643  
AWUS01 KWNH 152133  
FFGMPD  
PAZ000-WVZ000-OHZ000-160330-  
 
MESOSCALE PRECIPITATION DISCUSSION 0017  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
432 PM EST THU FEB 15 2018  
 
AREAS AFFECTED...CTRL/ERN OH...PANHANDLE OF WV...SWRN/SCTRL PA  
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE  
 
VALID 152130Z - 160330Z  
 
SUMMARY...HEAVY RAIN BANDS APPEAR LIKELY TO DEVELOP BY 6 PM EST  
AND THEN TRAIN IN A WEST-TO-EAST FASHION ALONG THE I-70 CORRIDOR  
THIS EVENING. HOURLY RAIN RATES APPROACHING 1 IN/HR EMBEDDED  
WITHIN STEADY RAIN THROUGH THE EVENING MAY PRODUCE AREAS OF  
LOCALIZED FLASH FLOODING.  
 
DISCUSSION...THE LATEST SURFACE OBSERVATIONS AND RAP OBJECTIVE  
ANALYSIS DEPICTED BROAD...MOIST...SOUTHWESTERLY LOW-LEVEL INFLOW  
ACROSS THE OHIO VALLEY REGION. THE CINCINNATI (KCVG) ASOS RECORDED  
A DEWPOINT OF 64 DEGREES AT 20Z...WHICH HAS NOT BEEN PREVIOUSLY  
REPORTED ON AN HOURLY OBSERVATION IN FEBRUARY (PERIOD OF RECORD  
1947-PRESENT). THIS IS AN ISOLATED EXAMPLE...BUT IS INDICATIVE OF  
ANOMALOUSLY HIGH LOW-LEVEL MOISTURE VALUES FOR FEBRUARY ACROSS THE  
REGION. AS THE BOUNDARY LAYER FLOW REACHES THE SURFACE WARM  
FRONT...IT WAS BECOMING INCREASINGLY VEERED TO A WESTERLY  
DIRECTION. AND THROUGH THE DEPTH OF THE TROPOSPHERE...STREAMLINES  
WERE GENERALLY CONVERGING INTO DEEP WESTERLY FLOW. THIS WOULD  
FAVOR TRAINING RAIN BANDS...AS WOULD THE ORIENTATION OF THE  
LOW-LEVEL INFLOW (FROM THE WSW FAVORING BACKBUILDING).  
 
REGIONAL RADARS WERE SHOWING AN INCREASE IN REFLECTIVITY BETWEEN  
20Z AND 2130Z JUST NORTH OF THE I-70 CORRIDOR...AND SEVERAL  
LIGHTNING STRIKES HAD ALSO BEEN RECENTLY OBSERVED TO THE NORTHEAST  
OF DAYTON OH. HI-RES MODELS ARE IN GOOD AGREEMENT THAT THIS  
WEST-TO-EAST ORIENTED BAND OF HEAVIER RAIN WITH EMBEDDED  
THUNDERSTORMS SHOULD CONTINUE TO ORGANIZE OVER THE NEXT COUPLE  
HOURS AND TRAIN NEAR I-70 INTO THE EVENING HOURS. RECENT RUNS OF  
THE HRRR AND NAM NEST BOTH SHOW THE POTENTIAL FOR HOURLY RAIN  
RATES TO APPROACH OR EVEN EXCEED 1 IN/HR IN NARROW AND LOCALIZED  
SWATHS DURING THE EVENING HOURS. NEARLY ALL HI-RES MODELS SHOW  
LOCALIZED 6-HOUR RAINFALL MAXIMA ON THE ORDER OF 2-3 INCHES BY  
03Z. THESE AMOUNTS MAY BE SUFFICIENT TO PRODUCE FLASH  
FLOODING...PARTICULARLY IN URBANIZED AREAS OR SMALLER BASINS  
EMBEDDED WITHIN SHARPER TERRAIN GRADIENTS.  
 
THE AREA AROUND PITTSBURGH IN SOUTHWEST PENNSYLVANIA AND THE WEST  
VIRGINIA PANHANDLE HAS SOME OF THE LOWEST FFG IN THE OUTLINED  
AREA...AND THE 60-DAY PRECIPITATION ANOMALIES ARE HIGHEST IN THE  
SAME AREA (NEAR OR IN EXCESS OF 150 PERCENT OF NORMAL). HI-RES  
MODELS SHOW A CONSIDERABLE OVERLAP OF THE HEAVIER RAINFALL OVER  
THE NEXT SIX HOURS...AND THEREFORE THIS IS A REGION THAT MAY BE  
MORE HYDROLOGICALLY FAVORED FOR FLASH FLOODING.  
 
LAMERS  
   
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
 
 
ATTN...WFO...CLE...CTP...ILN...PBZ...RLX...  
 
ATTN...RFC...MARFC...OHRFC...  
 
LAT...LON 41068009 40927835 40527752 40097767 39817856  
39808008 39798283 40078373 40738329 41028172  
 
 
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