670
AWUS01 KWNH 170559
FFGMPD
MNZ000-IAZ000-NEZ000-SDZ000-171030-

Mesoscale Precipitation Discussion 0450
NWS Weather Prediction Center College Park MD
159 AM EDT Mon Jun 17 2024

Areas affected...northeastern NE into southeastern SD,
northwestern IA and southwestern MN

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

Valid 170558Z - 171030Z

Summary...Training of thunderstorms is likely to produce areas of
flash flooding from near/north of the eastern SD/NE border into
southwestern MN and northwestern IA through 10Z. 1 to 2+ in/hr
rainfall rates are expected along with additional totals of at
least 2 to 4 inches.

Discussion...A WSW to ENE axis of thunderstorms was observed on
regional radar imagery at 0530Z from the central NE/SD border into
southeastern SD. MRMS-derived peak hourly rainfall has been in the
2.0 to 2.5 inch range over southern Tripp and Gregory counties in
southern SD over the past 2 hours with 3-hr estimates of 4 to 5+
inches as steering flow oriented parallel to the thunderstorm axis
has allowed for training. The thunderstorm axis was elevated to
the north of a slow moving front that extended SW to NE from
southwestern NE into southern MN at 05Z, located at the nose of
stronger 850-700 mb winds averaging 30-50 kt from the south. SPC
mesoanalysis data from 05Z showed the elevated convergence axis
and thunderstorms along a CAPE gradient containing 1000-2500 J/kg
MUCAPE. Aloft, lift was being enhanced by placement within the
right-entrance region of a 100 kt jet near 200 mb (sampled by GOES
East DMVs).

The strong elevated convergence axis is expected to translate ENE
along the elevated frontal boundary, reaching southwestern MN by
10Z out ahead of an advancing 700-500 mb shortwave currently over
the central High Plains. The axis of low level forcing should lift
north gradually as the surface front edges north later this
morning but some southward propagation of convection will be
possible into the inflow. The RAP is forecasting the upper level
jet max to strengthen through 12Z, reaching 120 kt by 12Z from
eastern ND into northern MN, allowing a region of strong
divergence and diffluence to set up over the Missouri and Big
Sioux River Valleys. While mean steering flow is not forecast to
perfectly align with the axis of convergence throughout the next 4
hours, there will likely continue to be areas of training from WSW
to ENE with rainfall rates of at least 1-2 in/hr. Additional
rainfall totals of at least 2 to 4 inches are expected for
portions of the eastern SD/NE border into southwestern
MN/northwestern IA as the flash flood threats expands through the
overnight.

Otto

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

ATTN...WFO...ABR...DMX...FSD...LBF...MPX...OAX...UNR...

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

LAT...LON   44579428 44159356 43359377 42599492 42229721
            42669864 42680014 42920086 43470055 44289693