As of 300 AM Wednesday...
*
Scattered flash-flooding is expected this afternoon through late
this evening, especially in urban areas of the Piedmont (including
the Triad) as well as the hydrological sensitive areas of the
eastern Piedmont from Chantal
rainfall.
*
Flood Watch in effect for a majority of the central
NC Piedmont
and western Sandhills from 2 PM today until 2 AM tonight.
Convectively amplified shortwaves are expected to ripple through the
base of the broad mid/
upper level trough currently stretching from
the Great Lakes through the Ohio Valley and into the ArkLaTex
region. This will result in weak but gradual
H5 heights falls to
leak into the Mid-Atlantic this afternoon through the overnight
period. Anomalous deep layer
moisture will gradually increase to
around 2" areawide (exceeding the 90th percentile) and prime the
area for efficient heavy
rainfall showers/storms during the
afternoon. Showers and storms are expected to develop along the
eastern slopes of the mountains and over western
NC and gradually
shift eastward into central
NC through mid-afternoon.
The
likely greatest concern through tonight will be for
scattered
instances of
flash-flooding this afternoon through late this
evening. Anomalous deep-layer
moisture, weak
steering winds, a deep
warm-
cloud layer >10,000
ft, and moderate to strong
instability are
all very favorable ingredients for
flash-flooding. Additionally, the
eastern Piedmont is still hydrological sensitive due to
rainfall
from Chantal (soil
moisture still 50-70% and
FFG of around 2.5" in 6
hours). 00z HREF and the 18z REFS continue to indicate 40 to +60%
probabilities for >3" in 24 hours, but investigating the LPMM
fields, these areas of locally enhanced
rainfall will
likely be
scattered in nature in concentrated areas. The limited coverage of
these amounts in available guidance precludes higher probabilities
for
flash-flooding at this time. Observational trends will be
assessed through this afternoon whether a moderate risk for excessive
rainfall (Level 3 out of 4) will be needed. Finally, even with
continued weak synoptic support for showers/storms to continue
overnight, available guidance still shows a noticeable weakening
trend to convective intensity from 03-06z. As such, will opt to not
extend the
Flood Watch through the overnight hours at this time.
