Weather Prediction Center issues Mesoscale Precipitation Discussion #708 concerning HEAVY RAINFALL...FLASH FLOODING LIKELY032
AWUS01 KWNH 231802
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MDZ000-VAZ000-NCZ000-WVZ000-SCZ000-TNZ000-KYZ000-240000-
Mesoscale Precipitation Discussion 0708
NWS Weather Prediction Center College Park MD
201 PM EDT Tue Jul 23 2024
Areas affected...Southern Mid-Atlantic into portions of the
Appalachians
Concerning...Heavy rainfall...Flash flooding likely
Valid 231800Z - 240000Z
SUMMARY...Isolated to scattered instances of flash flooding will
be likely this afternoon and into at least the early evening hours
as showers and thunderstorms with very heavy rainfall rates
develop and expand in coverage.
DISCUSSION...The early afternoon GOES-E visible satellite imagery
shows an expanding CU/TCU field across much of central and
southern VA down through a large chunk of central and northern NC.
Strong diurnal heating continues across this region, and this
coupled with a moisture-rich boundary layer is already fostering
MLCAPE values of 1500 to 2500 J/kg.
Over the next several hours, showers and thunderstorms will be
developing and expanding in coverage, and the activity especially
across areas of south-central to southeast VA and possibly
north-central NC may become locally focused given a corridor of
stronger low-level convergence coinciding with greater boundary
layer instability. The region more broadly is also under some
influence of weak right-entrance region upper-level jet dynamics
which will tend to favor at least some weak deeper layer ascent.
Areas farther west across western NC, southwest VA and southeast
WV will also be in an environment conducive for scattered
convection with the aid of differential heating boundaries and
related nearby orographics associated with the higher terrain of
the Appalachians and especially the Blue Ridge. Already, the
latest radar imagery shows convective initiation underway across
these areas.
Given PWs that are on the order of 1.75 to 2 inches from the
Piedmont eastward into the coastal plain (and more regionally
running as much as 2 standard deviations above normal), the
convection that evolves this afternoon and early this evening will
be capable of producing rainfall rates reaching up to 2.5
inches/hour.
Relatively slow cell-motions coupled with eventually a threat for
some cell-mergers may allow for some storm totals by early this
evening to reach upwards of 2 to 4 inches with some spotty 5+ inch
amounts possible. The 12Z HREF guidance favors areas of
north-central NC and especially south-central to southeast VA
including the Hampton Roads vicinity seeing the heaviest rainfall
potential.
Given the rainfall potential and overall moist to locally wet
antecedent conditions, isolated to scattered instances of flash
flooding are generally likely. Urban flash flooding may become a
notable concern again for the I-64 urban corridor from Richmond on
down through the Norfolk/VA Beach vicinity.
Orrison
...Please see www.wpc.ncep.noaa.gov for graphic product...
ATTN...WFO...AKQ...CAE...GSP...ILM...JKL...LWX...MHX...MRX...
RAH...RLX...RNK...
ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...
LAT...LON 38708014 38707858 38257726 38117602 37667540
36917549 35807615 35047732 34767942 35238203
36148279 37348240 38218147
Source:
Weather Prediction Center issues Mesoscale Precipitation Discussion #708 concerning HEAVY RAINFALL...FLASH FLOODING LIKELY---------------
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