AWUS01 KWNH 310823
FFGMPD
NCZ000-311400-

Mesoscale Precipitation Discussion 1014
NWS Weather Prediction Center College Park MD
423 AM EDT Thu Aug 31 2023

Areas affected...eastern North Carolina

Concerning...Heavy rainfall...Flash flooding likely

Valid 310820Z - 311400Z

Summary...Flash flooding is likely to continue in the short term
across portions of eastern North Carolina, including the Outer
Banks. Significant impacts from flash flooding will remain
possible, though peak rainfall rates of 2-3 in/hr will gradually
lower into the 1-2 in/hr range through 14Z.

Discussion...08Z surface observations placed Tropical Storm Idalia
just offshore of the southern North Carolina coast, with a brisk
movement toward the northeast. Trends in infrared satellite
imagery showed the coldest cloud tops over far eastern North
Carolina, racing northeastward. Since 05Z, rainfall rates greater
than 1 in/hr have been located within about 50 miles of the North
Carolina coast with the highest rainfall rates occurring along the
coast from near North Topsail Beach to the Outer Banks, south of
Hatteras. It is along the coast where two distinct feeder bands
have been interacting with a coastal front, with mini supercells
in the vicinity of Hatteras at 0730Z, supporting slow moving and
repeating rounds of heavy rain. Observed rainfall totals of 3-4
inches in 2 hours have occurred along the coast along with areas
of ongoing flash flooding.

Over the next 6 hours, Idalia is expected to begin more of an
eastward translation, continuing to focus the greatest low level
convergence near the Outer Banks, co-located with the greatest
instability of an estimated 500 to 1000+ J/kg MLCAPE (08Z SPC
mesoanalysis). After roughly 12Z, rainfall rates are expected to
fall below 2 in/hr as Idalia begins to move father away from the
coast. However, in the short term, continued rainfall rates of 2-4
inches in about 2 hours time will support rapid rises and
exacerbate any ongoing areas of flooding. Additional rainfall
totals of 3-6 inches are expected through 14Z, continuing the
likely threat for additional flash flooding, with significant
impacts remaining possible prior to Idalia departing farther
offshore.

Otto

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

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

LAT...LON 36157575 36117512 35777481 35067474 34577543
33987685 33797785 33987827 34717879 35867717


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