Mesoscale Precipitation Discussion 0203
NWS Weather Prediction Center College Park MD
532 AM EDT Sat May 14 2022

Areas affected...Western Arkansas... Ext Eastern Oklahoma...

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

Valid 140930Z - 141200Z

SUMMARY...Slow to stationary convection with ample moisture pose
highly localized but potentially considerable flash flooding.

DISCUSSION...Recent RADAR and GOES-E 10.3um EIR loop depict a few
thunderstorms developing along the OK/AR border with one
particularly strong cell in Sebastian county, AR with observations
of 1.5-2" in the last hour or so.   VWP and RAP analysis denote a
weak but sufficient 15-25kt 85H westerly flow upgliding over weak
surface easterly flow.  RAP analysis also denotes weakening CINH
values below 25 J/kg though the OK/AR border resides in an
instability axis with 2000-2500 J/kg of MLCAPE from NE OK into W
AR.  CIRA LPW and Sfc Tds indicate a solid moist and unstable
environment with PW values totaling around 1.5" available for
these thunderstorms that have developed.

Above 85H the winds slacken between flow regimes which suggests
15-20kts of easterly cell motions though combined with upstream
backbuilding resulting in near zero overall propagation vectors
suggesting continued stationary redevelopment but ample inflow to
maintain thunderstorms.  As such, continued very slow/stationary
cells are expected to expand in coverage. Hi-Res CAMs are poor at
handling such weak forcing mechanisms and placement of older
boundaries; however, there is a general agreement of a favorable
wave aloft to support a divergent pattern for a few hours to help
maintain favorable convective environment.   As such, 1.5-2"/hr
and 1-3 hour durations could spell localized totals in excess of
4" and result in flash flooding and if maintained too long, could
result in a considerable flooding event to unfold, but confidence
is low given such weak flow. 

Gallina

ATTN...WFO...LZK...TSA...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON   36279451 36239399 35919362 35609337 34719316
            34409376 34479411 34899449 35359461 35749467
            36089468