Mesoscale Precipitation Discussion 0546
NWS Weather Prediction Center College Park MD
521 PM EDT Fri Jul 27 2018

Areas affected...Western KS...Southwest NEB...Eastern CO...

Concerning...Heavy rainfall...Flash flooding possible

Valid 272121Z - 280230Z

SUMMARY...Developing fast moving MCS with potential downstream
stationary cells capable of producing flash flooding

DISCUSSION...Goes-16 Vis imagery and regional RADAR mosaic depict
strong bowing convection moving out of SW Nebraska into NW Kansas
with new development expanding into E Colorado, responding to
shortwave feature in mildly diffluent northwesterly flow. 
Currently, cells are very progressive with fast southeasterly
propagation vectors (20-30kts) feeding into the instability axis. 
Cells will be building into the coincident instability and q-axis
that extends across NW Kansas to south central KS, this is
delineated well in a dense CU/TCU field where mid-60s Tds and
mid-80s Ts and strong lapse rates support 2000+ J/kg MLCAPEs.

Sfc flow is increasing with southerly winds to 15kts that are also
generally confluent from Rush, KS to Red Willow, NE county.  This
slight increase in low level convergence has spurred convective
development in this axis in front of the main forcing bowing
lines.  These cells in Ellis/Graham/Norton counties are showing
signs of being stationary effectively waiting for the main forcing
upstream (locally back-building in the same spot).  This poses the
greatest risk for flash flooding in the short term, especially
given the lower FFG values in the axis (<1.5"/1hr or <2"/3hrs). 
Given TPWs are in the 1.5" range and modest surface flux, rates
over 1.5"/hr are supported and locally greater than 2" are
possible leading to the flash flooding risk.

With time, the LLJ is expected to strengthen to 20kts just after
00z increasing flux convergence and upscale growth into a larger
MCS.  While 500-1000mb thickness is very tight, suggesting
continued fast south-southeastward propagation, the eastern side
where flow/propagation vectors are lessened may support a bit
longer duration.  

Gallina

ATTN...WFO...DDC...GID...GLD...ICT...LBF...

ATTN...RFC...ABRFC...MBRFC...

LAT...LON   40620154 40550026 39909893 38859845 38109879
            37900087 39150210 40050234