WPC Met Watch |
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Mesoscale Precipitation Discussion: #0228 (2018) |
(Issued at 820 PM EDT TUE MAY 29 2018
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MPD Selection |
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MESOSCALE PRECIPITATION DISCUSSION 0228
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
820 PM EDT TUE MAY 29 2018
AREAS AFFECTED...UPSTATE SC...WESTERN NC...EXT SW VA...
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 300018Z - 300618Z
SUMMARY...STRONG OROGRAPHIC ASCENT OVER SATURATED GROUNDS
COMPOUNDED BY A N-S CONVERGENCE BAND WITH TRAINING ELEMENTS
LIFTING NORTH INTO THE TERRAIN PRESENT HIGH LIKELIHOOD FOR
CONTINUED FLASH FLOODING
DISCUSSION...STRONG WARM CONVEYOR BELT CONTINUES TO PUMP VERY DEEP
MOIST TROPICAL AIR NORTH AND NORTHWESTWARD ACROSS THE CAROLINAS
DIRECTLY INTO THE SOUTHERN APPALACHIANS FROM EXT N GA TO SW VA.
RADAR MOSAIC ALSO DEPICTS A N-S SOUTH LINE OF DEEPER CONVECTION
FROM N AIKEN COUNTY, SC TOWARD HENDERSON COUNTY, NC AT THE WESTERN
EDGE OF THE WARM CONVEYOR BELT WHERE MAXIMIZED LOW LEVEL
CONVERGENCE/FLUX SUPPORT TROPICAL UPDRAFTS CAPABLE OF 2"/HR RATES.
GREATEST DENSITY OF SHALLOW CONVECTION IS ALONG AND NORTHEAST OF
THIS CONVERGENCE LINE RECEIVING SUFFICIENT OROGRAPHIC ASCENT
ACROSS THE FOOTHILLS OF NC AND STARTING TO LEAK INTO SW VA. RAP
ANALYSIS AND SATELLITE DERIVED AMV SUGGEST GREATEST UPPER LEVEL
DIVERGENCE OVER W NC AS THE WARM CONVEYOR SPLITS TOWARD ALBERTO AS
WELL AS NE AROUND BERMUDA RIDGE. WITH HIGH RATES, TRAINING AND
OROGRAPHIC ENHANCEMENT ADDITIONAL 2-4" TOTALS ARE EXPECTED FROM
HENDERSON TO CALDWELL COUNTIES WHERE FFG VALUES ARE ALREADY BELOW
1" EVEN IN 3HRS. MAKING FLASH FLOODING HIGHLY LIKELY WITH
NEIGHBORHOOD PROBABILITIES EXCEEDING FFG VALUES (WHICH WERE
CALCULATED HIGHER FROM 12Z FFG VALUES) WAS ALREADY NEAR 90%.
THE NORTHWARD SHIFT OF BEST DIFFLUENCE WITH A STRENGTHENING UL JET
(TO 50KTS) WILL MAINTAIN SHOWERS/THUNDERSTORMS EVEN WITH THE SLOW
AND EVENTUAL LOSS OF BEST INSTABILITY (BELOW 500 J/KG MUCAPES
TOWARD 07Z) WILL CONTINUE TO TRACK NORTH. SLOW EASTWARD MARCHING
OF THE CONVERGENCE BAND WILL ALLOW FOR A LONGER DURATION OF HEAVY
RAIN AXIS INTO THE LOWEST FFG VALUES WITH THE TAIL END OF THE BEST
FORCING TO SUBSIDE TOWARD 07Z...THOUGH SCATTERED LIGHT TO MODERATE
LINGERING SHOWERS MAY REMAIN.
GALLINA
ATTN...WFO...CAE...GSP...MRX...RAH...RNK...
ATTN...RFC...LMRFC...OHRFC...SERFC...
LAT...LON 36928046 36627989 36008009 35618014 35218035
34238106 34088141 33898192 33978203 34518233
34948273 35288325 35618335 35788322 36118260
36548177
Last Updated: 820 PM EDT TUE MAY 29 2018
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