreement (better agreement than the band early this morning
over the NP/Upper MS Valley)...although some minor north/south
axis differences remain. WPC QPF ends up closest to the 12z HREF
blended mean...which seemed like a good middle ground solution.

...Northwest...

Showers will return to the Pacific Northwest during the day Sunday
as a good amount of mid/upper level energy drops southeast into
the area. For the day 1 period models have trended wetter on
recent runs...and thus WPC went in this direction as well. Given
the relatively good agreement seen...a multi model blend was used.

Chenard