720
AWUS01 KWNH 180159
FFGMPD
SDZ000-NDZ000-180730-

Mesoscale Precipitation Discussion 0457
NWS Weather Prediction Center College Park MD
958 PM EDT Mon Jun 17 2024

Areas affected...northern South Dakota, central/eastern North
Dakota

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

Valid 180157Z - 180730Z

Summary...Showers and thunderstorms moving across western ND will
expand in coverage to the east while intensifying tonight.
Rainfall rates of 1-2"/hr are likely, which through training could
produce 2-4" of rain with locally higher amounts. Flash flooding
is possible.

Discussion...The regional radar mosaic this evening depicts
widespread showers moving out of western ND, and in the past 1-2
hours an intensification of reflectivity has been noted. This area
of precipitation is being driven by forcing ahead of a potent
shortwave embedded within an approaching trough axis, with height
falls and upper diffluence in the RRQ of a departing jet streak
contributing to the impressive synoptic ascent. At the same time a
stationary front is draped across ND, with an intense overlap of
PWs of 1.2-1.4 inches and MUCAPE nearing 1000 J/kg aligned south
of this boundary. Regional VWPs indicate the 850mb LLJ has begun
to intensify, reaching 40 kts from the SSW, which is impinging
favorably into the front for additional ascent, while also drawing
the more robust thermodynamics northward.

Activity is blossoming more rapidly than the high res CAMS
suggest, but the overall trend in the models is still supported.
During the next few hours, the 850mb LLJ is progged to reach an
incredible 50-60 kts across NE/SD, above the all-time max
climatological percentile according to NAEFS. This will surge
low-level moisture flux to above +5 sigma, resulting in an extreme
convergence of moisture transport vectors into eastern ND. With
increasing MUCAPE also occurring across that area, it is extremely
likely that convective coverage will expand and intensify, with
both the HREF and REFS probabilities suggesting a 50-70% chance of
rainfall rates reaching 1-2"/hr. Mean 0-6km winds will continue to
be elevated at 30-40 kts, but aligned Corfidi vectors to the
stationary front and the mean wind indicates that training is
expected, with some additional development S/SW into the greater
instability supporting even more prolonged training even as the
entire cluster pivots east. This could produce stripes of 2-4" of
rain with locally higher amounts.

7-day rainfall according to AHPS has been well below normal across
much of the area, although exceptions exist, especially in
northern ND, generally north of the front. Fortunately, the
heaviest rainfall footprint from the CAMS, which is supported by
the ingredients, is generally expected to fall across drier soils
where FFG is 2-3"/3hrs. The intensity of the rainfall could still
produce rapid runoff across these areas however, so instances of
flash flooding are possible.


Weiss

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

ATTN...WFO...ABR...BIS...FGF...UNR...

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

LAT...LON   48369853 48349741 48119717 47559696 46799704
            46389769 45599978 45240059 44900132 44730195
            44930247 46720156 47800038