Mesoscale Precipitation Discussion 0124
NWS Weather Prediction Center College Park MD
1109 PM EDT Sat Apr 13 2019

Areas affected...Northeast MS into northern AL

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

Valid 140310Z - 140710Z

Summary...Convection training along a line across northeast MS
into northern AL could pose a flash flood threat into the early
morning hours.

Discussion...Convection across MS/eastern LA is beginning to take
on a linear form, as the the west southwest mid level flow
increases ahead of a closed mid level low over the Red River
Valley. The GOES-16 clean IR loop showed a divergence signature
across MS/AL, though tops have been slowly warming over the past
couple of hours. The convection lies within an axis of 1000-1500
J/KG of MLCAPE, while the precipitable water axis lies to the west
of the best instability.

Hourly rainfall rates have dropped a bit across MS during the past
hour or so, though the KDGX radar still shows hourly rates between
1.50/2.00 inches over Leak County MS. Though the convective line
is moving east, convective elements are still moving northeast
along it (with the 850-300 mb mean wind). This should allow hourly
rainfall rates to remain close to 1.50 inches as the storms cross
northeast MS into northern AL. These rates are similar to those
shown by the most recent HRRR runs.

As the mid level circulation moves east, the propagation vectors
become more westerly, and this should allow the convection to
become even more linear, especially across southern AL into GA.
When that occurs, the threat of flash flooding is expected to
diminish. Based on high resolution simulated reflectivity, this is
expected to occurs before 14/07z over central and southern AL.

Moderate to heavy rainfall follows in the wake of the deeper
convection, away from the best instability closer to the Gulf of
Mexico. The additional rainfall could result in runoff issues
further north into portions of TN.

Hayes


ATTN...WFO...BMX...HUN...JAN...MEG...OHX...

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

LAT...LON   35008662 34108639 33368660 32788716 32178891
            32578934 33258920 34328853 35008771