Mesoscale Precipitation Discussion 0536
NWS Weather Prediction Center College Park MD
1057 PM EDT Tue Jul 24 2018

Areas affected...Southwest VA & Western NC

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

Valid 250256Z - 250556Z

Summary...Thunderstorms are increasing in coverage across western
NC and southwest VA.  Hourly rain totals to 2" with local amounts
to 4" are possible.

Discussion...A pre-frontal trough is acting as a focus for loosely
organized convection across the area.  Inflow at 850 hPa is
convergent out of the south to southwest at 15-20 kts, importing
ML CAPE values of 500-1500 J/kg into the area.  The main upper low
across far southwest VA and a companion circulation to its east
are acting to enhance upper level outflow.  Precipitable water
values of 1.6-1.8" lie across the region per 00z soundings.

While convection is mostly pulse, cell collisions and very short
bouts of training appear to be the main heavy rain threat.  An
additional outflow boundary moving into the region from earlier
convection in western NC will likely aid cell coverage in short
order.  Soils in the area are partially saturated from recent
rains, adding to the risk.  The mesoscale guidance advertises
local amounts in the 3-4" range over the next several hours. 
Radar estimates have peaked in the 1.5-2" an hour range, so this
seems achievable wherever storms can persist for a couple hours.

Roth

ATTN...WFO...GSP...RAH...RNK...

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

LAT...LON   37147868 35897960 35488095 35498163 36658012