Mesoscale Precipitation Discussion 0850
NWS Weather Prediction Center College Park MD
1116 AM EDT Sun Sep 16 2018

Areas affected...Eastern TN...Western NC...Southwestern VA...

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

Valid 161515Z - 162115Z

SUMMARY...Strengthening orographic ascent will increase rainfall
rates and lead to likely flash flooding.  Sufficient mid-level
moisture may bleed over the western flanks posing some possible
flash flooding threat there too.

DISCUSSION...VWP network from KFCX and TCLT and RAP analysis
denote slight backing of the 925-850mb winds to nearly easterly
and even KMRX is showing signs of backing at 850mb after some
down-sloping.  Winds are also enhanced from 50-55kts and starting
to impinge nearing orthogonality (or forecast best intersection at
80 to 90 degrees).  This low level jet streak is accompanied by
enhanced moisture flux with total PWATs in excess of 2" with CIRA
LPW SFC-850 values at an incredible 1.25" which suggests
orographic enhancement with .75-1"/hr possible over the next few
hours.  Totals of 3-4" are well within the realm of possibility
with some totals at higher peaks potentially higher, especially at
the nose of this jet from windward facing topography from the
NC/VA border to the NC/SC border  This should lead to rapid
response of streams and pose likely flash flooding in the next few
hours as denoted by the CANE river rising 7ft in less than 3hrs
per LSR from NWSFO GSP.

Given the moisture flux above 850mb, LPWs in the 850-7H range
still at .6-.75" and generally convergence due to the backing of
the winds, moderate rain showers along the western flanks of the
terrain into the Cumberland Plateau could reach 6-hour totals of
1-1.5" and potential runoff issues.

Gallina

ATTN...WFO...GSP...JKL...MRX...RLX...RNK...

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

LAT...LON   37078170 37078084 36778030 36468036 36058069
            35968087 35868122 35398187 35098324 35108421
            35778441 36288459 36518443 36558378 36678336
            37008259