MESOSCALE PRECIPITATION DISCUSSION 0730
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 PM EDT SAT OCT 08 2016
 
AREAS AFFECTED...NORTHEASTERN SC...CENTRAL AND EASTERN
NC...SOUTHEASTERN VA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 081849Z - 090100Z
 
SUMMARY...HURRICANE MATTHEW IS EXPECTED TO PRODUCE AN ADDITIONAL
3-8 INCHES OF RAINFALL...WITH LOCALLY HIGHER AMOUNTS...THROUGH 9
PM 

DISCUSSION...AT 18Z...NHC PLACED THE CENTER OF HURRICANE MATTHEW
NEAR MYRTLE BEACH, SC, AND MOVING NORTHEASTWARD. ADDITIONALLY, A
QUASI-STATIONARY COASTAL FRONT WAS ANALYZED JUST INLAND FROM THE
COAST OF THE CAROLINAS. INFRARED SATELLITE IMAGERY SHOW THAT CLOUD
TOPS AROUND THE CENTER OF MATTHEW HAVE WARMED OVER THE PAST
SEVERAL HOURS. AS CONVECTION AT THE CORE OF MATTHEW LOSES
INTENSITY, THE MAIN FOCUS FOR HEAVY RAINFALL HAS SHIFTED INLAND,
NORTH AND WEST OF THE FRONT. WIDESPREAD RAINFALL RATES AROUND 1
IN/HR ARE OCCURRING PER LATEST MRMS DATA. IN A COUPLE HEAVIER
BANDS, RAINFALL RATES AS HIGH AS 2-3 IN/HR ARE BEING OBSERVED.
NUMEROUS REPORTS OF SIGNIFICANT FLASH FLOODING HAVE BEEN RECEIVED
SO FAR THIS AFTERNOON ACROSS THE CAROLINAS.

INSTABILITY REMAINS MARGINAL PER LATEST SPC MESOANALYSIS, WITH
MOST UNSTABLE CAPES IN THE 500-1000 J/KG RANGE SOUTH/EAST OF THE
STATIONARY FRONT AND IN THE 100-500 J/KG RANGE JUST NORTH/WEST OF
THE FRONT. GIVEN THE STRONG AND BROAD 50-65 KT LOW-LEVEL
CROSS-FRONTAL FLOW, THIS INSTABILITY IS SUFFICIENT TO SUPPORT
THESE VERY HEAVY RAINFALL RATES.

PER THE LATEST RAP RUN, A BAND OF STRONG FRONTOGENETIC FORCING
NORTH/WEST OF THE FRONT IS FORECAST TO PERSIST OR EVEN STRENGTHEN
AS LOW-LEVEL WINDS ON THE COLD SIDE OF THE FRONT BACK IN RESPONSE
TO THE CENTER OF MATTHEW MOVING NORTHEASTWARD. AS A RESULT, WOULD
EXPECT THE POTENTIAL FOR INCREASING COVERAGE OF 2 IN/HR RAINFALL
RATES. THE LATEST HRRR TIME-LAGGED ENSEMBLE DOES INDEED SHOW THE
PROBABILITIES FOR 2+ IN/HR RAIN RATES INCREASING THROUGH THE
REMAINDER OF THE AFTERNOON ALONG AND JUST ON THE COOL SIDE OF THE
FRONT. 

NUMEROUS HI-RES MODELS INCLUDING THE HRRR/HRRR-EXPERIMENTAL,
WRF-ARW/NMM, AND NSSL-WRF INDICATE THE POTENTIAL FOR 3-8 INCH
ADDITIONAL RAINFALL AMOUNTS INLAND FROM THE FRONT OVER THE NEXT
SEVERAL HOURS, WITH LOCALIZED AMOUNTS EXCEEDING 9 INCHES NOT OUT
OF THE QUESTION. GIVEN THE ONGOING WIDESPREAD FLASH FLOODING, AND
THE POTENTIAL FOR THESE ADDITIONAL EXCESSIVE RAINFALL AMOUNTS,
POTENTIALLY LIFE-THREATENING FLASH FLOODING IS LIKELY.

RYAN

ATTN...WFO...AKQ...CAE...ILM...MHX...RAH...RNK...

ATTN...RFC...MARFC...SERFC...

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            35137548 34717624 34307717 33917775 33787842 
            33787894 33937944 34257979 34637986 35557982 
            36407921 36757871 37127796