Mesoscale Precipitation Discussion 0743
NWS Weather Prediction Center College Park MD
717 PM EDT Sat Sep 01 2018

Areas affected...north-central KS into southeastern NE and IA

Concerning...Heavy rainfall...Flash flooding likely

Valid 012316Z - 020515Z

Summary...The threat for flash flooding should increase overnight
from north-central KS/southeastern NE into IA. Rainfall of 3-5
inches will be possible in a couple of locations, some of which
may overlap with wet antecedent conditions over IA.

Discussion...Regional radar imagery from 23Z showed an ongoing
cluster of thunderstorms in north-central KS, north of I-70, in
Osborne and Russell counties, with a related cold pool just south
of the ongoing rainfall. KUEX one hour rainfall estimates were 1-2
in/hr but some hail contamination was likely inflating those
estimates a bit. VAD wind plots of 850 mb winds at KDDC and KICT
were near 20 kt from the south, with speeds forecast to increase
by the RAP to 35 kt by 03Z, pointed directly into the existing
outflow boundary which bisected I-70 at 23Z. This increase should
occur with typical nocturnal strengthening of the low level jet in
combination with an approaching 700-500 mb shortwave currently
moving across the central to southern High Plains. Forcing for
ascent ahead of this feature, increasing divergence aloft within
the right entrance region of a strengthening 250 mb jet axis from
NE into the upper MS valley, along with the increasing low level
moisture transport through KS should help to support the continual
regeneration of thunderstorms and training from north-central KS,
eventually spreading and expanding east-northeastward into
southeastern NE and central IA.

Portions of IA received 3-6 inches of rain over the past 24 hours
which has allowed for Flash Flood Guidance (FFG) values to lower
to 1-2 inches in 3 hours. Ample CAPE (2000+ J/kg) is already in
place to the south of a remnant outflow boundary in IA and over
southern and eastern KS (via the SPC mesoanalysis) to help sustain
convection well into the night. Given increasing precipitable
water values into the 1.75-2.00+ inch range across the region,
parameters will be present to allow for 1-2 in/hr rainfall rates
and repeating heavy rains. Flash flooding appears likely through
at least 05Z.

Otto

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

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

LAT...LON   42369282 42219202 41889163 41399166 41059189
            40829220 40729272 40709364 40619461 40269607
            39799695 38769859 38519963 38540021 38820065
            40030070 40600009 41029911 41629763 41929625
            42249494 42339400