MESOSCALE PRECIPITATION DISCUSSION 0727
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1145 PM EDT FRI OCT 07 2016
 
AREAS AFFECTED...WEST VIRGINIA...SOUTHWEST PENNSYLVANIA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 080345Z - 080945Z
 
SUMMARY...DEEP SATURATED PROFILE TO REMAIN FAIRLY
STEADY/STATIONARY OVER THE MORNING HOURS INCREASING THE THREAT FOR
FLOODING CONDITIONS.

DISCUSSION...SYNOPTIC SETUP IDEAL FOR CONFLUENT MOISTURE STREAM
FOR PERSISTENT MODERATE RAINFALL.  THOUGH MAIN SHORTWAVE HAS
LIFTED WELL NORTH INTO CANADA...A LINGERING TROF EXISTS ACROSS THE
GREAT LAKES...WITH EXPANDING ANTICYCLONIC OUTFLOW FROM TROPICAL
CYCLONE MATTHEW PROVIDING GOOD UPPER LEVEL EVACUATION AND BROAD
SCALE ASCENT IN THE DIFFLUENT REGION ACROSS THE CENTRAL
APPALACHIANS.   IN THE LOWER LEVELS...RETURN FLOW ACROSS N NC/S VA
INTO THE SOUTHERN BLUE RIDGE TURNS NORTHWEST AND NORTHWARD
PROVIDING A FOCUSING CONFLUENT CHANNEL ACROSS THE SAME AREA. 
GIVEN PROXIMITY TO TROPICAL MOISTURE AND CONFLUENT MST
FLOWS...TPWS HAVE INCREASED TO 1.75" WITH NEARLY SATURATED
PROFILES THROUGH A VERY DEEP LAYER PER NEARBY 00Z RAOBS
(PIT/RNK/GSO) AND RAP FCST SOUNDINGS.  SOME SHALLOW INSTABILITY
DOES RESIDE WITHIN THESE PROFILES IN THE 100-250 J/KG RANGE TO
HELP SUPPORT SOME ADDITION SHALLOW UPDRAFTS/ASCENT AND MAY LEAD TO
SOME HIGHLY LOCALIZED RATES UP TO .75"/HR.  

CURRENT WV/RADAR MOSAIC ALSO INDICATES A WEAK WAVE LIFTING OUT OF
SW VA INTO S WV ATTM...SLOW PROGRESSION OF THE TROF FROM THE WEST
WILL CONTINUE TO TIGHTEN THE GRADIENT AND POTENTIALLY ENHANCE
SHOWERS EVEN FURTHER.   STILL OBS 1 HOUR RATES ABOUT .5"/HR ARE
MARGINAL FOR SHORT TERM FLASH FLOOD CONCERNS HOWEVER... 6HR TOTALS
ARE ALREADY REACHING 1.25-1.5" ACROSS CENTRAL WV WHICH IS VERY
NEAR 6HR FF GUIDANCE VALUES.  HI-RES CAMS AND GLOBAL MODELS SHOW
STRONG AGREEMENT FOR THIS PERSISTENT CHANNEL ACROSS CENTRAL WV/W
PA WITH RATES OF .25-.5"/HR FOR ADDITIONAL 6HR TOTALS IN THE 1-3"
RANGE INCREASING STREAM FLOWS.  GIVEN GFS/HRRR SEEM TO BE HANDLING
THE SITUATION WELL...NATIONAL WATER MODEL STREAM FLOWS TO MUCH
ABOVE NORMAL ARE OCCURRING BY 09Z IN THE AREA OF CONCERN.        

GALLINA

ATTN...WFO...CTP...PBZ...RLX...RNK...

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

LAT...LON   40957885 40457877 39517936 38807978 37718037 
            37468068 37358123 37788157 39048125 40028029 
            40607972