Graphic for MPD #0216

MESOSCALE PRECIPITATION DISCUSSION 0216
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
558 PM EDT FRI MAY 12 2017

AREAS AFFECTED...NORTHEAST TN...SOUTHWEST VA...FAR NORTHWEST NC

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 122157Z - 130300Z

SUMMARY...SOME ADDITIONAL ROUNDS OF SHOWERS AND THUNDERSTORMS
THROUGH THE EVENING WILL MAINTAIN THE THREAT FOR RUNOFF PROBLEMS
AND PERHAPS SOME FLASH FLOODING.

DISCUSSION...AN AXIS OF WEAK WARM SECTOR INSTABILITY CONTINUES TO
NOSE UP ACROSS FAR EASTERN TN LATE THIS AFTERNOON JUST AHEAD OF A
COLD FRONT AND WITH SUPPORT FROM AN AREA OF LOW PRESSURE NEAR THE
VA/TN BORDER. SUFFICIENT BOUNDARY LAYER DESTABILIZATION COUPLED
WITH SURFACE CONVERGENCE AND LOCALIZED OROGRAPHIC ASCENT HAS
ALLOWED MULTIPLE BANDS OF HEAVY SHOWERS AND THUNDERSTORMS TO
IMPACT THE WEST-FACING SLOPES OF THE SMOKY MOUNTAIN CREST ALONG
WITH ADJACENT AREAS OF NORTHEAST TN AND SOUTHWEST VA. THE
EXPERIMENTAL GOES-16 IR SATELLITE IMAGERY HAS SHOWN SOME RATHER
IMPRESSIVELY COLD CONVECTIVE TOPS OVER NORTHEAST TN OVER THE LAST
30 MINUTES WHICH IS SUGGESTIVE OF INTENSE RAINFALL RATES WITH THE
ONGOING THUNDERSTORM ACTIVITY. IN FACT...DUAL-POL RADAR ESTIMATES
HAVE BEEN UPWARDS OF 1.25 TO 1.5 INCHES/HR LOCALLY.

ADDITIONAL SHOWER AND THUNDERSTORM ACTIVITY IS EXPECTED THROUGH
THE EVENING ACROSS NORTHEAST TN AND INTO SOUTHWEST VA AS A
SHORTWAVE TROUGH CROSSES THE TN VALLEY. THE LATEST HRRR GUIDANCE
SUPPORTS AN ADDITIONAL 1.5 TO 2 INCHES OF OROGRAPHICALLY ENHANCED
RAIN NEAR THE VA/TN BORDER AND ALSO OVER THE SMOKY MOUNTAINS ALONG
AND ADJACENT THE NC/TN BORDER THROUGH 03Z. GIVEN SOME OF THE
EARLIER HEAVY RAINFALL...THESE ADDITIONAL RAINS MAY ENHANCE THE
THREAT OF RUNOFF PROBLEMS THROUGH THE EVENING WITH SOME FLASH
FLOODING ALSO POSSIBLE.

ORRISON

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

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

LAT...LON   37308109 37098061 36828082 36328140 35908238
            35638317 35518397 35778408 36348344 36798283
            37158211


Last Updated: 558 PM EDT FRI MAY 12 2017