Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
937 AM EDT Wed Jun 06 2018


...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL PLAINS...

...Southern Nebraska south into Kansas and northern Oklahoma...

The models do cluster well with the development and track of the
mesoscale/convectively-aided vort max along/south of the 582 dm
500 mb height -- over the central High Plains this evening and
straddling the NE-KS border overnight. The model trends,
especially the CAMs, indicate the convection growing upscale this
evening downwind of this MCV.
The cells then propagate farther south of the surface frontal
boundary (i.e. into KS and perhaps far northern OK)
due to the robust deep-layer instability (MUCAPES above 3500 j/kg
per the GFS/ECMWF), owing to the steep mid level lapse rates (over
8 C/KM).  Lift is provided by the 06z NAM combination of 700 mb
theta-e advection and convergence, with favorable southerly LLJ
increasing overnight.  Convection develops into the inflow axis
with uncertainty
regarding how quickly the mid level cap weakens further south as
you cross KS into OK. Both propagation into the inflow and
development along outflow boundaries will allow the MCS and
additional convection along outflows to reach across southern KS
and possibly into northern OK, as indicated by the NSSL WRF.

Considering the degree of instability as the convection continues
to organize/grow upscale later this evening short term (1-2
hourly) rainfall rates could exceed FFG underneath the strongest
cells, especially over southern NE and central KS given the lower
FFG (1.5"/hour). The GFS indicates 2-3 inches of rain, as well as
the 00z WRF ARW, with an isolated 4 inches from the ARW.  The 06z
Canadian regional GEM shows 4-6 inches in north central KS. 5 of
the 13 SREF ARW members have 3 or more inches of rain ending 12z
Thu in south central NE. 

Petersen