WPC Met Watch |
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Mesoscale Precipitation Discussion: #0853 (2018) |
(Issued at 1130 PM EDT Sun Sep 16 2018
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MPD Selection |
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Mesoscale Precipitation Discussion 0853
NWS Weather Prediction Center College Park MD
1130 PM EDT Sun Sep 16 2018
Areas affected...western NC/VA into southeastern WV
Concerning...Heavy rainfall...Flash flooding likely
Valid 170328Z - 170915Z
Summary...A high threat for flash flooding will continue from the
Piedmont into the Appalachians of NC, SC and WV. 2-4 inches
between 03-09Z can be expected with rain rates between 0.5 and 1.5
in/hr.
Discussion...Regional radar imagery across the central
Appalachians into the Piedmont showed widespread light to moderate
stratiform rain with embedded heavier elements. Observed rainfall
rates and peak dual-pol estimates (KFCX, KRAX) have generally
ranged between 0.5 and 1.5 in/hr over the past couple of hours.
00Z soundings from RNK and GSO showed instability was weak at less
than 500 J/kg with precipitable water values ranging between 1.8
and 2.3 inches. VAD wind data and RAP analyses showed
east-southeasterly 850 mb flow of 40-50 kt, stretching from
central NC into western VA and the KY/WV border. Instability
appeared to be the greatest limiting factor for higher rates but
nonetheless, 3-6+ inches of rain have already fallen across large
sections of the area through the day on Sunday.
Surface and 00Z upper air data showed that Tropical Depression
Florence's low level center and mid-level center are becoming more
displaced from one another. VAD wind data showed the 850 mb low
from Florence was located over the southern TN/NC border at 03Z,
with a RAP forecast track toward the north-northwest through 09Z.
This track will allow 850 mb winds to veer toward a more southerly
direction across western NC/VA through 09Z allowing stronger
moisture flux to move north toward the central VA/WV border. There
is no significant change in MUCAPE forecast through the morning
for these areas, so continued 0.5-1.5 in/hr rain rates should be
expected at times within elements of training heavy rain cores. An
additional 2-4 inches of rain is expected (locally higher) through
09Z which given the sensitive terrain and wet antecedent
conditions, makes flash flooding likely.
Otto
ATTN...WFO...GSP...LWX...MRX...RAH...RLX...RNK...
ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...
LAT...LON 38477981 38047908 37187890 36357896 35987935
35887984 36108040 36078089 35748155 35668203
35758226 35918233 36188208 36428175 36658159
37188161 37678127 38078070 38348020
Last Updated: 1130 PM EDT Sun Sep 16 2018
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