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WPC Met Watch

Mesoscale Precipitation Discussion: #0044
(Issued at 1018 AM EST Mon Feb 10 2020 )

MPD Selection

Graphic for MPD #0044

Mesoscale Precipitation Discussion 0044
NWS Weather Prediction Center College Park MD
1018 AM EST Mon Feb 10 2020

Areas affected...Deep South

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

Valid 101517Z - 102117Z

Summary...A broken band of training showers and thunderstorms is
expected to drop hourly rain amounts up to 2" with local amounts
in the 3-5" range.  These amounts should lead to instances of
flash flooding over the next several hours.

Discussion...A wave of low pressure near the ArkLaTex along with a
weak warm front across the Lower Mississippi Valley are acting as
the foci for overrunning showers and thunderstorms with slowly
increasing rainfall amounts; CIN is forcing a good amount of the
convection to be elevated over the warm front.  MU CAPE of
500-1500 J/kg exists across LA, southern AR, and MS per SPC
mesoanalyses.  Inflow at 850 hPa is convergent out of the
southwest at 30-50 kts per VAD wind profiles.  The mean 850-400
hPa wind is out of the west-southwest at similar magnitude, with
the 1000-500 hPa thickness lines beginning to align with the mean
flow.  Precipitable water values in the area are 1.3-1.7" per GPS
data.  Storms with some structure (an occasional mesocyclone)
along with a general increase in cell coverage have led to some
increase in the hourly totals across LA and MS per WSR-88D
imagery, with local hourly amounts of 1"+ in several spots and 2"
east of Olla, LA.

The expectation is for the warm front to shift eastward with time
which would allow rainfall is areas farther east in eastern MS and
AL to become more convective as MUCAPE/MLCAPE increase.  GFS-based
Galvez-Davison Index values imply slowly increasing convective
coverage with time today across this region.  Slowly veering 850
hPa flow will become more aligned with the mean flow, which also
would increase the potential for heavy rainfall.  But, the axis of
850 hPa convergence is expected to shift somewhat, which should
limit rainfall magnitude.  Hourly totals of 1-2" are expected
where thunderstorms happen to train within this quick flow
pattern, with the 06z HREF probabilities of 1"+ highest through
18z before slowly fading thereafter.  While a bulk of the
mesoscale guidance forecasts local amounts of 2-4" in this region,
the 00z WRF NSSL (5") and the 12z NAM CONEST (7") indicating
higher potential.  Think local amounts in the 3-5" range are
possible here.  Two week and one month precipitation anomalies are
generally 1-2 times average, leading to soils which are partially
saturated which is reflected in the flash flood guidance values. 
Flash flooding is considered likely.




LAT...LON   34168775 33498548 32188793 31509239 31639407
            31819463 32139442 32689381 33289205

Last Updated: 1018 AM EST Mon Feb 10 2020

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Page last modified: Wednesday, 13-May-2015 19:29:02 GMT