581
AWUS01 KWNH 072309
FFGMPD
MOZ000-IAZ000-KSZ000-NEZ000-080500-

Mesoscale Precipitation Discussion 0405
NWS Weather Prediction Center College Park MD
708 PM EDT Fri Jun 07 2024

Areas affected...South-Central Nebraska through northeast Kansas

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

Valid 072308Z - 080500Z

Summary...Thunderstorms, including supercells, are expected to
increase in coverage and coalesce into an MCS into this evening.
Rainfall rates of 2-3"/hr will accompany the strongest convection,
which could result in 2-4" of rainfall with locally higher
amounts. Flash flooding is possible.

Discussion...The GOES-E IR satellite imagery this evening is
showing clusters of rapidly cooling cloud tops to nearly -70C
associated with supercells moving across central NE. This
convection is blossoming in response to ascent produced via a
shortwave rotating E/SE through the mid-level flow impinging upon
low-level convergence along a stationary front analyzed by WPC.
South of this boundary, the environment is extremely favorable for
heavy-rain producing thunderstorms characterized by a plume of PWs
around 1.7 inches over KS, near the daily record according to the
SPC sounding climatology, overlapping MLCAPE of 1500-2500 J/kg.
There is also pronounced bulk shear noted via the SPC RAP of 50-65
kts, which has supported supercells near the Sand Hills of NE,
within which MRMS rainfall has been measured at 2.5-3" within 1
hour.

As the evening progresses, it is likely these cells over NE, as
well as some developing in northern KS, will continue to expand
southeast and merge into a more broad cluster or MCS. This is
supported by a pronounced instability gradient aligned NW to SE
which should support the southeast motion of thunderstorms, which
will be enhanced by an increasingly robust LLJ out of the S/SW.
The intensifying LLJ will not only tighten the instability
gradient, but should also resupply moisture downstream of
expanding convection, with SREF 850-700mb moisture flux progged to
exceed 2.5 sigma this evening as the LLJ peaks around 40 kts.

The high-res CAMs are struggling to match the current radar
initialization, but despite that, they are all in agreement that
thunderstorms should expand and congeal within the robust
thermodynamics and impressive bulk shear. Rainfall rates within
thunderstorms could exceed 3"/hr at times as reflected by the
15-min HRRR precip accumulation fields, and 20-25% chance of 2"/hr
rates noted in the HREF. Although elevated mean winds and some
forward propagation may limit the duration of these rates, short
term training is possible embedded within the clusters, and the
HREF neighborhood probabilities indicate a 20-30% chance of at
least 3", and 10-15% for 5", focused near the KS/NE border.

0-10cm RSM from NASA SPoRT is modest across NE/KS, but is locally
higher due to 7-day rainfall of 100-150% in southeast NE and
northeast KS. This is where the FFG is relatively compromised, and
HREF exceedance probabilities for 3-hr FFG is as high as 20-30%.
This further reflects the increasing risk for isolated to
scattered flash flooding through this evening.

Weiss

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

ATTN...WFO...DDC...EAX...GID...GLD...ICT...LBF...OAX...TOP...

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

LAT...LON   41920045 41819886 41529733 40839543 39799473
            38609519 38349694 38469812 38979930 39950004
            41050069