Mesoscale Precipitation Discussion 1015
NWS Weather Prediction Center College Park MD
739 AM EST Mon Nov 12 2018

Areas affected...Near the AL/FL panhandle border

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

Valid 121238Z - 121808Z

Summary...Thunderstorms with heavy rain are lifting slowly into
the region near and north of a warm front.  Hourly rain totals to
2.5" and local amounts of 4-7" are possible over the next several
hours.

Discussion...Surface observations indicate that a synoptic scale
warm front is lifting slowly northeast into sections of the
central and eastern Gulf coast to the east of a weak wave of low
pressure in southeast LA.  Precipitable water values are 1.7-1.9"
per GPS data, with values of 2"+ expected to move into the area
this morning per RAP forecast fields.  ML CAPE values of 500-1500
J/kg lie just offshore, with trends indicating some movement
ashore in the near future.  Aloft, the area is in a divergent area
near a segment of the subtropical jet stream, with indications of
a shortwave moving across southeast LA in recent GOES-16 water
vapor imagery.  Radar imagery shows a couple weak convective
vorticity maxima moving across the Chandeleur Islands/Shoals
towards Dauphin Island at the present time, with another possible
weak vorticity maximum lifting into south-central AL.  Inflow at
850 hPa is convergent at 30-40 kts per VAD wind profiles. 
Effective bulk shear of 30-50 kts (per SPC mesoanalyses) appears
to be leading to convective organization, with some apparent
mesocyclones offshore per recent radar imagery.

A combination of backbuilding, training, and mesocyclones moving
into the area are expected to lead to hourly rain totals to 2.5"
as instability is forecast to continue to surge ashore.  An
eastward adjusted 06z NAM CONEST (4 km NAM) and 00z WRF NSSL
appear to have the best grasp of this activity.  They indicate
local amounts in the 4-7" range, which is possible should the
storms move/stay ashore for 2-3 hours.

Roth

ATTN...WFO...LIX...MOB...TAE...

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

LAT...LON   31178687 30918635 30398634 30228745 30208862
            30768798 31088736