Mesoscale Precipitation Discussion 0797
NWS Weather Prediction Center College Park MD
909 PM EDT Fri Sep 07 2018

Areas affected...Central Ohio Valley through Central Mid-Atlantic

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

Valid 080110Z - 080530Z

SUMMARY...Continued flash flooding threat for remaining deep
convection though overall trend/coverage reducing with time.

DISCUSSION...Regional RADAR mosaic and GOES-16 10.3um channel
continue to show scattered convective cells along the stationary
boundary from the central Ohio Valley to the Mid-Atlantic. 
General cloud tops and Reflectivity denote overall
warming/downward trends though isolated pockets of cells currently
over S central OH into W WV and near the DC and Wilmington,DE and
southern NJ have some cooling cells with increased lightning. 
Many of these cells are propagating on older outflow and seeking
remaining pockets of instability.  As such a few more hours remain
for these cells to survive. 

The environment for the remaining cells remains very rich/deep in
moisture and given mean mid-level flow is weak between exiting jet
streak/trof off the Northeast and the amplification of the
approaching trof in the MO River Valley; cell motions are very
slow allowing for heavy rainfall.  Blended TPW and RAP analysis
denote values over 2" in the Mid-Atlantic and 1.75-2" across the
Ohio Valley.  As such 1-2 hour duration with slow cells and rates
of 2"/hr support totals in the 2-4" range likely.

The greatest threat for prolonged convective development is across
the Mid-Atlantic over N VA/S Central MD and the Southern Delmarva,
where the atmosphere has remained untapped and instability values
remain above 2000 J/kg.  If current cells can support enough
outflow for convergence...there is some threat across this region
a bit longer in time...though there is much higher uncertainty
given the current setup/convection.

Gallina

ATTN...WFO...AKQ...ILN...LWX...PBZ...PHI...RLX...

ATTN...RFC...MARFC...OHRFC...

LAT...LON   39737515 39037554 38017595 38417835 38408014
            38208252 38598355 38918447 39468467 39728440
            39548350 39288181 39218046 39117929 39277827
            39567729 39647652