898
AWUS01 KWNH 181845
FFGMPD
WIZ000-MNZ000-SDZ000-NDZ000-190043-

Mesoscale Precipitation Discussion 0460
NWS Weather Prediction Center College Park MD
243 PM EDT Tue Jun 18 2024

Areas affected...Portions of the Upper Midwest

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

Valid 181843Z - 190043Z

SUMMARY...Redeveloping bands of heavy showers and thunderstorms
are expected through the afternoon and early evening hours. Some
training of this activity may result in runoff problems and
concerns for flash flooding.

DISCUSSION...Surface observations show a wave of low pressure over
northeast SD which will be lifting across west-central to
northeast MN this afternoon as an upper-level trough gradually
ejects east across the northern High Plains. A strong low-level
jet reaching 40 to 50+ kts out ahead of this low pressure system
will be interacting with a warm front across central to northeast
MN to drive a renewed threat of rather organized showers and
thunderstorms going through the afternoon and early evening hours.

In the wake of earlier convection, the latest visible satellite
imagery shows some clearing taking place over areas of central and
southern MN, and already the MLCAPE values have recovered to 2000
to 3000 J/kg. An additional uptick in instability is expected over
the next few hours with more diurnal heating, and with increasing
convergence along the warm front along with enhanced isentropic
ascent and frontogenetical forcing, there should be an uptick and
expansion of convection for areas along and north of the warm
front. Areas of central to northeast MN in particular will likely
see concerns for rather well-organized and locally training bands
of convection given this set-up and with convection aligned
parallel to the deeper layer steering flow.

However, as warm-sector boundary layer destabilization continues
in conjunction with relatively strong shear parameters, there will
eventually be the development of surface-based convection along
and just ahead of the approaching upstream cold front.

The 12Z HREF guidance supports rainfall rates that are quite high,
and capable of reaching 2.0 to 2.5 inches/hour. The latest
CIRA-ALPW data shows a pronounced area of enhanced moisture
concentrated in the 850/700mb layer with strong LVT magnitudes.
Therefore the stronger convective cells are expected to be quite
efficient in producing high rainfall rates.

Additional rainfall totals by 00Z (7pm CDT) this evening will be
capable of reaching 3 to 6 inches with much of this connected to
the training convection threat north of the warm front. However,
warm-sector areas of southern MN may also see locally as much as 2
to 4 inches of rain as convection here organizes later in the
afternoon ahead of the cold front.

Given the locally wet antecedent conditions and additional totals,
some runoff problems and concerns for flash flooding will exist.

Orrison

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

ATTN...WFO...ABR...DLH...FGF...FSD...MPX...

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

LAT...LON   48529091 47918980 46969050 46219132 45169218
            43659372 43619558 44129618 44949646 45619679
            46529665 47429552 48019423 48469287