924
AWUS01 KWNH 260150
FFGMPD
MOZ000-IAZ000-KSZ000-NEZ000-SDZ000-260700-

Mesoscale Precipitation Discussion 0497
NWS Weather Prediction Center College Park MD
946 PM EDT Tue Jun 25 2024

Areas affected...Eastern NEB...Southwest IA...Northwest
MO...Northeast KS...Far Southeast SDAK...

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

Valid 260145Z - 260700Z

SUMMARY...Slow moving, perhaps retrograding cells may merge before
consolidating into a larger complex picking up forward speed.
High moisture availability will allow for efficient rainfall
production with 2"/hr rates possible and spots of 2-4" across
saturated/flooded grounds likely to induce spotty flash flooding
conditions.

DISCUSSION...GOES-E Visible to SWIR 3.9um imagery depicted a milky
agitated area in/south of the frontal zone cross the Great Lakes
back acorss S IA and to a surface wave exists in central NEB.  A
broader mid-level trough/shortwave is dropping southwest out of
SDAK allowing for backed low to mid-level flow combined with full
solar heating on saturated grounds resulting in deep moisture up
to 2" angled back across the Missouri River Valley.  That heating
and high theta-E air continues to be very unstable with MLCAPE of
3500-4500 J/kg across the northern Sand Hills into SW IA.  Deep
layer convergence, likely responding to the weak DPVA/approaching
shortwave has trigger scattered destabilization and convective
activity over the last few hours.

Deep layer steering has been weak with 15-20kts of west to east
flow, but 500-1000 mb thickness pattern suggests continued
favorable back-building across NE NEB into NW IA allowing for
cells to take up slower motions/residency for localize intense
rainfall.  Rates of 1.5"/hr have been slowly up-ticking toward 2"
as cells moisten the small pockets of mid-level dry air in the
region.  Still spots of 2-4" are likely to occur across along and
north of the frontal zone in the MPD area of concern.   This is
also an area of significantly saturated ground conditions with
ongoing major river flooding, so any additional rainfall is likely
to induce localized flash flooding conditions or compound ongoing
flooding if falling near the middle range rivers/streams in the
area.

While there is some uncertainty, the overall coverage is expected
to continue and cells will likely merge and start to grow upscale
with greater DPVA/upper-level influences...combined with growing
cold pools.  As a complex develops into a potential bow, cells
will move past the 500-1000mb thickness ridge and combined with
cool pool acceleration will reduce duration with forward
propagation speeds.  However, this will result in stronger
moisture flux convergence along the leading edge and 2-3" totals
may occur in shorter duration as the complex moves south into N
MO.  This will move into areas of higher FFG and drier ground
conditions, so potential for flash flooding will reduce and focus
on sensitive urban settings, but still remain possible through the
overnight period.

Gallina

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

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

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

LAT...LON   43229871 43199746 42959606 42629476 42029358
            41449290 40669245 39579277 39069382 39159527
            40069689 40949761 42259869 42829908