Flash Flood Guidance
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AWUS01 KWNH 220446

Mesoscale Precipitation Discussion 0272
NWS Weather Prediction Center College Park MD
1246 AM EDT Wed May 22 2019

Areas affected...southern/eastern AR into the MS Valley

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

Valid 220445Z - 221015Z

SUMMARY...A narrow axis of training and repeating convection is
expected to become better established across portions of
southern/eastern AR into the neighboring MS Valley. 3 hour
rainfall rates of 2-3 inches are possible which may lead to flash

DISCUSSION...04Z regional radar imagery showed a 50 mile wide axis
of convection extending from south-central AR, across the Missouri
Bootheel and into central IL. Weaker attempts at convection were
noted farther southwest toward the northern TX/LA border. The
southern end of the convective axis was elevated with the surface
based outflow boundary analyzed between CIR and PAH, down the MS
River to the east-central AR/LA border as of 04Z. Convection
across AR appears to be focused within an axis of 925-850 mb
convergence with mean-layer steering flow toward the northeast,
roughly parallel to the low level convergence axis. MLCAPE was
estimated to range between 500-1500 J/kg along the AR/LA border
within the source region for convective initiation, while MUCAPE
was between 500-1000 J/kg where the storms were occurring
according to area 00Z soundings and the latest SPC mesoanalysis.

As a powerful closed low over eastern NE continues northward
overnight, subtle low-mid level height rises across the middle and
lower MS Valley are expected to be accompanied by a northward
shift to the surface based outflow boundary across the AR/LA
border, with increasing MLCAPE to the north through 10Z. While the
degree of low level convergence is not expected to change over the
next 3-6 hours, better access to MLCAPE may boost convective
intensity and rainfall rates at times, leading to rainfall rates
of 1-2 in/hr with training and/or repeating cells at times. This
may lead to flash flooding, especially across northern locations
closer to the Missouri Bootheel where 3-hour Flash Flood Guidance
is only 2 to 2.5 inches.


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



LAT...LON   37228926 36588930 35069039 33999138 33139234
            33089317 33529352 34259319 35219224 36539082

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