Flash Flood Guidance
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000
AWUS01 KWNH 271802
FFGMPD
VAZ000-WVZ000-OHZ000-KYZ000-272300-

MESOSCALE PRECIPITATION DISCUSSION 0575
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
201 PM EDT THU JUL 27 2017

AREAS AFFECTED...SOUTEHERN WV...EASTERN KY...EXT SOUTHERN
OH...SOUTHWEST VA

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

VALID 271800Z - 272300Z

SUMMARY...FEW ROUNDS OF HEAVY RAIN POSE FLASH FLOODING THREAT
THROUGH EVENING ACROSS FOOTHILLS AND CENTRAL APPALACHIANS.

DISCUSSION...EXP. GOES-16 CONUS IMAGERY SUITE DEPICTS A SMALL
SHORTWAVE AT THE FAR EASTERN EXTENSION OF WARM CONVEYOR BELT WHERE
LOW LEVEL FLOW EVEN HAS FLATTENED TO DUE WESTERLY SUPPORTING A
STRONG LINE OF CONVECTION CROSSING THE CENTRAL APPALACHIANS.  THIS
LOW LEVEL WESTERLY FLOW PROVIDES STRONG MST TRANSPORT INTO THE
REAR OF THE CONVECTIVE LINE ALLOWING FOR SOLID CONVERGENCE ATTM.

AREA OF CONCERN IS ALSO AT THE EASTERN PERIPHERY OF FAVORABLE
UPPER LEVEL DIFFLUENCE FROM WNW 3H JET AND MODEST INSTABILITY AND
TPWS UP TO 2.0" THERE HAS BEEN INCREASING EFFICIENCY TO CELLS ON
THE LINE.  RAIN RATES ARE ON AVERAGE 2.0"/HR THOUGH FORWARD
PROGRESS OF THE LINE HAS BEEN LIMITING TOTALS BASED ON OBSERVATION
NETWORK TO AT MOST 1.8"/HR AND 2.07" TOTAL AT KERMIT IFLOWS GAUGE
WITH NUMEROUS OTHER SITES IN THE 1.5" RANGE.  THIS IS JUST AT THE
CUSP OF LOCAL FFG VALUES AND IS NOT LIKELY TO EXCEED AS THE LINE
ROLLS INTO SW VA IN THE NEXT FEW HOURS.  HOWEVER...THIS IS ONLY
PRIMING THE AREA FOR POTENTIAL FLASH FLOODING WITH THE NEXT BOUT.

WEAK DPVA ALONG SE FLANK OF MID-LEVEL SHORTWAVE SEEN IN WV/VISIBLE
IMAGERY OVER N CENTRAL OHIO AND STRONG UPPER LEVEL FLOW AND
ACCOMPANYING DIFFLUENCE ALLOW FOR A FAVORABLE REGION FOR UPSTREAM
DEVELOPMENT OVER S OH/E KY OVER THE NEXT FEW HOURS.  FILTERED
SOLAR INSOLATION HAS ALLOWED SURFACE TEMPS TO REBOUND TO THE
MID-UPPER 80S ACROSS CENTRAL KY WITH TDS IN THE LOW TO MID 70S
SUPPORTING SBCAPES TO 2500 J/KG. WHILE MST FLUX IS A BIT LESSENED
THAN FURTHER EAST THERE IS SUFFICIENT MOISTURE TO SUPPORT ANOTHER
CONVECTIVE LINE CAPABLE OF 1.5-2"/HR RATES.

RAPID REFRESH HI-RES CAMS SUCH AS THE HRRR AND ESRL HRRRV3 SUGGEST
THE LINE TO DEVELOP IN THE NEXT 1-2 HOURS THOUGH RECENT IR/VIS
TRENDS INDICATE CONVECTIVE INITIATION HAS TAKEN PLACE ACROSS LEWIS
COUNTY KY WITH OTHER TOWERS FURTHER SW IN THE INSTABILITY AXIS.
EXPECT HRRR/HRRRX SOLUTIONS TO LAG IN TIME BUT EVOLVE PROPERLY
WITH AN ADDITIONAL 2-3" TOTALS EXPECTED. THIS SHORTENS THE TIME
FROM THE FIRST BOUT...SUGGESTING FLASH FLOODING MAY BE POSSIBLE
GIVEN WATER IN THE SYSTEM.

GALLINA

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...ILN...JKL...MRX...RLX...RNK...

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

LAT...LON   39188271 38998169 38297992 37597900 36697934
            36678185 36728389 37738375 38428369



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