Mesoscale Precipitation Discussion 0809
NWS Weather Prediction Center College Park MD
1157 PM EDT Sat Sep 08 2018

Areas affected...Ext Northwest NC...Southwest VA...Southeast WV...

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

Valid 090400Z - 090730Z

SUMMARY...Increasing convection with some potential training
through complex terrain may pose isolated flash flooding concerns.

DISCUSSION...While main mid-level height falls approach from the
west amplifying warm sector across the Cumberland Plateau and up
the western flanks of the Appalachians...the cold front in the
Mid-Atlantic continues to lead to some cold air damming along the
front range.  As such the frontal boundary is bulged through the
VA/N NC mountains favorably for strong upslope/sfc moisture
convergence.  With Tds in the upper 60s and some spot low 70s,
there remains ample moisture for efficient rainfall, especially
given 15kts of 850mb flow over the cold sector in SW VA further
enhancing low level forcing.  Mean cloud bearing flow is a bit off
angle from the frontal zone but back toward the apex of the cold
front in far NW NC...cells have a better probability for
training/repeat tracks as the lift NNE.  As such 1.5-2.5" totals
are possible, which is in the vicinity of eclipsing the lower 1 or
3 hr FFG values in the area.

While dynamic forcing/upper level ascent will be stronger further
north, there is a bit less moisture/moisture flux to aid cells
across SW WV.  Even lower FFG (less than 1.2"/1hr) further north
in WV, also suggests the scattered 1-1.5" totals here may also
exceed FFG for possible flash flooding in the next few hours. 

Slow eastward propagation vectors and slow advancement of warm air
sector should shift focus of convection further east into higher
FFG toward 07z, reducing the overall potential after that time. 

Gallina

ATTN...WFO...LWX...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...

LAT...LON   38687996 38407922 38067895 37497926 36967987
            36148094 36228155 37068139 38158108 38548056