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WPC Met Watch

 
Mesoscale Precipitation Discussion: #0989 (2018)
(Issued at 944 AM EDT Tue Oct 16 2018 )

MPD Selection
 


Graphic for MPD #0989

Mesoscale Precipitation Discussion 0989
NWS Weather Prediction Center College Park MD
944 AM EDT Tue Oct 16 2018

Areas affected...Portions of Acadiana in LA

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

Valid 161343Z - 161643Z

Summary...Convection continues to fester near an area where 3-7"
of rain fell overnight.  Hourly rain totals to 2.5" with an
additional local 5" is possible over the next several hours.

Discussion...A stationary front has been the focus for persistent
thunderstorm activity which was previously part of a band but has
now degenerated into an organized cluster over Vermilion Parish. 
Inflow at 850 hPa is convergent out of the south at 20-30 kts per
VAD wind profiles, with effective bulk shear of similar magnitude.
 Precipitable water values of 2-2.25" lie here per recent GPS
data.  Broad divergence is seen over the region east of shortwaves
across central TX and near the TX/OK border.

The mesoscale guidance has not been handling this activity well,
though it generally has gotten the idea of convection with heavy
rainfall becoming smaller in scale.  While RAP guidance indicates
a loss of low-level inflow in the near future, GFS guidance
indicates that effective bulk shear of 20-30 kts should be
available to help organize storms in this area.  ML CAPE values
are expected to increase due to daytime heating southeast of the
boundary, which should continue to allow it to be an effective
focus for organized convection.  A slight amount of backing to the
low level flow might shift the boundary a little more westward
with time.  The parameters suggest that hourly rain totals to 2.5"
and local amounts to 5" remain possible for another several hours.
 As soil conditions should be saturated, either due to recent
rains or in wetlands within this area, flash flooding is a concern
primarily within urbanized areas.

Roth

ATTN...WFO...LCH...LIX...

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

LAT...LON   30339232 30279152 29809188 29539226 29649279
            29859272


Last Updated: 944 AM EDT Tue Oct 16 2018
 

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