632
AWUS01 KWNH 032341
FFGMPD
KSZ000-NEZ000-040400-

Mesoscale Precipitation Discussion 0549
NWS Weather Prediction Center College Park MD
741 PM EDT Wed Jul 03 2024

Areas affected...Southwest to south-central NEB...Northwest to
north-central KS...

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

Valid 032340Z - 040400Z

SUMMARY...Cell mergers and training/repeating may occur along
intersection of colliding convective lines across the nose of
enhanced moisture flux convergence.  Rates of 2"/hr and spots of
2-3" totals pose possible flash flooding conditions

DISCUSSION...Regional RADAR mosaic and GOES-Visible loop depict a
fairly rapidly moving squall line across the Sand Hills of
Nebraska, though the southwest flank is reducing in forward speed
at the southern edge of deeper mid to upper-level flow.  This is
orienting favorably for cores of the cells to repeat through the
South Platte Valley.  Additionally, downstream, an isolated cell
developed near the Lincoln/Frontier county line in an advanced
area of enhanced low to mid-level moisture.  Though there have
been a few left splits, the cell has remained stationary with
solid hail signature, though has some modest heavy rainfall core
building.  Fairly soon, the lines will merge and present an issue
for rapid 1.5-2" in sub-hourly duration to add to the 1-2" that
have fallen.

Additionally, the cell resided within a SE to NW nose of enhanced
moisture and untapped instability that remained west of the deeper
cloud cover in E KS.  Strengthening 15kt at surface and 25-30kts
at 850-700mb are backing to intersect orthogonal to the
approaching line.  This will allow for increased forward
propagation to the southeast, but will also increase moisture flux
convergence that should rapidly result in a quick burst of very
intense rainfall rates.  Totals of 1.5-2" should fall in less than
15-30 minutes with an additional .5-1" in the trailing moderate
shield and a swath of 2-3" totals may be possible over the next
few hours.

While current location in SW Nebraska has deep sandy soils that
could infiltrate much of that, the line will move further
southeast into less favorable infiltration and naturally lower FFG
values across north-central KS/south-central NEB; where 1hr FFG is
AoA 1.5" and 3hr are between 1.5-2.5".  As such, localized flash
flooding may become an issue in the next few hours.

Additionally, the line of scattered cells in E CO is tracking a
bit north of due east may also intersect the best
moisture/instability axis at a similar time as the southeast
propagating line.  Mergers with this line may further up-tick
short-term output further compounding localized flooding concerns
through the early overnight period.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...GID...GLD...LBF...

ATTN...RFC...MBRFC...NWC...

LAT...LON   41410000 40519845 40159809 39709814 39269861
            39170002 39480103 40210184 40930191 41170086