509
AWUS01 KWNH 141455
FFGMPD
MNZ000-SDZ000-NDZ000-142045-

Mesoscale Precipitation Discussion 0882...Corrected
NWS Weather Prediction Center College Park MD
1054 AM EDT Wed Aug 14 2024

Corrected for Concerning tag to Flash Flooding Likely

Areas affected...North Dakota...Ext Northern South Dakota...

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

Valid 141450Z - 142045Z

SUMMARY...Strong dynamics/moisture flux into confluence zone
should support heavy rain rates and localized totals of 3-5" are
possible resulting in possible flash flooding through late
afternoon.

DISCUSSION...GOES-E WV suite depicts the leading
shortwave/height-falls of broad large scale Pacific Northwest
trough is starting to press eastward across the Northern High
Plains, with NNW to SSE ridge axis across northern NDAK back
through the Lower Missouri River Valley where embedded
MCV/southern stream shortwaves are moving through with the most
potent crossing out of NEB into SW MN at this time.  The polar
stream shortwave appears to be negatively tilted across WY with a
favorable south to north right entrance 60kt jet entrance across E
ND at this time.  The combination of strong dPVA and divergence
aloft is spurring deepening sfc to 850 mb low along/north of the
Black Hills, while backing low level flow and effective warm
conveyor belt into eastern SD and to central ND.  20-30kts of
850mb LLJ continues to flux increasing moisture aloft with values
of 1.5 total PWat, increasing to 1.75" over the next few hours.

The orientation of the pattern is also strengthening
FGEN/confluence along and downstream of the 850mb through central
ND as westerly flow impinges and strengthening convergence, flux
of the amplified moisture will overcome more limited
instability/lapse rates (1000-1250 J/kg MUCAPE) to generate
stronger thunderstorms with enhanced rainfall over the next
3-6hrs.   Already a few clusters have developed along and west of
the boundary in SW ND and along the boundary exiting Perkins, SD
into Grant county, ND.  Given strength of height-falls/dPVA, cells
will move northward along the boundary with reducing forward
propagation vectors the further north going along the deformation
zone.  This should allow for back-building and favorable
training/merging profile for 3-4 hrs.  Rates of 1.5"/hr
occasionally reaching 2"/hr, seem probable to induce a spot or two
of 3-5" totals along the line likely resulting in localized flash
flooding into early evening, confidence is enhanced by 3"/6hr
probability from the 06z HREF of 45-50% with a spot of 20% of 5".
While 12z HREF is still coming in, the 12z components still
continue to further support this potential if a shade further
north than the 06z signal.

Downstream across E ND, NE SD; warm advection in the q-axis
suggests moderate rainfall with perhaps an embedded convective
element may increase rainfall totals to be at or just below lower
FFG values in the area.  As such, the area is incorporated into
this MPD, as there is a non-zero potential (therefore lower
confidence) of FFG exceedance resulting in a possible incident of
low-end flash flooding as well.

Gallina

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

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

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

LAT...LON   49140116 48939935 47689882 46339696 45579656
            45229704 45319817 45769944 45590123 46220261
            46630387 48010383 48770276