Graphic for MPD #0674

Mesoscale Precipitation Discussion 0674
NWS Weather Prediction Center College Park MD
758 AM EDT Thu Aug 16 2018

Areas affected...Northeast AR, far southeast MO, western TN

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

Valid 161157Z - 161757Z

Summary...A localized flash flood threat continues through the
morning across across far northeast Arkansas, far southeast
Missouri, and far western Tennessee.

Discussion...Recent radar and IR imagery shows continued
convective development near the border of Arkansas, Missouri, and
Tennessee. This activity is developing just ahead of a shortwave
trough axis visible as mid level drying on WV imagery. Synoptic
ascent ahead of this feature is overlapping confluent 850mb flow
resulting in the maintenance of convective activity. 850mb
moisture transport is quite strong, with ~30kts of southwesterly
850mb flow pointed into the area. This wind is equal to, or even
greater, than the mean layer winds, supportive of continued
backbuilding of convection on the western edge of the activity.

Dual Pol and MRMS estimates as much as 5-7" of rain has fallen
over a narrow portion of far northeast Arkansas. This is
indicative of the type of localized totals the setup has the
potential to produce, and is similar to what occurred on small
scales the past few days across portions of TX,OK,KS,AR. The
overall setup appears to favor a persistence of small scale
training through the morning hours, with the axis shifting a bit
south and east of where it has been earlier this morning. Cloud
tops show continued pulses of cooling, although no large scale
upgrowth is seen. Thus an expansion of the heavier rainfall rates
appears unlikely, but a continuation of the smaller scale
localized intense rates is likely. Recent HRRR runs and the 06z
HREF are in good agreement on some 3"+ additional amounts over
western Tennessee, although both of these models may be a bit too
far northeast with their QPF.

Given that the heaviest rain is moving into areas that have drier
antecedent conditions, and the scale of intense rates is expected
to be small, will keep the MPD category as Possible...with
additional flash flood issues expected to be rather localized in
nature (although still potentially significant on a small scale).

Chenard

ATTN...WFO...MEG...PAH...

ATTN...RFC...LMRFC...

LAT...LON   36428934 36288887 35898846 35418836 35048851
            34948941 34978996 35289035 35599052 35949073
            36169077 36279041 36319004 36408970


Last Updated: 758 AM EDT Thu Aug 16 2018