• Heavy Rain/Flooding NC/SC

    From Dumas Walker@21:1/175 to All on Fri Jul 26 09:24:00 2024
    AWUS01 KWNH 261353
    FFGMPD
    NCZ000-SCZ000-261852-

    Mesoscale Precipitation Discussion 0734
    NWS Weather Prediction Center College Park MD
    953 AM EDT Fri Jul 26 2024

    Areas affected...South-Central to Southeast NC...North-Central to
    Northeast SC

    Concerning...Heavy rainfall...Flash flooding possible

    Valid 261352Z - 261852Z

    SUMMARY...Slow-moving and very efficient convection with high
    rainfall rates will be impacting areas of south-central NC into
    north-central and northeast SC going through midday. Eventually
    areas of southeast NC will also get into some of this activity
    this afternoon. Some flash flooding is possible.

    DISCUSSION...A very small-scale low-level circulation and
    associated vort center is situated near the NC/SC border region
    which is yielding some low-topped and extremely efficient
    convection across areas of south-central NC and especially areas
    of north-central SC. There is also evidence of a surface trough
    axis extending eastward ahead of the weak low down across
    northeast SC and some adjacent areas of southeast NC.

    At least modest, but persistent moisture convergence along this
    trough axis ahead of the low center along with a gradual increase
    in boundary layer instability via the diurnal heating cycle should
    facilitate a persistence and localized expansion of convection
    going through the early afternoon hours. There is already a bit of
    an instability gradient oriented in close proximity to this trough
    from northeast SC into southeast NC where MLCAPE values are as
    high as 1000+ J/kg.

    The 12Z RAOB data from CHS and ILM show a deep tropical
    environment with tall/skinny CAPE profiles. This will strongly
    support a highly efficient warm rain set-up for very heavy
    rainfall rates that will be capable of reaching 2 to 3 inches/hour.

    Outside of the recent HRRR guidance, the early morning guidance is
    not exactly handling the ongoing activity particularly well.
    However, with the current radar and satellite trends, and slow cell-motions/efficient rainfall set-up, some localized storm
    totals reaching 3 to 5 inches will be possible going through early
    this afternoon.

    Some areas of flash flooding will be possible as a result, and
    especially with some areas already seeing moist antecedent
    conditions.

    Orrison

    ATTN...WFO...CAE...GSP...ILM...RAH...

    ATTN...RFC...SERFC...NWC...

    LAT...LON 35207976 35067890 34547870 34237946 34268042
    34588086 34908083 35118045
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  • From Dumas Walker@21:1/175 to All on Mon Sep 16 08:38:00 2024
    AWUS01 KWNH 160901
    FFGMPD
    NCZ000-SCZ000-161500-

    Mesoscale Precipitation Discussion 1019
    NWS Weather Prediction Center College Park MD
    500 AM EDT Mon Sep 16 2024

    Areas affected...Southeast NC...Northeast SC

    Concerning...Heavy rainfall...Flash flooding possible

    Valid 160900Z - 161500Z

    SUMMARY...Heavy rainfall associated with Potential Tropical
    Cyclone Eight will be advancing inland this morning across
    southeast NC and northeast SC. A gradual increase in the threat
    for flash flooding can be expected as rainfall rates increase.

    DISCUSSION...The latest GOES-E Proxy Visible satellite imagery
    along with radar and aircraft data shows the low center of
    Potential Tropical Cyclone Eight centered approximately 95 miles
    east-southeast of Charleston, SC at 09Z (5AM EDT). The storm
    continues to advance slowly off to the northwest, and this will be
    allowing for heavy rainfall focused around the northern quadrant
    of the storm to begin cyclonically wrapping inland across the
    coastal plain of southeast NC and northeast SC this morning.

    The system still has a fair amount of baroclinicity associated
    with it for the time being given the proximity of multiple frontal
    features, but radar imagery shows pockets of very strong
    convection north of the low center with extremely heavy rainfall
    rates. This is also where there is much greater instability and
    the latest RAP analysis confirms MLCAPE values of as much as 1500
    J/kg near and to the northeast of the center where some of the
    colder convective tops are noted.

    Much more stable air is still noted along the immediate coastal
    plain of the Carolinas, and this will tend to keep rainfall rates
    a bit limited in the short-term across these areas as rains
    offshore gradually push inland. However, in time as stronger
    onshore flow arrives and the low center approaches by later this
    morning, there should be an influx of greater instability and
    stronger moisture convergence that will be conducive increasing
    rainfall rates.

    The 00Z HREF guidance supports rainfall rates in the 12Z to 15Z
    time frame reaching 1 to 2 inches/hour across especially the
    coastal areas of southeast NC around the Wilmington, NC vicinity.
    Some of these heavier rainfall rates may also spread into
    northeast SC near and to the north of Myrtle Beach.

    Expect rainfall amounts by 15Z (11AM EDT) to reach as high as 2 to
    4 inches with isolated amounts potentially up to around 5 inches.
    These rains will gradually increase the threat for flash flooding
    by later this morning.

    Orrison

    ATTN...WFO...ILM...MHX...RAH...

    ATTN...RFC...SERFC...NWC...

    LAT...LON 34667791 34667738 34437729 34177765 33837785
    33777842 33407907 33557953 33917961 34177945
    34357913 34487867
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