Graphic for MPD #0691

Mesoscale Precipitation Discussion 0691
NWS Weather Prediction Center College Park MD
1103 PM EDT Sat Aug 18 2018

Areas affected...Central and Eastern North Carolina

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

Valid 190302Z - 190700Z

Summary...Showers and thunderstorms will continue to coalesce into
clusters and lines and move repeatedly over the same locations in
central and eastern North Carolina. This situation favors locally
heavy rainfall and the possibility of flash flooding. Rain rates
may peak around 2-3 in/hr where strong storms can be sustained.

Discussion...Regional radars showed numerous convective clusters
or small convective lines oriented roughly parallel to the deep
layer mean wind over central and eastern North Carolina, along a
line from VUJ-JNX and RWI-ECG. Additional low-topped convection,
in the form of rain showers, was developing along I-95 closer to
FAY, and may begin to merge with the more organized convective
lines to the north in the next couple hours based on current radar
trends. This convection was developing in a broad area of
confluent low-level flow and an enhancement in the 925-850mb
moisture transport. This low-level flow pattern should favor new
convection becoming channeled into existing bands of heavy rain
and maintaining the training pattern over the next few hours.
Therefore, flash flooding appears possible over central and
eastern North Carolina.

The environment also favors continuation of ongoing convection,
with moderate instability (MLCAPE 1000-1500 j/kg, weak CINH) and
deep moisture (GPS-PW obs over 2 inches). CIRA layer PW above
700mb shows a notable enhancement over the eastern half of North
Carolina, and the nearly saturated profile through much of the
depth of the troposphere should favor efficient rainfall
production. MRMS and KRAX dual pol estimates have already shown
rain rates approaching 3 in/hr, and in an environment with deep
moisture and PWs approaching 2.2-2.3 inches in some pockets, this
does not seem unreasonable. KRAX shows KDP values around 2 deg/km
in most of the stronger convection, with ZDR around 1 dB,
indicative of fairly high concentrations of small water droplets
(and warm rain processes being more dominant). Given the potential
for 2-3 in/hr rain rates, flash flooding will be possible across
the region until the convection begins to exit the area in several
hours.

Lamers

ATTN...WFO...AKQ...MHX...RAH...

ATTN...RFC...MARFC...SERFC...

LAT...LON   36857605 36227540 35607546 35157732 35017880
            35298000 35747987 36367822


Last Updated: 1103 PM EDT Sat Aug 18 2018