AWUS01 KWNH 181038
FFGMPD
MOZ000-IAZ000-KSZ000-NEZ000-181530-

Mesoscale Precipitation Discussion 1084
NWS Weather Prediction Center College Park MD
637 AM EDT Tue Aug 18 2026

Areas affected...Southeast Nebraska...Southwest Iowa...Far
Northwest Missouri...Ext Northeast Kansas...

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

Valid 181035Z - 181530Z

SUMMARY...Short-term window for repeating elevated thunderstorms
in the wake of dying MCS/Bow echo. Rates of 1.75-2"/hr for 1-2+
hours suggest a stripe of 2.5-3.5" is possible and may result in a
spot or two of flash flooding conditions.

DISCUSSION...Regional RADAR denotes a decaying MCS/bow echo across
SW IA into N MO with well defined shortwave while a few bands of
elevated convection are developing WNW to ESE along the
rear-inflow jet for a loose "Bow & Arrow" appearance. Steepened
WNW to ESE isentropic boundary from older outflow and flanking
line is now ideally oriented for strong orthogonal convergence at
850mb with slowly veering LLJ in WAA regime. The LLJ is per KUEX
remains above 30-35kts and resides along the surface to 850mb
q-axis with mid to upper 60s sfc Tds noted across central KS to
south-central NEB. CIRA LPW shows core of 700-500mb moisture
aligning with slightly elevated values through the lower two
layers (sfc-850, 850-700mb) resulting in the enhanced overall
available moisture for TPW at or just above 1.75" for the core.
Mid-level cooling aloft is helping to steepen lapse rates for an
elevated upwind axis of MUCAPE along and west of the upwind edge
of the developing convective line(s), suggesting a bit more
back-building is possible over the next few hours. Given 2000+
J/kg of MUCAPE, updraft intensity to help inflow/flux convergence
should support 1.75-2"/hr rates. A secondary 800-700mb band is
also developing along the far northeast edge of the deep layer
convergence and northern edge of the instability/moisture
graident. While likely a bit less, the orientation is also
slightly favorable for repeating.

Obviously, in a 'Bow & Arrow' complex, the mean steering flow
above 700mb is parallel to the ascent plane and will help to
support repeating/training convection. Hi-Res CAMs are persistent
in earlier veering of the low-level flow and weakening expected
through the next 2-3hrs, but this is also a typical bias that
doesn't often pan out and the balance caused by the LLJ and
steeper outflow influenced isentropic surface especially as
instability remains in the upwind convergence zone. As such,
expect a stripe of enhanced repeating/training to result in
2.5-3.5" totals across central to southeast NEB through the early
morning. Recent rainfall has reduced FFG values across the area
with 1hr FFG less than 2" for most areas and less than 2.5"/3hrs.
MRMS Flash unit stream flow already suggests a solid stripe of
200-400 cfs/sqmi through Valley and S Greely heading toward NW
Merrick county. As such, localized exceedance is possible
suggesting localized flash flooding incident(s) are possible too.


Gallina

ATTN...WFO...DMX...EAX...GID...OAX...TOP...

ATTN...RFC...KRF...NWC...

LAT...LON 42069773 42009624 41429506 40719433 39959454
39759504 39799597 40079725 40469845 40919913
41479905 41609811

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